What's up with my A/C compressor/cutch?
 

Today I changed all 4 belts and installed a new(used) blower motor on my 1982 300D turbo. This may or may not have anything to do with what I am seeing.

After completing the belt change, I started up the car and went to look at the belts. Belts all looked good, but I noticed the A/C clutch on the front of the compressor would engage and spin for a few seconds, then disengage and remain stopped for a few seconds only to engage and disengage repeatedly. I have the climate control set to defrost and temperature at the coldest setting.

Unfortunately, I don't know if this engage-disengage process was happening before the belt change, but it doesn't look right to me.

I took a video that shows what I am seeing. You can see the clutch disengage at 5 seconds and re-engage at 20 seconds.
A/C clutch engaging and disengaging - YouTube

~Shannon

Sounds normal to me. The compressor does not constantly run when you are using the A/C, and yours sounds just about right. If my hearing is correct, the clutch engaged for about 16 seconds. Below is a service step listed on a company web page that does A/C work. Only time I would be concerned is if the ac puts out weak cold air or none at all. Then you might want to have it checked for the proper pressure.

We verify tha the car air conditioner clutch engages and turns the compressor when the auto air conditioning system is running. We also verify the cycle times also to be sure that it's not cycling frequently (indicating low freon)

On a 1982 300D, the compressor normally runs constantly when an a/c mode is selected. It is possible, however, that the vehicle has been retrofitted with a binary pressure switch which could cause the compressor to cycle.

The temperature control is inoperative in the Defrost mode. Defrost should provide 100% heat and 100% a/c. (All a/c modes provide 100% a/c; except in Defrost, temp is controlled via the heater.)

Thank you for the heads up on this model.

Short-cycling is generally indicative of a refrigerant shortage.

X2, Low freon = low pressure. You may try temporairly jumping the connector at the pressure sensor on the drier.

X3, Low freon.

What the heck, X4, low freon

Can you explain the manner in which low refrigerant causes power to the compressor clutch to be interrupted, after the compressor is engaged?

Thanks for the suggestions. I will check on the refrigerant.

~Shannon