AB-Oz

Has anyone with a right hand drive 964 fiddled the front demister vents so that the right hand side of the screen gets cleared, instead of the left hand side of the screen?

It sometimes rains here, and sometimes its cold (-2 this morn), and I'm getting sick of my side of the screen being fogged...

crg53

Maybe your servos are not working correctly. Mind you my car is LH drive, but it should be the same; the top slide on the HVAC unit should be all the way to the right and when I push the fan high speed/window button (right below the recirculation button), the window is clear in seconds.

Jim Howley

Yep definately sounds like the servo on that side is not working correctly. Mine was the same but for left hand side. Check out the guide on this page for instructions on how to have a go at repairing the problem yourself, just be careful when cleaning the connections in picture 19 as they are very fragile.

AB-Oz

thanks for the link Jim, I've removed the panel and checked the 2 temp servos (2+4) and both are working - well the arms on the servos move!

Still no cool air on the rhs, while the lhs blows fine. With the fan on, if I turn the temp from cold to about 24deg, the fan stops!? Is this because I tested with the engine cold?

I do need to check servo 5 now, see if it opens both sides of the vent...

AB-Oz

Well servo 5 works fine, opens and shuts the windscreen vent. I've taken the vent cover off and can see the flap openning and shutting, also there is one wide inlet which should then cover both sides of the screen, yet air only comes out of the lhs.

Fot cold air (up to about 24deg on the dial), the fan/blower on the rhs of the car (lhs when looking at it from the front) works then shuts off after the 24deg mark.

Is there a fan on the other side of the car that is not working? Is the lhs fan supposed to blow air to the rhs of the screen?

I will persevere with this, but I'm stumped at the moment...

Rocket Rob

The left and right fans should run at the same time. I suspect you had a faulty one. Does the LHS one have voltage on it?

DarrylH

Although it's completely counterintuitive, the two front fans can malfunction if the rear blower isn't working correctly. The usual symptom is that the front fans stop working if the temperature control is set to higher than the cabin temperature. Check that the rear blower comes on when heat is called for.

Troubleshooting the heating system is much easier if you have access to a Bosch "hammer" - it allows you to start and stop all the fans independently, as well as check the servos and some other stuff. Any chance anybody down that way has one?

AB-Oz

thanks for the tips, I'll move on to checking the rear blower and lhs fan next.

Not much chance of access to a hammer here, there's only 2 or 3 other 964's I'e seen on the streets, and they aren't on the forum.

AB-Oz

How do I check this Rob?

AB-Oz

well I've solved this temporarily, by covering the lhs vent holes with a strip of 100mp/h tape, so that the air is forced out of the vent holes on the rhs.

Still looking for help with lhs blower motor though...

Noisyone123

Hello AB-OZ, this is my first post on this site. I have an almost identical problem to yours everything on my heater system works fine except the drivers side demist.

My question is have you managed to sort the problem out yet apart from the temp. fix which I have also been considering ? (tape)

My hot/cold air servos (both sides) appear fine both fans appear to run the servo that sends the air from the cabin vents to the windscreen works but only sends air to the passenger side.

This is driving me nuts and nobody as yet seems to have had this problem before or if they have they are not telling us about it !

Noisyone123

Please Help !!!

tbennett017

Have you checked the mechanical servos that redirect the air? In this case you will want to check the two outer servos for function. Remove the plastic valance inside the front boot-lid and have a helper move the slider for the upper defrost back and forth while watching those servos. They should move in unison.

Noisyone123

I have checked all five of the servos and they all seem to be operating correctly. The only thing I noticed was the aircon pipes were fouling the passenger side servo arm (hot/cold air). I had to remove the two brackets that hold the aircon pipes in place to allow free movement of the arm. However, this has not cured the fault. The only time I get a small amount of air from the drivers side demist vents is if I turn the temp guage to max and blowers on full.

Whilst attempting to figure out this complicated heating system I started looking at the rear blower. In its plastic housing there is a small spring shaped resistor with a contact breaker on it (it looked pretty tired) could this cause the kind of problems I have described? Does anyone know what this part does? Its's just below the temp sensor.

Any help appreciated.

Kuchar

1. Out - CCU and radio
2. unscrew feet vent
3. Check out if flaps works corectly (mirror image)

1st picture feet

2nd picture windscreen

If flaps wasnt work correctly You have to adjust them. But it requires a great deal of work.