Porsche Enthusiasts Club Forum

Hi all,
I have two heater related issues:

1) When I push the recirculation or demist buttons on the dash nothing happens - although it appears as if recirculation is ON - as the fresh air inlet flaps inside the engine bay are up/closed when the car is running.

2) Turning the heat dial doesn't introduce heat into the cabin.

I've checked the heater and mixing valve clips in the passenger footwell and they're both intact. I've tried pushing the control arms but they are not budging.

I checked both solenoids in the drivers footwell by connecting them directly to the battery - both work (ie allow air to flow through them when powered) - and when connected up under the dash they seem to be allowing the vacuum system to operate. So the solenoids must be powered by default correct?

There is vacuum on the supply feed from the engine bay, and through to the valves on the inlet flaps - if I disconnect the hose at the inlet valve the flaps open. Presumably pushing the recirculation switch to OFF (ie out by default) should disengage the solenoid and break the vacuum allowing the flaps to open for fresh air. Pushing the recirculation button does nothing.

I've kept the supply vacuum feed on the Y joint that feeds to both solenoids but swapped the other two hoses around - but no change in the state of the system.

I noticed the heater water valve on the rear of the engine doesn't move and stays in the "AUF" position ie link pushed out when the engine is running.

Under the dash the solenoids share a wiring plug with four connectors. There appears to be a pair of brown thin wires and another pair. Which solenoid should the brown thin wires control (ie the recirculation or heat function)? If I know this then I can connect the hoses to the correct solenoid.

Pushing the recirculation button on the dash doesn't make either solenoid click, nor does turning the heat dial. Perhaps someone could check theirs and let me know if you hear a click in a solenoid when you push the button or turn the dial to heat.

The only function on the control unit that is working is the blower speed dial.

Many thanks if you can assist in sorting this issue out. Any ideas?

I would look at the heater valve, not sure if it is vacuum operated on your car but if so I would check there is a good vacuum at the tube to the valve, you can disconnect the tube and use a large syringe and piece of tube to connect it to the valve then you can test the valve to see if it opens and closes manually with the syringe. It is not unknown for the valve to stop either opening or closing fully as they tend to get very hot and are only made from plastic, so the diaphragm can break down or the seat can pass. I had the opposite problem that mine would not go cold and this was due to the valve not shutting off fully even with full vacuum, I replaced mine with a second hand unit for £10 plus replacement hose connectors.

hi mate let me no how you get on mine is the same the only thing that works is the heater speed

Sounds like you need to replace the heater control valve.

Around $35.00 USD, if I remember correctly, although not the easiest of pieces to get to without removing a few items.

Depends on the model but I agree on my S2 it looked really easy to do but only when you get the hoses and the valve out do you realise it won't go back in. I removed the oil filter when I did mine and it was much easier obviously best to do it when you need to change the oil.

Ah yes, very true.

Earlier models not so bad. Later NA models and the 51/52 trims are more....cluttered...so to speak.

I have got a nice heater valve freshly removed from an S2. Worked fine if you need it??? £10 plus post????
Alasdair

The heater control valve seems to be working - when the car is off the arm is pushed out; when the engine is running the little arm pulls in. Does this mean it's working?