Hi,
I turned on my air con today for the first time in a long time. The problem is is that nothing happened. Its an '85 126 280SEL.

I checked the fuse (#11), and found that it was quite hot. I also checked the voltage at the clutch, and it was 0v. I then shorted it to +12v very briefly, and measured the voltage again and it read +12v. After leaving it like that for a while, I noticed that the pipe running to the condensor was getting hot, but the other pipe wasnt changing in temp.

As soon as I switched the ac off and then on again, the voltage at the clutch read 0v again.

Is this a saftey device that if the refigerant is too low the system won't operate?

I also remember that before when I used to run the ac the rpm of the engine used to drop quite a bit, but now there is no change in the engine speed.

The compressor is a merc (nippon denso)original system.

Any help would be greatly appreciated!!

Peter.