Air conditioning retrofit

[kmead]

Somehow I didn't pay any attention to this when it was current - I love the work you did custom fitting the new controls into stock panel, etc. and your custom air duct manifold. I identify with the labor involved there - I have done similar fab work for other things used ABS, etc., I bought a plastic weld kit which makes that process easier (if smelly).

Looks like I need to get the Hurricane unit & go back to including AC in my build. I have been vacilitating on this. Since I already have AC and have already done the LArryC Condensor, etc, much of it will be more straightforward. I'm doing a custom dash a' la Clark, so I'll not worry about any of the ducting, etc., until much later.

Thanks for the awesome photo documentation, as always!

Hussein, if you already have the existing AC system, why do you need to modify it beyond changing the soft lines and putting in a new dryer?

Asking because I am confused about why changing the HVAC in car system would need to be done to do all this given that the OE condenser and evaporator are 134a compatible.

The existing heater valve could be supplemented by a bypass valve in the engine bay or replaced by a manual version controlled by the existing cable in Rodger’s position to maintain the way the Honda thermostat is looking for flow to occur.

The existing ducting across the car effectively is what Rodger mimicked. Given you are looking at a custom dash, deleting this and going to outside air corner ducts (as in a non AC X system) with just the defrost, floor and center ducts providing conditioned air would likely be more than sufficient given the size of the cabin.

From the statements Rodger makes the Fiat HVAC unit is more compact than the Hurricane unit so just curious about your thinking.

My ‘new’ X has air and is also looking to have an alternative engine upgrade so just trying to learn as I will be facing a similar issue in my future.

 

[Rodger]

Somehow I didn't pay any attention to this when it was current - I love the work you did custom fitting the new controls into stock panel, etc. and your custom air duct manifold. I identify with the labor involved there - I have done similar fab work for other things used ABS, etc., I bought a plastic weld kit which makes that process easier (if smelly).

Looks like I need to get the Hurricane unit & go back to including AC in my build. I have been vacilitating on this. Since I already have AC and have already done the LArryC Condensor, etc, much of it will be more straightforward. I'm doing a custom dash a' la Clark, so I'll not worry about any of the ducting, etc., until much later.

Thanks for the awesome photo documentation, as always!

If you already have AC, I would suggest trying to stay with the stock evaporator/heater unit as it fits with no need for mods. I think it would be possible to get rid of all the miscellaneous valves and upgrade the system to a more modern simpler layout. It may also be possible to get rid of the vacuum actuators and convert to the servos like I did. Basically the Hurricane system but with the stock box.

 

[Dr.Jeff]

I have been upgrading the stock AC system by doing as Rodger suggests; eliminating the original pressure control and 'freeze up' switches in favor of a trinary switch, and rewiring the relay control for the compressor and fans. A new high-efficiency parallel-flow condenser (as you have already done), new receiver/dryer, and new hoses to match everything up (new Sanden compressor in my case, Honda stuff in yours). No need to change out the heat/AC box, air ducts, etc. I do recommend flushing the evap and replacing the expansion valve. And I agree with Rodger that the stock vacuum actuated controls are not very good. I'm considering improvements on that later. I'm also changing the heater valve to a VW style. So there is still plenty of work to do. I suppose if you are making the 308 style custom dash then it might not be much more work to replace the box. But I really don't think it will be any more effective than reviving the old box.

 

[kmead]

I have been thinking that changing the vacuum controller to a cabled system from the non AC hvac would also do the trick with a switch for ac as Rodger has done would be a nice alternative.

 

[Dr.Jeff]

I have been thinking that changing the vacuum controller to a cabled system from the non AC hvac would also do the trick

I haven't looked at it too closely yet. Does it seem pretty straight forward or will it involve a lot of mods?

The rotary switch for the temp control is a very standard part, available inexpensively (less than $10 online). It has a probe attached that is clipped over one of the evap tubes:

 

[lookforjoe]

Hussein, if you already have the existing AC system, why do you need to modify it beyond changing the soft lines and putting in a new dryer?
My ‘new’ X has air and is also looking to have an alternative engine upgrade so just trying to learn as I will be facing a similar issue in my future.

