hi Porscher's,

i've got the following pboblem with my 964.

times to times the heather of my 964 blows cold air... i can not adjust the temperature... when i start to drive faster (+160 km/h) the system blows really HOT air ... read very hot air ...

Now i checked the flapmotor's and discovered that 2 of them doesn't work.the freshair and the footflapmotor ...
I have set the valves manually ... but that doesn't seems to be the problem ... because the system keeps blowing HOT air in...

The controller in the dash is checked and works fine.

Is there another/reason that the hot air keeps coming inside the car ???


greets
Dirkie

 

gonna try this one first ans see what's happens ...

http://www.porsche964.co.uk/technical/servos.htm

 

That procedure is certainly a STELLAR reference to use. Roly did a good/thorough job in covering the subject of servos, CC unit, etc.

I especially like the photos that show the location of each servo.

Good luck, my vote is for the CC unit, being that the trouble is inconsistent.

 

ok ... so far .. not so good ... the servo's went out ... 1 was doing a little bit crazy ... cleaned the contacts ... works great now outside the car with 12 volt on it ... so i'am pretty sure that the servo's are ok!!
Unfortunally ... the hot air keeps blowing in .... the servo for the mixingflaps right side does nothing in the car...

Any suggestions for the next step now ...???

Greets
Dirk

 

I don't have anything helpful to add, but I do have a similar problem. I can get hot air only in the center dash vent (both sliders all the way to the left). The windshield and foot vents never get warm when I slide the sliders to the right. Anyone know the cure for that?

Thanks,
BJB

 

see the link in the second post of this topic ... there is probably your answer

Clear that one of the servo's is jammed.

Greets
Dirk

 

Dear Bjb,
Try selecting defrost and seeing how much air is heading to the windshield. Should be maximum.
The air to the windshield and the air to the footwells are controlled by two different servo motor valves.
The air to the vents is controlled by differential air pressure. I suspect that your defrost valve is stuck this is why I suggest giving it a kick by selecting defrost.
Ciao,
Adrian
964C4

 

Hi Dirk,

I had this a while back...over a year and Randall and I had some fun diagnosing the fault. One tip for you is that it is possible to physically remove and connect servos to positions that appear not to work, my point is that you need to be very sure its not the servos before replacing the CCU, or anything else. I think I removed a "working" servo i.e. one that moved when it was supposed to and plugged it into the lead for a non working servo. In my case the servo moved which confirmed the CCU was ok i.e. supplying voltage and sensing position ok, and the servo needed cleaned and regreasing. Obviously this only tests the CCU's ability to drive the servos and not any of its other functions. But still an easy way of testing servos.

Taj.

 

Adrian,

I took the car for a ride today (weather's near 50 fahrenheit and roads are dry for a change) and I discovered that the air is warm from the center vent, passenger side vent, passenger side footwell vent and from the passenger side of the defroster. The air is cool on all the driver side outlets. The air comes out where it is directed to (both the sliders work and pushing the defrost button works also). I think I have seen the answer to this "one-sided heat" problem somewhere, so I will look around. I have your book on order and that might help as well. Of course if you know which servo I should be looking at I would appreciate your input.

Thanks,
BJB

 

Dear BJB,
The problem is I do not know where you are. Do you have a LHD or RHD.
If you have a LHD the failure is with the left mixing chamber servo valve. You cannot miss this one it is the one with the arm on it that disappears into where the left blower fan is located.
If you have a RHD then it will be the right mixing chamber valve.
The servo will be stuck in the full cold position. You can pop the arm off the servo and move it manually to the full hot position or any position inbetween.
Ciao,
Adrian
964C4

PS: Left and right are given from the drivers position facing forward.

 

Gentlemen,


next episode in the "heater" story,

Got out all the servo's ... they are working ok !! Now i put them back in ... they work 3 times and then they give up ... very very strange ...
When i pull them out again ... try them on a 12volt source ... pins 4&5 ... they work again ... put them back in ... again 3 times ...


Dirk

 

Dear Dirk,
No really strange at all. The motors in these serovs are toy model motors made in Hong Kong. When you remove them and test them they are not under any load. When you reinstall them they are under load and fail.
I recommend you at least try and open one up and check it out internally. A clean up can help for a short time.
Or pull one out test it but this time under load. The load on these servos is quite high. They work hard.
Ciao,
Adrian
964C4

 

ok Adrian, many tnx for your reply's.

I'am gonna order 2 new servo's today.
I now somebody who's selling them second hand but i'am not gonna take the risk...

One last question, is it normal that the front blower in the 0 position on the control unit keeps blowing very little ???

Happy New Year

To be continued...


Regards
Dirk

 

Dear Dirk,
Good luck with the first lot on the servos. To answer your second question, yes it is. The fan are required to run at 0. This speed is also variable. Some people often ask what the speed input to the control unit is for. One reason is for the fan speed at 0. The fan speed can also be varied by the temperature sensor installed (no you cannot see it or get it out it is molded) in the fan blower amplifier.
The other item which uses driving speed is the fresh air servo. The faster you drive the servo will start to close.
Ciao,
Adrian
964C4

 

Adrian,

I am in the US, so LHD, and it must be the left mixing chamber servo. Thanks for the help!

BJB