Defroster problems

MixMasterK · 01-18-2004, 08:55 AM

Anyone ever have a problem with the defroster on an '86 944. The servo that should actuate the flap door to redirect the air is not moving. Is there something I should check first? Is something with the climate control unit bad? Also noticed the fan speed selector will not always come on except for in the highest position. Bad switch?

Kris

SoCal Driver · SoCal Driver's Garage

Fan speed is dependent on the ballast resistor working. This is on the outside of the air box under the hood. There are thermal overloads on it that need to be cleaned.

Would guess that something is disconnected to the vacuum valve for the flap.

ronin · 01-18-2004, 10:29 AM

as opposed to thermal overlords

don't forget to push your slider switch all the way to the top. you should then have air coming out of the defrost and side vents at full blast

MixMasterK · 01-18-2004, 01:42 PM

The slider switch only blocks off the air to the center vents. Inside and above them is another flap that is actuated by a servo. However this servo does not want to seem to move when the defroster button is engaged.

ronin · 01-18-2004, 02:02 PM

you still need to move the slider to the top. are you not getting any air out of the top at all, and is the defrost flap not moving any? is the footwell flap not closing either?

MixMasterK · 01-18-2004, 03:45 PM

Footwell flap/servo system works. It's the top servo/flap system that is not actuating at the same time. I know the center slider needs to be closed for the defrost to work, or rather aid in redirecting the airflow to the defrost chamber. However, since the second servo system is not moving, the air really doesn't go anywhere. No air out of defrost duct.

Kris

ronin · 01-18-2004, 04:28 PM

hmmmmm. and that damned unit isn't the easiest to work on either. it could be the defrost flap motor or the flap itself. first thing would be to check if the control motor (front driver's side of unit) is getting current and if the flap is binding or has come loose somehow. I don't see any relays that are assigned to the flap motor, so that's one less thing to worry about for now

Mark_944S2 · 01-18-2004, 05:56 PM

In the summer did the AC work OK? If not it could be the control unit in the dash (includes the sliders, and the switches).

Also I remember something about a clip that commonly fails on 944s? Connects one of the sliders to the unit? Can anyone enlighten us?

Mark

ronin · 01-18-2004, 06:09 PM

although the defrost function does switch-on the A/C for pulling moisture out of the air, it is independent of the function for the defrost flap. once the defrost button is depressed, the system switches to full heat regardless of the position of the sliders. also, the sliders are electric rheostat type connected to a solid-state system, so they don't clip to anything mechanical. Kris's best bet for now is to check the electrical connections to the motor and its connections to the flap and see where it goes from there

btw: too bad you sold the S2. but hey, now you can get a 951!

MixMasterK · 01-21-2004, 11:10 AM

Another thing to note is that with the defroster off, if I move the slider for the top side vents on the climate control, nothing happens with the flaps. In other words, if I slide it left or right, the flap system does not move. The lower selector does move the flaps for the lower part of the system.