964George

OK, so used the car Saturday and discovered there was no heat, actually there was nothing at all!!!
No hiss of air from motors, no power to the CCU, nothing, nada, zilch...

When I got home I popped the bonnet and took a look at the fuses?
And what do you know fuse 1 has blown.

Replaced the fuse and it seemed OK, so I started the motor and tried the blowers, nothing?
Checked the fuse again, blown!

So I got to use my new toy for the 1st time, T-ODB Scantool purchased from ToreB

And there I have it, two CCU errors...

13 - Right mixing chamber temprature sensor
31 - Left mixing flap motor



I've found the offending parts on PET and the best prices I can find on the net are from Rose Passion.

96465990100 Temprature sensor mixing chamber repair kit £153
96462490300 Electric motor footwell flap with lever /Left £302

Does anyone know of any alternative parts from other German marques that can be used?

Using the Rennlist search I found this outfit who refurb the Servos...

http://translate.google.com/translat...le_fuer_964993

But I had no joy looking for the temprature sensor...
Can these be cleaned up and made to work again?

Any ideas or details on a cheap supplier appreciated

ToreB

Thanks for the reference George40.
A blown fuse 1 most often means a stalled fan motor. There's two of these in the air box in the trunk, and the bearings wear, causing the fan cage to crash into the fan housing. There's lots of threads here on the forum on how to change these, here's one of them: https://rennlist.com/forums/964-foru...ront-dash.html
The HVAC servos can only be bought new at the Porsche dealers. No other car makes use these. Partisan Autoteile sell excellent refurbished servos as exchanged units.

The CCU store OBD fault codes from time to time, often by hiccups in the electrical system or other causes. Try to clear the codes and maneuver all CCU controls to exercise the things. Then, see if the codes reappear.
The mixer chamber sensors are made as a part of the front HVAC wiring loom. Based on the schematics, it is probably a normal 12,5kOhm NTC thermistor. You could try to change or clean the sensor without removing the complete wiring loom.
Here's pictures if the sensor.
Cheers,
Tore

fuch

I have a feeling I might be after the same parts as you George as I blew fuse 1 last week & using it this w/end I smelt a electrical burning smell with the fans on...bugger!!

964George

Hi Tore

Thanks for the reply.
I'll try clearing the codes and adjusting all the controls.
Fans were working fine before this issue, not even squealing!
Hoping I don't need to replace the fans as that is not going to be fun.

Here's the new temp sensor, looks like it's a splice in piece.

http://www.rosepassion.com/en/cat/po...-sensor/P47666

Cheers

George

964George

Finally had time to look at this...

Codes cleared and all controls moved around.
With the fan speed set to 0 everything works fine, I can adjust the temp and I here the fans coming on and going off.
Checked for CCU errors and it has error 13 again so guess I'll try cleaning the sensor before splashing out on a new one.

Codes cleared again but this time if I adjust the fan speed to 2 then it blows the fuse
Checked for CCU errors again and nothing listed

Anyone got had this issue?

ToreB

Front fan problems causing the fuse to blow will never generate an error code in the CCU. Keep us updated on your work on cleaning/changing the mixer chamber sensor.
Cheers,
Tore

boxsey911

Could George unplug each fan separately to see which one blows the fuse and then run with the offending one unplugged until he can get a new fan? If so, where are the connectors?

I'm watching this with interest because mine has the tell tale squealing coming from a front fan which I guess is going to fail in the future.

ToreB

I haven't been in there myself, but guess you either have to disconnect at the fan motor terminals (difficult) or unplug the motor wire in question on the fan Final Stage connector harness. These are Brown/Grey for right fan, and Brown/red for the left fan. Final Stage connector is (5) in the below picture.
Cheers,
Tore

ras62

Once the fans/motors are removed it is possible to change the bearings. Not easy but possible. Also the right side fan motor (not the fan itself) is the same as found on a Benz 190! About £50 or less on ebay.
This thread shows bearing change
https://rennlist.com/forums/964-foru...rt-number.html
The temp sensor I think is a simple thermocouple, so long as it is clean and the two metals brazed together at the end it should work and produce a small mV signal.

ToreB

The mixing chamber temperature sensor is a NTC for sure, not a thermocouple sensor. However, I am unsure of the NTC value, I expect it to be a normal 12,5kOhm type based on the car schematics information (12,5k @20 degC) and on the other sensors used in the HVAC system.
Cheers,
Tore

alexjc4

lol, my HVAC is all over the shop and always has been, thankfully I still get hot and cold air out of the vents but the blower motors are noisy on anything above 1. Set to anything other than full cold or full hot the temperature of the air seems to swing wildly and in a way apparently unrelated to the settings on the CCU. Hay ho it's all part of the fun

LM964

Hopefully the attached Bulletin may be useful to some. Codes and potential causes/rectification included. Backed up with Tore's nounce this should help...

Harry Apps

"nounce"? Is that text speak?

964George

Thanks for the PDF, should prove useful.

STUARTQ

I have an issue with heating too and haven't had the time to figure out what the problem is.

Mine is an intermittent problem, so it's either on or off and whilst driving along will come on for few seconds, then it's off again. I can put up without heat on a personal level, but it's a pain when the windows are misting up.