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coralpolyp 01-17-2010 01:22 PM

86 635 CSI heater problem

I'm new to this forum and hoping for some assistance with my 86 635 CSI.

I have a problem with the heater, in regulating the cabin temperature.

I replaced the heater valve with a used item today since I assumed this was faulty. I still have problems but the heater valve is regulating, just way out of calibration. I'll explain:

I started the car and set the dial to 21C. After a time the cabin reached 26C and was still rising, and the supply air was an incredible 51C.

I turned the dial down to absolute minimum (less than 16C) and the valve was closing, since the supply air temperature dropped, but only to 30C, so still actually heating the cabin.

If I turn the dial up just a fraction, the supply air temperature rises up to 39C, despite the dial setting of only 16C.

So, the valve is regulating, but way out of calibration with the setting on the temperature dial. The cabin is roasting, so I need some advice on this, and if possible an explanation of how the system controls so I can start fault finding.

I also need to know if the 2 pin plug on the heater valve has to be a specific way round. It can be fitted either way so I assume it makes no difference.

I'm pretty competent at electrical testing - any advice would be gratefully received.

Thanks in advance.

mnepitjr 01-26-2010 11:57 PM

I hink you should buy the kit and rebuild the heater control valve. I had the same problem on my 88 635 and rebuilding the valve fixed it.

coralpolyp 01-28-2010 10:57 AM

Thanks - I've already ordered the kit and hope to get the valve rebuilt shortly. If that doesn't resolve it I'm back to square one again.

coralpolyp 02-15-2010 01:33 PM

I rebuilt the valve. Still the same problem.

I can see the valve regulating but the temperature is way too high in the cabin - the control temperature dial seems out of sync with the actual temp.

Anyone have any other ideas?

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