drohalloran

I also posted this on 944online.com...

Ok, I turn to you, experts of the 944/1, in the hopes that you can solve an age old mystery that has limited the use of my '83 944 to winter only:

I cannot get the heat to turn off.

And that's not say that I don't enjoy the full bore barrage of lava-temperature heat directed almost perfectly into my face on a scorching August day, but I would greatly appreciate any help in getting this off.

Now to this I have replaced the HCV, so that doesn't seem to be the issue. Added to the mystery is that the car consistently runs hot (to the 3/4 mark and often beyond) although I have checked the PSI of each cylinder and I don't believe the headgasket is blown. I've also replaced both the water pump and thermostat several times in the hopes to alleviate this, also to no avail.

As well, the car does seem to have a vacuum leak somewhere because the idle can rise and fall (something I know is indicative of a vacuum leak).

Besides that, the car runs and operates fine, and has for the many years I've owned it. It has 70,000 original miles and has been garage kept for most of it's life.

With all that said, I really hope someone can point me in the right direction. Thanks so much!

MooreBoost

check your vacuum lines and the blue and black vacuum check valve next to the brake booster. try replacing your fan switch on the radiator. i would do a cooling system pressure check to see if you have a head gasket leak

Dimitri_944

On the passenger side of the engine compartment there is a vacuum line that goes down into a little rubber grommet on the fire wall that contains a couple fittings. i believe this goes to the heater core. but my heat used to be stuck on and i reconnected that line it it worked.

I think it goes from the heater control valve to the heater core. I'm 300 miles from my car so i can look but ill try and find a picture.

F40LM

FWIW I had this happen with my 83. If the heat selector arm moves too freely it has broken on the back. I was told the heat system was engineered to auto go to full heat in case of failure. There is a spring system back there that while cool it was a PITA to repair.

Dimitri_944

here it is, Vacuum lines 4 and 5 come through the fire wall down behind the cam tower its really hard to get to but i did it with out removing anything,[IMG][/IMG]

AlphaOmegaPower

Glad you posted this. Same on my 83.

AlphaOmegaPower

I know your pain -_-

lee101315

Even after all this, if you still can't stop it, remove the heater valve and install a water valve from the plumbing supply at Home Depot.

Dimitri_944

No problem just doing my part sense i have used my fair share of knowledge from this site

MooreBoost

that looks like a later heater. still have the same vacuum lines

drohalloran

I can't thank you guys enough, it's been really great looking through all this feedback! I'm going to take a look tomorrow and begin the (potentially ugly) job of resolving this!

I've found that everything relating back to this heater has been a major hassle, but I'm determined to fix this issue

odurandina

before the next time you start the car,

how bout you start by removing the fuse to the heater fan.

divil

Before you go hunting for vacuum issues - do you know whether the heater control valve is being operated correctly by the controls? If it's opening/closing as you turn the temp ****, then it's working.

If so, look at this: http://www.clarks-garage.com/shop-manual/hvac-01.htm

Scroll down to the pic labeled "HVAC UNIT LEFT SIDE"

See those pushrods connected to items 3 and 4? Have you checked those on your car? One of these is held in by a fragile plastic clip which breaks all the time, resulting in full heat(as someone mentioned it's designed to fail to full heat so you don't freeze)

This seems to be the most common cause of having full heat stuck on.

If it's the clip as I'm guessing, this won't fix it. You'll get heat coming through anyway!

Are you sure it's not just air in the system that's causing the high temps? It's very tedious to bleed the air out after doing any coolant system work. Since you've done lots of that kind of work I'd start with making sure it's bled. Shout if you need more details on how to do that.

Jfrahm

The early cars do not have the plastic clip problem.

If you have replaced the cable operated hot water valve, have you verified that it is closing with the control? Is it still possibly leaking water? I had a bad valve that looked OK and operated OK but passed enough water to the heater core to heat up the cockpit a lot. It could be your valve is not closing all the way or is defective.

You can try something like this:

http://www.summitracing.com/parts/FSS-84706

to eliminate the flow of water, at least for testing.

-Joel.

F40LM

Lol