Maximizing air pressure from non-AC, 1974 heater block.

tvmaster

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Me again. Heater / air question. The heater works, seems to have two speeds: loud and louder. There is some air movement on all three locations: defrost / cabin / floor, but the volume of air being moved doesn’t equal the noise it makes.
Are there simple solution? Taping something up, creating a tunnel, forcing more air to the three vent areas?
Seems to be working awfully hard for the end result.
Or is this just normal...
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It should blow a reasonable amount of air. Note that you can choose to have it come out on the floor or through the center dash vents if open or through the defrost if the vents are closed or some combination of all depending on how open or closed things are. In that case, the air flow is going to be coming out of a number of different places so the flow rate out of each would be less.

Cars with quiet heaters usually have squirrel cage blowers. The X uses a fan and is not exactly quiet. However, I've been able to stay warm on frigid days with the top off and the windows up so it should put out a fair amount of heat.
 
It should blow a reasonable amount of air. Note that you can choose to have it come out on the floor or through the center dash vents if open or through the defrost if the vents are closed or some combination of all depending on how open or closed things are. In that case, the air flow is going to be coming out of a number of different places so the flow rate out of each would be less.

Cars with quiet heaters usually have squirrel cage blowers. The X uses a fan and is not exactly quiet. However, I've been able to stay warm on frigid days with the top off and the windows up so it should put out a fair amount of heat.
Yeah, the amount of heat is pretty good. Floor air moves the best, defrost, the worst. So are you saying you need to close the dash vents to force more air out the top? What comes out the vents isn’t very strong either - and since there’s no AC, vented air helps. So, it’s likely working the way it was designed?
 
The fan of the non AC cars is pretty loud. The heater should be able to keep you warm with the top off - if everything is working right.
One thing that I've seen that will cause a reduced amount of air flow is leaves and a bunch of crap on top of the heater core. Bad news is that it's a real PITA to remove that stuff which probably means the heater box has to come out. :eek: You might be able to carefully vacuum out some of the crap from under the cowl? I've never attempted it. Good news is that once you've done that a lot of funky smells will go away too.
 
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On your car the outer vents are just air pushed into the cowl area by the car moving through the air, this is why one wants to ensure the cowl area is clean as you will have chunks of leaves etc blow in your face. So the side vents don’t have anything to do with the fan based system.

The first thing is to ensure the cowl vent is open to its maximum. Ensure it is clean up in the cowl. The control should move through its whole distance with nominal resistance. If not then you have another job ahead of you.

The fan is normally loudish. It gets louder if the fan no longer fits properly on the shaft of the motor, the bearings of the motor are perished, and so on.

Another issue can be what is on top of the heater core. In my case (and its likely my spring project) there are olive tree leaves (its from Pasadena) and the remains of a mouse nest on top. It makes for an interesting smell and reduced air flow. In addition on my car the heater valve is also locked so it will be a full R&R.

This means I have to remove the box completely which also means removing the lower console. While I am at it I will do some other electrical upgrades... the slippery slope will be long I am sure...
 
Super info. I indeed took the Dyson stick and got down in the cowl areas, making sure it’s clean. Lucliky, I don’t see any nests either. Hey, when the engine’s chugging away behind you, the heater volume drops in relativity, right?
 
Several thoughts on this:

Based on your description of the blower noises (also posted in other threads), I'm suspicious that your blower motor might be on its way out. But "noisy" is a relative thing, so just a hunch. There have been previous threads about rebuilding or replacing the motor because of this.

I don't know for sure if the '74 is the same, but the blower motor speeds are controlled by a old school "resistor" (looks like a toaster) to reduce the motor's speed by increasing the electrical resistance. I've found that resistor is typically corroded and well worn so the resistance values are triple what they were originally. That means the blower is spinning about a third the speed it used to. When that happens it's time to replace the resistor. We've been discussing the possibility of using a modern style blower resistor pack instead of the old school "fire starter".

Related to that, the (high) amperage that feeds the motor is routed through a lot of circuits/components that don't handle the load well. That's where one of the relay mods helps.

As Karl stated the heater box tends to become very contaminated over the years. I've opened them to find all sorts of disgusting things. Not only was it surprising they worked at all, but a serious health hazard as well. Same for the cowl area - to REALLY clean that area out you may have to remove the wiper assembly, heater resistor, brake reservoirs, etc. In addition the heater box tends to develop other issues, like the control cable mounts break (so the doors don't move very far), or the door pivots break, or the insulation around the edges of the flappers and seams has deteriorated, and more. Need to remove it, clean it, rebuild it.

Even when everything is working correctly these aren't great ventilation systems compared to what you might be accustomed to with more modern cars.
 
Something I forgot to mention, if you take the heater box out, then check to make sure all of the air hoses (vent tubes) are securely in their proper place. I've often found them loose or completely detached, so the air was just blowing into the back side of the dash.
 
Okay, had the X out today with a roof-off, heater-on ride, and the heater worked very nicely. You really don’t hear it in third gear, and it warms the cabin very nicely. Actually quite an enjoyable drive. I’m starting to like this little car quite a lot, even with all it’s dated foibles. Why did we buy it? To say “screw you, Covid - you’ve taken our vacations away, but you won’t take our freedom!”. lol. Now. where’s the blue face-paint.
Sure, it will break a lot and cost a bunch of $$, but we’re putting it down to Covid-19 crazy impulse buying. What the hell.
 
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