1) It's a crappy system. 2) It's 30 years old. The heater core & evaporator will need servicing at some point. I'd rather go with a more modern setup. I already replaced the Condensor, expansion valve & Reciever/Drier, and have an external heater valve. Reason is not tied to motor swap

If you already have AC, I would suggest trying to stay with the stock evaporator/heater unit as it fits with no need for mods. I think it would be possible to get rid of all the miscellaneous valves and upgrade the system to a more modern simpler layout. It may also be possible to get rid of the vacuum actuators and convert to the servos like I did. Basically the Hurricane system but with the stock box.

Nah, I'll replace it. I don't want to retain the stock setup with my new dash, every aspect of the duct work needs revision & the unit is not efficient at all. Needing to mod for install is never a deterrent

 

[Rodger]

Just finished getting rid of the Photobucket links in this thread. It was kind of fun going back through it as one tends to forget all of the futzing that went into it. I figure that one day when I am too old for this car, I can pass on the links to the build for the next owner.

I am also in the very gradual process of refurbishing all of the stock AC system parts that I got off of my '86 parts car to be installed on my '79, eventually. Any more comments about what others have done/are doing to make the stock system simpler and more modern would be greatly appreciated. I know that @lookforjoe and @Dr.Jeff have done some work in this department. Please post any links to your threads that would be appropriate. Thanks!

 

[Dr.Jeff]

Rodger, my take is to use the following stock Fiat AC parts: the compressor mounting brackets for the engine, and the AC/heater box (with evaporator) under the dash with accompanying controls. If you also have the alternator/brackets/pulleys/water pump assembly then that may be easier than trying to rig up a drive belt for the compressor otherwise. The rest gets tossed out.

I recommend a universal Sanden 508 compressor (fits the stock mounting brackets), a universal parallel flow condenser, a universal receiver/dryer with trinary switch, universal barrier hose and fittings to match your new components, and a generic expansion valve that fits the X's evaporator. And thoroughly flush the evaporator and clean the fins on it (as you rebuild the heater box). You can make a simple wire harness that connects the dash switch, trinary switch, electric fan, and the compressor by way of a standard relay.

The hoses can be made up at a local shop or you can do them yourself if you get a crimping tool. Everything is available online inexpensively by choosing universal components rather than trying to replace the factory stuff directly. Get the largest condenser that will fit the radiator and largest receiver/dryer that you can fit under the hood.

Basically the entire system will be brand new (except the evaporator), extremely more efficient, and much more reliable than the factory setup. For the tiny air volume in the X's cabin it will be too cold most of the time.

 

[Rodger]

Rodger, my take is to use the following stock Fiat AC parts: the compressor mounting brackets for the engine, and the AC/heater box (with evaporator) under the dash with accompanying controls. If you also have the alternator/brackets/pulleys/water pump assembly then that may be easier than trying to rig up a drive belt for the compressor otherwise. The rest gets tossed out.

I recommend a universal Sanden 508 compressor (fits the stock mounting brackets), a universal parallel flow condenser, a universal receiver/dryer with trinary switch, universal barrier hose and fittings to match your new components, and a generic expansion valve that fits the X's evaporator. And thoroughly flush the evaporator and clean the fins on it (as you rebuild the heater box). You can make a simple wire harness that connects the dash switch, trinary switch, electric fan, and the compressor by way of a standard relay.

The hoses can be made up at a local shop or you can do them yourself if you get a crimping tool. Everything is available online inexpensively by choosing universal components rather than trying to replace the factory stuff directly. Get the largest condenser that will fit the radiator and largest receiver/dryer that you can fit under the hood.

Basically the entire system will be brand new (except the evaporator), extremely more efficient, and much more reliable than the factory setup. For the tiny air volume in the X's cabin it will be too cold most of the time.

Great, thanks! That was kind of what I was thinking. I was struck by how simple the Hurricane system was that I used for my K20, compared to all of the various valves and relays of the stock AC system. My thought was to try and duplicate it, but with the stock evaporator. What do you flush the evaporator with?

 

[Dr.Jeff]

The factory setup is very odd and not very efficient. Old design, but even then it is strangely configured. The Hurricane and most other systems available utilize a trinary switch in lieu of all those gizmos on the X's stock system.

They make a specific flushing agent for AC systems. However since you will have the evaporator completely isolated and are only flushing it, you really don't need the specific stuff. But it can't be certain solvents because any residual can react with the refrigerant. The one that works well and won't harm anything is common mineral spirits.

I'm sure you will research it all online, but I have notes on the system layout, hose and fitting sizes, wire diagram, and should even be able to find the part numbers for the components I used if you need any of it.

