MarkGolfWritten by PCGB member Mark Sloane, his account on a DIY repair of his climate control unit. Climate Control Unit Repair. For a long time I have been aware that my defrost slider did not direct air towards the windscreen. This wasn’t usually an issue as I try to only drive my car in the summer/dry weather. Lockdown boredom generated time to investigate further and seek a solution. The obvious place to start was with the servo (located behind the fuel tank). There are 5 servos in total. The defrost servo is the first on the left. After supplying 12 volts to the servo I was able to confirm the servo works and the arm moves to open and close the flap. I then made some wires to connect the warm air servo connector to feed the defrost servo. I did this to see if adjusting the warm air signal from the ccu would open and close the defrost flap. It did. This also confirmed that the servo was not the issue and that the CCU was doing its job correctly for the warm air adjuster. The lazy option at this stage would be to disconnect the defrost servo in the open position which would allow air to the windscreen all the time. I’m not one for doing half a job so I soldiered on, keen to find the root cause. Further investigation also revealed that the servo for the footwell and the warm air mixer on the right were also not working. A reconditioned CCU can cost up to £600 so I was now at a point where I was very keen to fix it. I turned my attention to the outputs from the CCU unit. I wanted to see if the CCU was providing the necessary voltage to drive each servo. Some quick continuity checks taught me which pins on the CCU connectors fed each servo. Using a multimeter I could see whether the correct voltage was going to each servo. As I slid the adjuster the footwell or the defrost I could see the output shot to overload. Further reading online suggested the power overload reading was due to the power op-amps being unable to maintain the required voltage to activate the servo. I found some replacement op-amps online for £4 each so I thought I might as well replace all 4 to ensure I don’t have to repeat the job again in the near future. The components you need are Siemens TCA2465. (marked as IC9,10,11&12 on the pcb)I soldered in the new op-amps without any issue and as soon as I plugged the CCU back into the connectors and turned on the ignition I could hear the servos moving to their correct locations. So, after 8 years of procrastination, here is how long it took me to fix the issue:- 1 hour to confirm servo all servos operating correctly using remote 12volt supply where necessary.2 hours – checking wiring and continuity.2 hours - online research (looking for wiring diagrams and other useful hints)1 hour - soldering in new op-amps.5 minutes to pat myself on the back and put the plastic cover back over the servos! Next job – Replace the recirculation button now that everyone in the club has seen a picture of how shabby looking it is! Thanks to Mark for this and as in the picture, my CCU is the same, what is with the upside down icons?! What is the reason for this? A picture of Marks beautiful 964
mcgc0Yeah, my CCU was flakey to start with and now no longer functions. A Bergville revival is on my list but tbh, it not working hasn't been a showstopper for me - never needed to warm up the interior or demist the screen. However, I know it has other complicated functions which other engine components depend on - oil cooler temp signal inputs for low/high fan speed (not just the ballast resistor for this) and the rear blower fan etc.. Oil temp/cooling for me is excellent and never exceeds 10 o'clock pos even after tracking. Still, one day I'll get round to getting the CCU done and I'll be keeping an eye on this thread in the meantime.
iangray100 Interesting, my brain works in a different way ...if its not working I get the electronics fixed while someone in the world is able to do this work to a high standard and at a reasonable cost and it also comes with 5yrs warranty (the cost of the electronics from Porsche are silly money and their supply (recon or new) wont least for ever) .
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