Heater Broke

[Marky Boy]

Hi all.

Posting this here in the 944 to get the most coverage and its a generic problem i think. This is for my 968.

My heater is blowing cold all the time. Had a look at the heater valve and when i turn the heater control nowt happens to it. So am assuming this is jammed closed and not letting hot air into the heater matrix. If this is the case is it likely to be the heater valve itself, i.e diaphram, or a vacuum leak.

I pulled the center controls the other night to remove the clock but i dont think it was enough to dislodge anything. Does the vac run from this direct to the heater control valve??

Any one concur or having any extra knowledge or ideas. Please let me know your thoughts

 

[Guest]

I assume you have enought coolent circulating the system. Low levels will can cause that, with other obvious problems. Just a thought. Other than that, posibly a valve stuck closed?

 

[Diver944]

It does sound a little coincidental that you had the control unit out recently. Maybe one of the plugs became a bit loose on the back of it, also check all your fuses are still ok. Failing that I would remove the glovebox liner (5 screws) and watch if the control levers move up and down as you turn the control dials. If they do then it looks like the controller is okay.

Another thing to check is all your small vacuum lines in the engine bay are still connected. If it's the same as the 944 there should be a vacuum reservoir in front of the steering wheel (a black plastic tube about 4" by 2") that you can follow the lines from. The heater matrix is under a thin plastic cover just at the bottom of the windscreen, you can gently lift this up and see if everything is still connected

Edited I forgot that I had a similar problem a few years ago. My heater dial gave out no heat but if I pressed the rapid demist button for full heat, I got lots of it. This was the sensor under that thin plastic sheet. It detects the outside air temp and fails thinking it's already very hot, so no matter what temp you dial in, it defaults to cold because it thinks you roasting in there. It's a £20 part if that is your problem

 

[944Turbo]

On my 86 lux the servo motor that moves the hot cold flap had siezed (beside the glovebox). Once this was repaired (stripped, motor run when taken out, cleaned put back together) the other parts worked again (the vacuum operated coolant tap). Mine was stuck on Hot so coolant tap was staying open.
Another problem (though IIRC it gives heat if you hit the defrost button) is with the temperature sensors 2 inside one outside - its usually the outside one that fails but sorry don't know where any are located.
Edited to say I see Paul edited his reply to add this bit!

Tony