 

[Rodger]

Ok. If I get stuck I’ll reach out. It is a ways off at this point.

 

[lookforjoe]

Just finished getting rid of the Photobucket links in this thread. It was kind of fun going back through it as one tends to forget all of the futzing that went into it. I figure that one day when I am too old for this car, I can pass on the links to the build for the next owner.

I am also in the very gradual process of refurbishing all of the stock AC system parts that I got off of my '86 parts car to be installed on my '79, eventually. Any more comments about what others have done/are doing to make the stock system simpler and more modern would be greatly appreciated. I know that @lookforjoe and @Dr.Jeff have done some work in this department. Please post any links to your threads that would be appropriate. Thanks!

This is the "bible" of AC threads by LarryC. -I would use this a guide for all refurbishment.

In my case, I ditched the receiver/dryer & orifice tube setup - which IMO are the real failings of the old setup in terms of efficiency. The problem on a stock X would be figuring out where to put the accumulator in the engine bay, as it needs to connect to the compressor low side. The receiver/dryer just gets eliminated & replaced with the orifice tube setup. The expansion valve has to be gutted, and used as a simple elbow fitting. The links to my adaptations are spread throughout my K24 install thread

 

[Rodger]

Even though I had the AC system finished on my K20 for some time, I held off actually charging the system for a couple of reasons. One, I wanted to drive the car for a while to make sure everything stayed together, which so far it has. I did have to disconnect the dryer when I was attaching the mounting brackets for my front sway bar, so it was good it wasn't charged. Two, and the biggest reason, was fear. If it didn't charge and work as hoped, I wasn't sure I could take the disappointment and having to figure out what I did wrong. Plus, I had never charged an AC system before, but when has not knowing how to do something stopped me. This whole build was about learning new things.

But with summer upon us and 113 degrees here last week, it was time. I watched a couple of YouTube videos on charging an AC system and got a gauge set from HF and gave it a go. I pulled a vacuum for an hour or so, then slowly added the refrigerant. The compressor solenoid kicked in as the pressure rose, which was a great relief. I continued to add refrigerant but wasn't really sure how to tell how much to add, but then it just stopped taking more. The pressures weren't as high as the charts I found, but there is nice cold air coming out of the dash vents, so I guess it works. Another project complete!

 

[kmead]

Congrats on yet another job well done.

I presume you picked up the vacuum pump at HB as well?

 

[Rodger]

Congrats on yet another job well done.

I presume you picked up the vacuum pump at HB as well?

I had a couple of old vacuum pumps laying around at my office. I have had my own dental lab for years. When you fire porcelain for crowns, you have to pull a vacuum. The furnaces come with some very nice vacuum pumps that last forever. I had kept them even though we retired the furnaces years ago.

 

[Dr.Jeff]

I continued to add refrigerant but wasn't really sure how to tell how much to add

This is a difficult thing to know when a custom system is built with a unknown total capacity. The current standard is by weighing the volume of refrigerant added, but in these cases that's not possible because there is no spec to follow. You can try to get the spec for each component and calculate the volumes, but I've never been able to do that. The old school method of using pressures is good but not always as accurate. Same with having a "window" and looking for the bubbles to disappear. I've been told another approach is to use a contactless thermometer to monitor the temperature at the exit of the evaporator and inlet of the compressor. When those two points reach the same temperature the system is full (honestly I do not have a good explanation for this method, but supposedly it works). The problem is often you cannot gain good access to those two points, especially while doing all the other tasks involved in filling a system. So I usually rely on monitoring pressures.

If you haven't reached the desired pressure yet, but it doesn't seem to want to take any more refrigerant, try warming up the can of refrigerant in a bucket of hot water as you add it. Also swap to a new can of refrigerant if the one you are using is less than half full; the new can will have more pressure inside to help it transfer to the system. However too much refrigerant (pressure) has the same effect as too little refrigerant (pressure), so knowing when to quit may take some trial experimentation.

 

[Rodger]

Projects like this always seem to evolve as you drive the car more and find things that don't quite work the way you thought. Hussein, @lookforjoe, can probably testify to this. The heat and AC was working fine, but on my way back home from Italian Day at Griot's, I happened to rest my hand on the console and I thought it felt pretty warm. At first I thought it was because the sun was out, but nothing else in the interior was that warm. The more I drove, it stayed quite warm but nothing else. I had the heat turned off, so it was not coming from the heater core, but when I got home, I reached into the tunnel by the gas pedal and found that the pipes to the heater valve were very hot.

