Heater Control Valve Mod

lookforjoe

True Classic
When I got this X last year, the PO had added a manual valve under the '"hood" to replace the broken internal heater valve. Tired of getting in & out of the car to turn the heat on & off (especially now with the ambient temps all over the place.

Found a way to stick some more Volvo parts in my X :D....

700 series heater control valve, Evap solenoid from 900 series, ran wiring to one of the blank switches on the console for solenoid power. I tried using a rheostat to modulate the solenoid, and bleed off vacuum, but the soleniod is only on/off, drop below 12v & it just shuts off.

9htrValve.jpg


X19HtrValveMod0004.jpg


X19HtrValveMod0001.jpg


X19HtrValveMod0002.jpg


X19HtrValveMod0003.jpg
 
Nice work

I tried using a rheostat to modulate the solenoid, and bleed off vacuum, but the soleniod is only on/off, drop below 12v & it just shuts off.

Yep, this is normal. The only way that you can get a "variable" solenoid is to use one which has either PWM control or is actually a stepper motor. Typically these are used in idle control systems in more modern cars (where the X uses a mechanical auxiliary air valve). Either way, it will require a relatively complex drive circuit.

Cheers,
Dom.
 
VW parts

My heater valve rusted and started leaking within about a year after I bought my car. I noticed it was made of metal, so I figured if I bought a new one it would just rust out too.

So I used the all-plastic rotary ball heater valve from a (late 1970's; though I'd imagine they used the same one for many years after) VW Rabbit. Hose size was compatible and so was the control cable. It's been a long time so I can't be sure I remember correctly, but I don't think I had to make any mods for this substitution.

The stock location for the heater control valve is under the dashboard on the passenger (LHD) side.
 
Something like this?
Heater_valve.jpg


Isn't the OEM one bolted to flanges (I don't know, I only looked at mine briefly). I going to try and free it up with brute force first.
 
That looks familiar! :)

I did this -literally- more than 20 years ago, and really haven't looked at it much since, but the picture definitely seems right!

The hoses and the control cable are stiff enough that it can just hang there. Depending on how your hoses lay, it might need a zip tie to hold it tidy, but shouldn't need more than that.
 
I think mine is like this
1820a_fiat_heater_valve.jpg


Right angle and (by the look of it) bolted to flanges, not sure if there's even hoses to connect to coming and going, but I'll have to look closer. The price sure is right, about $5 for a VW plastic non corrosive one VS. $35+ for OEM.
 
My car has AC - the valve is integral to the core, I believe a generic inline won't work in the stock location - hence the engine bay mod.
 
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