I used to have the HEAT ALL THE TIME feature until I fixed that broken plastic clip that is so common. Cheapest repair yet I think.

The car has been running well for years but all of a sudden, no heat in the cabin, only outside temp air. It happened right after a trip north where the car went on some bumpy roads. Maybe something got shaken up. Last time I went there my odometer gear broke.

Anyway, here is what I've checked so far.
1) Fuse ok
2) Blower works
3) flaps top and bottom work
4) temp **** does cause flap lever under dash to move. clip is in place. So it looks like the control module is fine.
5) Vacuum lines seem fine. Have not been touched.

So, what is the next step. Looks like I'm not getting any warm fluid through the heater core or the core is misbehaving some other way. Anything else I can check before this gets more serious? I've read that flushing the cooling system might help? Is it worth swapping the control module?

Before this problem developed, the temp indicator on the car would climb near into the red when idling in warm temps. A quick rev of the engine would get the temps down again. I'm wondering if this is all related?

Thanks in advance for any advice.

 

Take it out. Who needs heat? Kitty cats and women, that's who!



I had a problem similar to this about two weeks ago. The "door" that simply shuts/opens that directs heat into or out from the cabin was not opening fully and when I would move the switch to 100% heat it would not open the door all of the way. Even if the clip is in place, I would inspect to see that the door is working properly- it may just be not opening/closing correctly.

 

Heater control valve?

 

I need heat too! Don't forget I live in Canada. The A/C I've managed without, but when it's +35C mid summer, you get cooked without that too!

Today it's a low of -4C at night ... brrr.

I will double-check the door, but the flap arm is moving a pretty good distance so I would expect at least some heat from that.

Maybe it's this control valve. I'll read up on that. I was thinking maybe the thermostat due to the odd overheating problem. Almost like something gets stuck until I rev the engine and get the fluids moving.

 

+1 on the Heater Control Valve, given the other causes you've eliminated. This is a common failure on a 20+ year old P-car. Do a search on this part name here and look at Clarks Garage site for advice and steps to replace. Part is readily available from several stores on the web - not expensive. I'd suggest replacing this valve before the control module.

 

It should fail open.

 

Check if the hoses that are coming in to the car at the passenger footwell are hot or not.
Remove the rod from the clip and see if that makes a difference.
Temperature sensor?
http://www.clarks-garage.com/shop-manual/ts-10.htm

Went the cooling system
http://www.clarks-garage.com/shop-manual/cool-02.htm

 

I second venting the cooling system.
An air bubble will prevent coolant from circulating.

 

check the level of the coolant, and see if the vacuum line to the HCV is still connected and start car pull off this vacuum line and see if it is getting vacuum in various selector positions

 

Thanks for all the tips, folks.

Regarding the Heater control valve failing open ... does this mean if it has failed I should be getting heat NOT a lack of it? I've been reading that this system is supposed to fail in heat on mode to prevent the driver from freezing in a car with a hot engine

I went on a 1 hr trip last night and oddly enough the heat would come on for a minute or so, but not very hot, just warm, then it would go back to outside ambient temps. Does this give a clue to anything?

- I'll check the pipes entering the cabin next and pull the clip to see if the heat stays on.

Stay tuned.

 

I have been having the same problem since I replaced my heater valve and I am 100% sure it is because I didn't do a good enough job bleeding the cooling system afterwards. When I replaced the valve it was summertime so I didn't really care, but now it would be nice! I have been driving the car fairly hard in that timespan so I was expecting it to "burp" out any air that was in there but i haven't had any luck it seems.

I also have a crappy Stant radiator cap which is rated at 16 psi, and I have read that the stock ones are 22 psi. I don't know if that would have anything to do with it. Might help me from blowing headgaskets at least!

 

how did you properly bleed the cooling system to fix your problem? I just did a waterpump job on my 944t and now I dont have heat and been trying to figure out what it might be..

 

This will be quicker than me trying to explain it:

http://www.clarks-garage.com/pdf-manual/cool-02.pdf

You may have other issues, but try that first.

My problem was actually different. I found out later that the solenoid valve which controls the vacuum supply to the heater valve was stuck open, holding the heater valve closed. See these threads for other ideas:

https://rennlist.com/forums/944-turb...-heat-lol.html

https://rennlist.com/forums/944-turb...nts-fixed.html

 

thanks! ill read up and try some more things before i post again on my issue

 

Sorry to threadjack.. But the damper under the drivers side footwell is not moving when i turn the temperature **** from cold to hot. What does this indicate? Assuming im testing it properly... I dont see the rod or anything moving down there at all and it looks like little white plastic clips are in tact