The Hurricane system I used, comes with an electronic bypass valve for the heater. I never really thought about it much and just followed the directions on how it works and installed it per the manufacturer.

These aftermarket systems are primarily designed for front engine vehicles and so apparently the valve would normally be located somewhere in the engine compartment. I decided to put mine close to the heater core as it fit nicely there. To put it in the engine bay would have required to cram one more thing in the already stuffed cooling system, plus the wiring harness as it comes, was too short to reach, so I would have had to splice in more length. What I never thought about is that when the valve is "closed", it actually allows coolant to circulate in the pipes to and from the engine. When you open the valve, then coolant is directed into the heater core. It does provide "instant" heat, but because the coolant is always circulating in the pipes, those get hot and one of them runs inside the tunnel, which heats it up and that heat is what I was feeling through the console.

I realized that I really needed just an on-off valve like the stock install, not a bypass style. Old Air, who makes the Hurricane, does not offer just an on-off from what I can find on their website. I called them and they said that the only sell the bypass style as so many of their systems are used on LS-1 swaps which require a bypass circuit. I looked at the one from Vintage Air that Hussein, @lookforjoe, had shown in his thread but wasn't 100% sure that the electronics are the same as my system. The picture of it on the Vintage website only shows it from one view so it is hard to see if it is the same servomotor box or not, but it looks very similar. I asked Old Air if a valve from a competitor might work and if they happen to buy their valves from some outside source. They said the one from Vintage would not work with their system. I assume that most of these aftermarket AC companies source their electronic valve motors from a common manufacturer, but elected to try and work with the valve I already had, plus I already had the plumbing laid out for my valve.

I decided to just get some bypass caps from my local O'Reilly's and capped off the valve outlet and heater outlet fittings, then connected the outlet pipe from the heater core to the return pipe in the car. Basically, I tried to turned it into an on-off valve.

I was a little concerned it might not work as I had hoped, since when I had it out of the car, I tried blowing into the inlet pipe from the engine with the valve closed and I could feel a little air leaking from the outlet going to the heater core, but I figured I would give it a try. The hardest thing was getting positioned on my back under the steering column to reach all of the hose clamps so I could remove the valve. The valve is located right above where the metal heater pipes come up out of the tunnel next the gas pedal. Of course, I removed the driver's seat, but it was still quite a contortion to get into position on my back, try and see upside down what I was doing, then extricate myself at each step. Sucks to get old. Fortunately, when I did the original install, I had angled the worm screws on the clamps to face toward the opening above the gas pedal, so at least I could get a nut driver on them. Here are photos of how I had it originally plumbed and then my changes.

As some of you may guess, that little bit of leaking air turned into cooling leaking into the heater core even with the valve off. So with the fan running, I was getting warm air. It wasn't hot, but I didn't want any warmth if I didn't need it, plus the console got warm again. Back to the drawing board.

I messaged Hussein and asked if he had ordered the valve kit from Vintage and he had just gotten it. He sent me a photo of the motor side of the valve where the connector plugs in and I immediately knew it was the same motor. If you look at the photo above, you can see an embosssed logo on the motor body but someone had ground off something to the right of the logo. Turns out it was the name of the company that made the valve. Newbase Auto Electronics. There was even a stamped data plate on it that had the company website, www.newbasecn.com. It is a company in China that makes a lot of auto electronic parts. I looked at their website and found the electronic heater valve. Turns out it comes in several versions depending on how you want to control the valve. My valve from Old Air has five wires, the same as the one that Hussein had. I called Vintage Air and ordered just the 5 wire valve as I did not need the whole controller kit. Here are pictures of the Vintage valve on the left and the Old Air one on the right.

The first thing I did was to unplug the control wires from my valve and plugged them into the Vintage valve. I knew my controls would operate the valve, the only thing I didn't know was if it would go from closed to open when I slid my lever to the heat position. Just my luck, it was opposite from what I needed. When my heat lever is slid to the left, i.e. full hot, the valve would close. So that meant I need to reverse the wires on my slider or at the motor somehow. Unfortunately, there are five wires going into the servomotor and I had no way to know which was which. When I was making my custom controls with the sliding rheostats out of the Old Air control panel, I got one of them the wrong way, so I had to unsolder the wires and switch them. I described this earlier in this thread. Unfortunately, there was no way to get access to the back of the sliders without totally disassembling the dash to get the heater controls out.

