94' 964 heat always on.

rching · 01-21-2006, 12:15 PM

When driving my 94' 964 C-4, The drivers side under dash gets hot like the heater is on. The heat is coming from the tube that drops down behind the footwell. Is there a heater valve that could be stuck open? This is just on the drivers side and I just noticed it. Haven't traced it further, thought someone may have some suggestions before I get down on my hands a knees. Thanks in advance.

planeguy67 · 01-22-2006, 10:39 AM

Wow, sounds just like the problem I was having on my 944. It's apparently a common problem with those, but I'm not sure if it applies to the 911's as well.

FWIW, if it's at all like the 944, the typical suspect is a little plastic connector that breaks and lets go of the control arm that shuts the heat flapper off. Without any control, the flapper valve opens dumping heat when not asked for. On the 944, the control arm and connector is under the dash, just inside of where the driver's knee would be, under a small black plastic cover.

Might be worth to take a quick look.

rching · 01-23-2006, 07:07 AM

Thanks, I'll look further into that. I noticed that the blower fan in the engine compartment was on, even tho' I didn't have the heat on. That's the next area I need to look into, thinking I may remove the fuse for that fan and see if the heat continues. If not, then I'll know what to look into next. Anyone ever have a fan that doesn't shut off? Some relay or defective heater/air cond. switch? Thanks all!

planeguy67 · 01-23-2006, 11:17 AM

Quote:

Originally posted by rching
Thanks, I'll look further into that. I noticed that the blower fan in the engine compartment was on, even tho' I didn't have the heat on.

If I understand the system correctly, and I may not, that engine blower fan comes on automatically when the engine temperature reaches a certain value. That hot waste air coming off the cylinders is used via a heat exchanger to provide warm air for the passenger compartment. That being said, that hot air is available ANYTIME either the engine electric blower fan or belt driven fan is operating and the engine is warm enough to heat the air, i.e., it does NOT matter if you have the heater on or off, the hot air is always available.

The heater valves in the dash, whether they be controlled by a flapper like in the 944 or whatever, are what determine whether or not that hot air reaches the inside of the car.

So, unless I'm totally screwed up, the engine blower has nothing to do with the heat always being on in the passenger compartment. True, if it weren't on while the engine is off, then there wouldn't be any hot air available for heating inside the car, but that doesn't mean the system is ok. IOW, you should be able to select cool air regardless of how hot the air coming off the engine is.

Make any sense??? (good, now explain it to me!!!)

rching · 01-23-2006, 12:20 PM

Thanks, I appreciate the time involved in explaining this to me. I'll add it to my mental data base and dig into it further!!! If it were the fall, I'd leave it for the winter months. but don't need the extra hear in the summer here in so cal!!!

Britwrench · 01-23-2006, 04:10 PM

The hose from the lower frame rail up to the heat intake has probably fallen off or is torn. Take the trim panel off and you should see the pipe.
There is always heat in the pipes as the valves are in the front, unlike the previous 911. The paper pipes tear easily, usually when an alarm or radio has just been installed..............

rching · 01-23-2006, 09:11 PM

Thanks, that's one of the next things I will check. It's only a matter of time before this pelican board helps me solve this problem.