1996 850 AC air vent control problem

442Classic · Post by **442Classic** » 09 Jul 2008, 02:11

Well recently I have noticed that after driving for about 40 minutes my car begins to warm up a little and the routing of the cool air changes by itself. One minute it will be blowing from the dash vents then it slows to a trickle but the fan speed stays constant. I can hear the fan working but it seems to be not making it to the dash vents anymore. It does this in either the auto or manual settings. If I shut off the car for about 20 minutes, everything is fine again. Can the floor/ defroster damper motor be failing? Can it be replaced?

chuckcintron · Post by **chuckcintron** » 09 Jul 2008, 06:31

Is the delivered air coming out warmer, or is it simply being rerouted from the top vents to the floor vents? If the latter, then (since it sounds like you've got electronic control) either the head unit is screwy or the damper motor is shot.

Both can be replaced, but I wish I could tell you how to test them before going down that route....maybe VADIS has a procedure...not sure.

-Chuck

Post by **Maxbaby** » 09 Jul 2008, 12:17

If your system is working fine for the first 40 minutes or so, and then it's trying to change (elevate) the temperature, I'm thinking it's something to do with the temperature sending unit. The vents will adjust to add heat when the system wants to increase cabin temperature. I would start by getting some compressed air and blowing out the little sensor. I can't remember (someone will correct me soon enough) whether in your model it's located above your entry handle above your head or in the light console above your rear view mirror, but one of the two places. You should also have the codes read.

442Classic · Post by **442Classic** » 09 Jul 2008, 14:34

The air stays nice and cool, just the volume coming out the vents is reduced. It is like the vents close them selves off & the fan speed stays the same.

Post by **Maxbaby** » 09 Jul 2008, 17:14

442Classic wrote:... It is like the vents close them selves off & the fan speed stays the same.

That sounds like the damper motor controlling the fresh air / recirculation damper, which still makes me think temperature sensor issue. If the damper motor itself were broken, I don't think it would be adjusting itself. It would just be sitting wherever it died. I still suggest blowing compressed air into the temperature sensors to clean things out. Then go and get the codes read.

442Classic · Post by **442Classic** » 23 Jul 2008, 22:04

Well I cleaned the temperature sensors, they were covered in dust & dirt, with compressed air and put it back together. But on occasion it still seems to close off the air coming from the blower motor. Is there a damper motor that can close off the blower motor all together? Could the blower motor be the issue? It is a new unit (about 6 mnths old) from FCP. Should I replace the temp sensors as I have several parts cars in a local yard?