I knew there was a three pin connector coming from the rheostat that plugged into the Hurricane wiring harness and I was just able to get to that by removing the radio and the gauge cluster. That allowed me to just get my fingers in there to disconnect the connector.

The contacts in these connectors are held in by little finger springs that engage the side of the holes in the connectors. They are a pain to try and release, but my plan was to try and get the black and brown connectors out and switch them as they come from each side of the rheostat. These contacts actually had one finger spring on each side of the pins. I made a couple of release tools from paper clips that I ground down flat and then slid in on each side of the contact which released them. I then swapped the brown and black, then plugged the connector back together and tested it. Success! Now the valve operated the way the slider indicates.

Now all I had to do was drain the coolant (again!), take the seat out (again!), and crawl back in there to swap out the valve. Here is it installed and it works perfect! Great heat only when I want it and it is infinitely controllable as to the temperature.

I like this valve so much, that my plan when I retrofit my '79 with a modified stock X1/9 evaporator unit is to use this valve instead of the unobtanium and hard to get to stock mechanical valve. I plan to get rid of the lever that pushes the cable to the valve and do the same thing I did with this install. Mount a sliding rheostat in the slot for the heater control and get rid of the cable and it's issues altogether as well as having a reliable electronic heater valve.

 

[Dr.Jeff]

Projects like this always seem to evolve as you drive the car more and find things that don't quite work the way you thought. Hussein, @lookforjoe, can probably testify to this. The heat and AC was working fine, but on my way back home from Italian Day at Griot's, I happened to rest my hand on the console and I thought it felt pretty warm. At first I thought it was because the sun was out, but nothing else in the interior was that warm. The more I drove, it stayed quite warm but nothing else. I had the heat turned off, so it was not coming from the heater core, but when I got home, I reached into the tunnel by the gas pedal and found that the pipes to the heater valve were very hot.

The Hurricane system I used, comes with an electronic bypass valve for the heater. I never really thought about it much and just followed the directions on how it works and installed it per the manufacturer.

View attachment 52592


These aftermarket systems are primarily designed for front engine vehicles and so apparently the valve would normally be located somewhere in the engine compartment. I decided to put mine close to the heater core as it fit nicely there. To put it in the engine bay would have required to cram one more thing in the already stuffed cooling system, plus the wiring harness as it comes, was too short to reach, so I would have had to splice in more length. What I never thought about is that when the valve is "closed", it actually allows coolant to circulate in the pipes to and from the engine. When you open the valve, then coolant is directed into the heater core. It does provide "instant" heat, but because the coolant is always circulating in the pipes, those get hot and one of them runs inside the tunnel, which heats it up and that heat is what I was feeling through the console.

I realized that I really needed just an on-off valve like the stock install, not a bypass style. Old Air, who makes the Hurricane, does not offer just an on-off from what I can find on their website. I called them and they said that the only sell the bypass style as so many of their systems are used on LS-1 swaps which require a bypass circuit. I looked at the one from Vintage Air that Hussein, @lookforjoe, had shown in his thread but wasn't 100% sure that the electronics are the same as my system. The picture of it on the Vintage website only shows it from one view so it is hard to see if it is the same servomotor box or not, but it looks very similar. I asked Old Air if a valve from a competitor might work and if they happen to buy their valves from some outside source. They said the one from Vintage would not work with their system. I assume that most of these aftermarket AC companies source their electronic valve motors from a common manufacturer, but elected to try and work with the valve I already had, plus I already had the plumbing laid out for my valve.

I decided to just get some bypass caps from my local O'Reilly's and capped off the valve outlet and heater outlet fittings, then connected the outlet pipe from the heater core to the return pipe in the car. Basically, I tried to turned it into an on-off valve.
View attachment 52593

I was a little concerned it might not work as I had hoped, since when I had it out of the car, I tried blowing into the inlet pipe from the engine with the valve closed and I could feel a little air leaking from the outlet going to the heater core, but I figured I would give it a try. The hardest thing was getting positioned on my back under the steering column to reach all of the hose clamps so I could remove the valve. The valve is located right above where the metal heater pipes come up out of the tunnel next the gas pedal. Of course, I removed the driver's seat, but it was still quite a contortion to get into position on my back, try and see upside down what I was doing, then extricate myself at each step. Sucks to get old. Fortunately, when I did the original install, I had angled the worm screws on the clamps to face toward the opening above the gas pedal, so at least I could get a nut driver on them. Here are photos of how I had it originally plumbed and then my changes.
View attachment 52594View attachment 52595View attachment 52596

As some of you may guess, that little bit of leaking air turned into cooling leaking into the heater core even with the valve off. So with the fan running, I was getting warm air. It wasn't hot, but I didn't want any warmth if I didn't need it, plus the console got warm again. Back to the drawing board.

