My 1985 300D w/ 150K miles...Climate Control System went out. For about 2 days, sometimes it would come on and other times when I restarted the engine, nothing. No air circulates or blows at all on any setting. The couple times in those 2 days it did come on, heat and cool worked strong and perfectly. Now nothing will come on at all.

I checked the clutch on the compressor and when the car starts, the clutch spins and then stops.

I read about replacing blower motor brushes, could this be it? Seems too easy. Would this cause the clutch not to engage?

How do I diagnose the source of the problem...certain steps to take in order?

Thanks.

It could be the ignition switch. My car has this problem but there's an easy way to work around it. I just make sure that when the key is in the "on" position (when the engine runs) the mark on the key hole cover lines up with the mark on the outside, which involves simply turning the key slightly towards the "off" position. Give that a try.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

yes check the electrical portion of the ignition switch, keep in mind the 85's have a klima relay located next to the fuse box under the hood. ina small square plastic box. you can dissassemble it and check the solder joints on the circuit board, another easy way is to smell it. if it smells burnt i would start there
how about the pushbuttons????

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81 300d non turbo (seized eng)
83 300d turbo 180k
85 300d turbo trap car 331k (runs like a clock)
94 e420 70k
98 320 60k

The ignition switch is indeed a common cause of this problem. The switch is inexpensive and easy to replace.

Good luck,