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964 climate control unit switching the fan off

GT3 RS

GT3 RS

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Firstly many thanks to David for your kind help and advice at last weekends Silverstone Classic.

Hi I'm new here but not new to Porsche Cars as had many over the years, mostly new.
So having now ventured back in time to a 964 C4 Targa 1991 I knew I would be chasing some problems.
Now having done a lot of replacement and improvements over the past year the only problem I'm now left with is the CCU fan cutting out as soon as the temprture is turned up from zero, I managed to remove and send the CC unit to a company who said they could test it, but then said they couldn't ??

I've read the article on here saying replace the fan ballast resistor on the rear blower unit, however I wouldn't know if that will cure the fault, so thought I'd ask here first as David kindly suggested, anyone had the same fault and found what is needed to cure it please ?

Many thanks, Rob, Hove.
 
It's a fairly complicated system. Have you tested with a pst-2 or piwis? That would be my first point of call.
 
The CCU has been known to be the root of many head scratching problems. I know mine is playing up as I too get intermittent function and the rear blower is no longer working (motor is brand new and all runs perfectly with a ditrect 12v feed and new fuse). However, having a functioning CCU isn't on the critical list (warm cabin not highest priority). Only caveat being the oil cooler fan does receive a signal from the CCU. If your oil cooler fan comes on when it should then all good.

For all CCU fixes and repairs the guru is Tore Bergvill. All CCU questions answered on his own site or many threads on rennlist. The rear ballast resistor replacmement is a factory recall item and your nearest OPC should fit this for free.
 
I had similar symptoms with mine many years ago which I eventually traced to a poor power connection at the rear blower unit which had allowed the cable to become disconnected. I seem to remember it's quite difficult to get at and I discovered it when attempting a test similar to the one described above by mcgc0. This blower is powered by a 25A fuse in the box on the left side of the engine bay and if this blows it will cause similar symptoms. I hope this helps, please keep us posted as to the solution when you find it. Paul.
 
Agree with Paul, the rear blower cable is a real pain to access. There are some that have removed the blower completely and instead use the (carbon fibre) bypass pipe. Some weight saving to be had. The 25A fuse was increased to 30A following a Porsche tech bulletin. Make sure you have the 30A fuse installed.
 
Many thanks to all for taking the time to offer help and advice, Mid Sx did an engine out and new clutch earlier this year, they found a melted fuse holder which they replaced but nothing was said as to its cause.
I'm fairly sure the CCU was working fine until I recently removed it to do a dash retrim. I have read an article saying a similar fault was caused by the blower fan ballast resistor (I'm not familiar with that) has anyone replaced the fan ballast resistor curing the same fault as mine please ?

But as mcgc advises have this checked/changed if it hasn't already been done.
I will speak with Mid Sx again to get the story straight, not sure what Tim is saying Ps-2 etc but it has been on the computer diagnostic twice at Mid Sx and made mention of the main blower but not what to do.
I will respond to Dave for his notes and email Tore Berville

kind regards, Rob.
 
Many thanks to all for taking the time to offer help and advice, Mid Sx did an engine out and new clutch earlier this year, they found a melted fuse holder which they replaced but nothing was said as to its cause.
I'm fairly sure the CCU was working fine until I recently removed it to do a dash retrim. I have read an article saying a similar fault was caused by the blower fan ballast resistor (I'm not familiar with that) has anyone replaced the fan ballast resistor curing the same fault as mine please ?

But as mcgc advises have this checked/changed if it hasn't already been done.
I will speak with Mid Sx again to get the story straight, not sure what Tim is saying Ps-2 etc but it has been on the computer diagnostic twice at Mid Sx and made mention of the main blower but not what to do.
I will respond to Dave for his notes and email Tore Berville

kind regards, Rob.
 
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