heater problem

[andrew holland]

Hello all,
I wonder if anyone has come across this problem:
heater fan works fine on all 4 settings(speeds) but only if the temperature knob is turned to the coldest setting. As soon as I try to turn up the temp the fan will switch off . All wires are corectly connected to thre heater box on the engine . I suspect a fault with the heater head unit ?
Anyone with an answer ?. I would be very grateful considering the weather is getting cooler by the day !
Andrew .
993 c4 (96)88000miles .

 

[hanhams81]

Andrew,
If you live in the South call up "Cool It", Martinstown, Dorchester.(01305 889843) speak with Alan or Noel, both Porsche freaks. They sorted my 993 heating/aircon at reasonable cost.
Hanhams81

 

[Steve Humphreys]

Hi Andrew

I fully support what Maurice recommends---take the car to a specialist not an OPC and if they connect the Porsche 2 diagnostic unit they can use this to control al of the servos--to see if there is a fault there as well as identify any problems witht he CCU---after you have done this you may wish to consider the following.

I am trying to sort out a number of heating problems on my 964--Eric Kessel from one of the 964 forums has posted this link at the bottom of my message with photos of the CCU--his links works through removing the CCU to replace one of the switches.

http://thekessels.net/car-stuff.htm

From what I know to date--try looking into the receiving area for the internal air--vent on the RH side of the unit--on my 964 this was full of fluff, etc.--I cleared this out but still no result--you may be luckier. My view is that this could well be a problem for you--if this is the case---with an external inspection then follow Eric's process and when you remoce the ribbon wiring you will be able to see clearly if there is any debris in the channel. When you have removed the CCU you will see a fan on the back of the CCU that draws air through the vent at the front and across a sensor

I am not sure how aware you are of the heating--the system is effectively controlled by 5 servos that drive the circulation of the air--these can be seen by removing the black plastic strip over the bulkhead---this also covers the final stage amplifier that fits between the fuel tank and the bulkhead--the CCU controls these 5 servos and therfore the flow of the air into the cabin.

Hope this is helpful

Steve

 

[Dave Wilkinson]

Andrew,

I may be way off base here but I believe there is a lot of common ground between the 993 and the 964 so I'll make a suggestion.

You haven't mentioned if your rear blower is running. From my 964 experience, when you turn the temperature knob off the blue dot the rear blower cuts in, initially on slow speed, to force air through the heat exchangers to provide warm/hot air up to the blowers behind the dash. If the rear blower fails to start the CCU will cut off the dash blowers since there is no warm/hot air to boost.

If the rear blower is not running the most common cause is a blown fuse in the engine compartment electrical panel but can also be a faulty relay (in the same place). A blown fuse (30A) can often mean the bearings are worn in the blower motor causing it to draw too much current.

Hope this helps. Apologies if it's a load of b0110cks!!

Regards

Dave

 

[andrew holland]

Thanks to you all for your replies ..
I know that the little fan in the control unit works - had it checked last year since the climate control knob( temperature knob) didnt seem to be able to maintain a constant temp - i would set the temp to a certain temp setting and need to adjust it ( upwards ) to keep the cabin warm - sometimes it would need to be turned to max to keep the cabin warm.Will check the rear blowers...
Am taking the car up to 9m for them to have a look .
Was hoping for a quick fix [&o]

will report back .....
Andrew

 

[tomwinton]

Slightly off topic Andrew - but I do seem to have the problem you had, where I have to continually adjust the CC temperature dial upwards to keep the cabin warm... I've taken the fan unit apart and cleaned/lubricated it - it "seems" to work fine... but the problem persists. Curious to know if replacing the fan fixed your problem - and if your fan was totally dead, or still generally spinning?

ta

TOm

 

[andrew holland]

Tom
the problem is still there despite the fan apparently working fine . I suspect it is part of the bigger problem. Am still trying to find time to take the car into the local independent to give them a go at finding the problem. In the meantime I am slowly freezing myself in the mornings !
andrew

 

[tomwinton]

Andrew

THanks for the feedback - think I'll pass on wasting £100 on a new fan unit then... would be interested to hear what your indie says - I too am waiting to find the time to take mine in.... will keep you posted.

Ta

TOm