I messaged Hussein and asked if he had ordered the valve kit from Vintage and he had just gotten it. He sent me a photo of the motor side of the valve where the connector plugs in and I immediately knew it was the same motor. If you look at the photo above, you can see an embosssed logo on the motor body but someone had ground off something to the right of the logo. Turns out it was the name of the company that made the valve. Newbase Auto Electronics. There was even a stamped data plate on it that had the company website, www.newbasecn.com. It is a company in China that makes a lot of auto electronic parts. I looked at their website and found the electronic heater valve. Turns out it comes in several versions depending on how you want to control the valve. My valve from Old Air has five wires, the same as the one that Hussein had. I called Vintage Air and ordered just the 5 wire valve as I did not need the whole controller kit. Here are pictures of the Vintage valve on the left and the Old Air one on the right.
View attachment 52597
View attachment 52598

The first thing I did was to unplug the control wires from my valve and plugged them into the Vintage valve. I knew my controls would operate the valve, the only thing I didn't know was if it would go from closed to open when I slid my lever to the heat position. Just my luck, it was opposite from what I needed. When my heat lever is slid to the left, i.e. full hot, the valve would close. So that meant I need to reverse the wires on my slider or at the motor somehow. Unfortunately, there are five wires going into the servomotor and I had no way to know which was which. When I was making my custom controls with the sliding rheostats out of the Old Air control panel, I got one of them the wrong way, so I had to unsolder the wires and switch them. I described this earlier in this thread. Unfortunately, there was no way to get access to the back of the sliders without totally disassembling the dash to get the heater controls out.

I knew there was a three pin connector coming from the rheostat that plugged into the Hurricane wiring harness and I was just able to get to that by removing the radio and the gauge cluster. That allowed me to just get my fingers in there to disconnect the connector.
View attachment 52599

The contacts in these connectors are held in by little finger springs that engage the side of the holes in the connectors. They are a pain to try and release, but my plan was to try and get the black and brown connectors out and switch them as they come from each side of the rheostat. These contacts actually had one finger spring on each side of the pins. I made a couple of release tools from paper clips that I ground down flat and then slid in on each side of the contact which released them. I then swapped the brown and black, then plugged the connector back together and tested it. Success! Now the valve operated the way the slider indicates.

Now all I had to do was drain the coolant (again!), take the seat out (again!), and crawl back in there to swap out the valve. Here is it installed and it works perfect! Great heat only when I want it and it is infinitely controllable as to the temperature.
View attachment 52600

I like this valve so much, that my plan when I retrofit my '79 with a modified stock X1/9 evaporator unit is to use this valve instead of the unobtanium and hard to get to stock mechanical valve. I plan to get rid of the lever that pushes the cable to the valve and do the same thing I did with this install. Mount a sliding rheostat in the slot for the heater control and get rid of the cable and it's issues altogether as well as having a reliable electronic heater valve.

Rodger, excellent research finding the maker of the valve and a replacement model that works with your system.

This doesn't directly pertain to your situation, but speaking of hot coolant circulating through the pipes when the valve is closed, there are valves (of various styles and types) that never completely close off the flow. I am not referring to "bypass" valves like you had, but standard shut off valves with one inlet and one outlet. Even when they are in the fully closed position these valves are designed to allow some coolant to pass. In other words they intentionally "leak" internally and never fully close. My understanding is this supposedly helps prevent corrosion in the heater core and the valve by eliminating stagnant coolant. However it also has the effect you found, heat transferring through the system, even when it is off. As you say, on some types of vehicles that doesn't make much difference. But on other cars, like the X, that heat is felt inside the cabin. The problem is the valve manufacturers do not label the valves as such, so you will have no way of knowing that this will happen until you either test it or install it. I've often wondered if any of the various generic valves that have been suggested as a replacement for the stock X heater valve have this feature.

Great work getting your system sorted again.