1983 c30 A/C Compressor Clutch

biggfrank99 · May 20, 2026

I have replaced my ac compressor evaporator core dryer and condensor. System calls for 10oz of Pag oil. 2 oz in dryer 2 oz in condensor and 6 in compressor. Done. Pulled a vacuum and no leaks. Charged ac to 45 lbs on ac gauge. Starts blowing cold and when I put the vehicle on the highway the clutch burns up. This has happened 3 times.

Finkaire · May 20, 2026

Sounds like high pressure, start with a lower charge. I would lean more to compressor failure than the clutch, contamination? Check inside the discharge hose from the compressor for contamination

biggfrank99 · May 20, 2026

Three brand new compressors with all new parts. Hoses flushed with ac flush and blown out with dry compressed air each time. On each compressor the paint was burned off the clutch of the compressor each time. It was a crusty white looking color.

Bextreme04 · May 20, 2026

biggfrank99 said:
Three brand new compressors with all new parts. Hoses flushed with ac flush and blown out with dry compressed air each time. On each compressor the paint was burned off the clutch of the compressor each time. It was a crusty white looking color.

Make sure everything has a good ground. The clutch is powered through the low pressure switch and then grounds through a bunch of mounting points to the engine and then back to the battery. Make sure you have a good clean connection from the compressor to the engine and a good clean ground wire from the engine to the frame of the truck and from the frame to the ground terminal on the battery.

biggfrank99 · May 20, 2026

Thanks a lot sir. I will definitely do that before I set it on fire

Bextreme04 · May 20, 2026

Also, filling to 45psi on the low side is crazy to me. How much is it taking to do that? You should be filling to 2/3 the recommended fill amount of R-12 and adjust from there.

Burning up to me sounds like a power/ground issue to the clutch. The clutch will usually engage hard enough that it will physically bend a piston before it starts slipping.

Bextreme04 · May 20, 2026

Unplug the clutch plug and test voltage across the two pins while it should be engaged. Then check voltage(voltage drop) from the ground side of the clutch connector to the battery negative and the same from the positive clutch pin to the battery positive. You should have 12.4+ between the two connector pins and a very low number from each pin to the battery terminal. If you have a number over ~1.5V from ground to the battery negative, you have a very bad ground connection and need to fix that.

biggfrank99 · May 20, 2026

Thanks a lot. I will try that as well.

biggfrank99 · May 20, 2026

Bextreme04 said:
Also, filling to 45psi on the low side is crazy to me. How much is it taking to do that? You should be filling to 2/3 the recommended fill amount of R-12 and adjust from there.

Burning up to me sounds like a power/ground issue to the clutch. The clutch will usually engage hard enough that it will physically bend a piston before it starts slipping.

biggfrank99 · May 20, 2026

I was going by the book.

Sad Sack · May 20, 2026

biggfrank99 said:
I have replaced my ac compressor evaporator core dryer and condensor. System calls for 10oz of Pag oil. 2 oz in dryer 2 oz in condensor and 6 in compressor. Done. Pulled a vacuum and no leaks. Charged ac to 45 lbs on ac gauge. Starts blowing cold and when I put the vehicle on the highway the clutch burns up. This has happened 3 times.

Good reading:

A burned clutch is a symptom of another problem - MACS

#burnedcompressorclutch, #compressor, #clutch

macsmobileairclimate.org

Bextreme04 · May 20, 2026

biggfrank99 said:
I was going by the book.

That's not how that works. You could have twice the acceptable charge for your system and still have it reading 45PSI.

You filled it while running and AC on... right? I will usually pull a vacuum for 45-60 minutes, then check for leaks, then let it suck in most of a 12oz can, then start the engine and turn on AC. Once the AC is on, it will suck in the rest of the first can. Factory charge calls for ~48 ounces. You want ~80% of the original charge when converting to 134, so that would be just a bit more than 3- 12oz cans. I would put the 3 cans in and then check vent temps and slowly add some of a 4th can until you get the temps you want.

biggfrank99 · May 20, 2026

i charged it with 28 ounces of ac pro Freon. No additives. 10 ounces of pag 150 with the ac on and running. I was getting 40 degree temps idling and cruising around town. I got on the freeway and the clutch burns up.

Bextreme04 · May 20, 2026

biggfrank99 said:
i charged it with 28 ounces of ac pro Freon. No additives. 10 ounces of pag 150 with the ac on and running. I was getting 40 degree temps idling and cruising around town. I got on the freeway and the clutch burns up.

That's pretty low. What was the high side pressure at? You replaced the orifice tube when you did the conversion? My high pressure port is AFTER the condenser. If yours is also, you could have a clogged condenser causing this and it wouldn't show up on the gauge. Mine reads well under the max low side pressure even with a full charge.

Bextreme04 · May 20, 2026

I would still guess it is electrical though. What compressor do you have? R4 or A6?

1983 c30 A/C Compressor Clutch

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