'88 944 heat comes out of air vents constantly.

crossiono · 03-02-2001, 06:11 AM

Heat blows continously out the air vents even with the blower off and temp set on cool. Gets very hot. I close the vents but heat still comes out. Don't know where to begin to fix problem and hot weathers getting close.

todd951 · 03-02-2001, 06:31 AM

I had the same problem a while back in my 951. It was a bad heater control valve (the part that lets the engine coolant flow through the heat exchanger to heat up the vent air).

Harp · 03-02-2001, 07:26 AM

My car did same thing so I looked under hood. Right near my battery, mounted all by itself with nothing connected to it, is this strange black plastic cylinder mounted to a bracket. It is 3 inches in diameter and about 4 inches long. Absolutely nothing was connected to it, no wires or anything. There was one approx 3/16 inch diameter rubber coated black wire dangling loose near it which had a rubber 90 degree angle boot on it with a metal contact visible inside the boot. The only place it could connect to is a ½ inch long plastic protrusion/nub on the underside of the black cylinder (a little hard to spot it). My friends convinced me it “probably” wouldn’t hurt to just connect the wire up to the nub, since it did seem to mate properly, (although it used up ALL the slack in the wire). I shoved it on hard, and sure enough my heat now turns on and off at my command. I think the black cylinder receives info from the interior temperature sensor on the dashboard, and then somehow it sends a signal to control the heater control valve or something. I suspect that wire comes loose often when a new battery is installed. My car had a new battery put in last Sept.
Also the guy I just bought the car from took out a high-tech stereo system the day before I bought the car from him, he might have knocked it off.

914efi · 03-02-2001, 07:32 AM

there was an artilce in a recent excellence about a linkage that breaks on a heat control flap under the dash that causes the heat to stay on all of the time.

3sonfather · 03-02-2001, 07:47 AM

Harp, that black plastic cylinder by your battery should be your vacuum plenum which serves to compensate your vacuum system upon demand such as when your vacuum power booster is used during braking. It may be teed off for environmental control actuation on the newer models (86 on).
Scott

Harp · 03-02-2001, 08:01 AM

I have a newer model (1988) by the way.

lordgrommit · 03-02-2001, 06:34 PM

check the heat control arm
get under your dash upside down look to where the radio is if there is a metal rod hanging move it up till you see the clip that it;s suppost to clip into mine was broken but worked for two weeks till I got a new clip $1.50 from porsche.

ps bring the old clip with you it's really hard to see on the diagrams