I've hooked a multimeter up to the power connecting to the clutch. It is getting 10.49 volts. Is that enough to power the compressor / activate the clutch, or do I need a solid 12 volts?

My compressor clutch only activates sometimes, and I'm trying to figure out why. Here's what I've done so far:

1. Jumped switches at receiver dryer.

2. Replaced "ice cube" relays.

3. Replaced climate control unit.

4. Had AC system charged.

I did all this before arriving at the AC clutch and now can see it not spinning when the car is started. When it does engage, I hear that "click" when I turn the ignition. The I have cold air, which is nice to have in 100 degree heat here in Memphis.

So, if the compressor is not getting the power it needs, then WHERE THE HECK AM I LOSING POWER????

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1984 300D

The problem could be the evaporator temp switch. It is supposed to open at around 36 degrees to prevent the evaporator from freezing. However, the switch can malfunction and open at a much higher temp. The typical scenario is that the a/c will work well for a few minutes and then quit for an extended period.

Let me start by admitting I did something dumb. I realized that the compressor was getting full power after I turned the motor on. If I just turn the key to the point where it engages the electrical system, the multimeter shows it only getting 10.49 volts. After starting, multimeter jumps to 12.

That's not the stupid part. With the electrical leads back on the compressor, I started the car. The clutch didn't engage. I touched the front of the clutch with a pair of needlenose pliers to see if it was magnetic. It was. The clutch engages via electro-magnet. So the magnet worked, but still no clutch engage. Then I pushed the front of the clutch toward the compressor slightly and boom: clutch engages. With the clutch gently moving in and out, I sprayed the clutch gently with engine cleaner degreaser. Now the clucth will engage. All that work and turns out the clutch was just "sticky". Wow.

I admit it was stupid, but I would have never figured it out otherwise....

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1984 300D

Larry, I'm not sure what a feeler gauge or an air gap is. How can the air gap be adjusted?

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1984 300D