Grunert R12 Fridge Compressor

[Bermuda Forte]

Gents, could I ask for some troubleshooting help?

The system worked well last season however, after completing some extensive Perkins motor work last month, the compressor fittings got loose. I added a 14 oz can of 134A and thought I was back in business. I only run at idle speed as I’m worried about high rpm. Cooling seemed fine. In any case, now I have observed a compressor noise. Sounds like marbles. Any ideas?

[Bowdrie]

Originally Posted by Bermuda Forte

the compressor fittings got loose.

"Fittings" as in plural?
Both fittings loose?
If unbeknownst to you all the refrigerant had leaked out and you fired-up the compressor, the compressor can suck-in a bunch of air.
That would compromise the system no matter how much refrigerant you subsequently added, (the air won't condense, it drives-up the pressure and heat).
Compressor noises are not a good sign.
Either the ball/socket joints for the swash plate/pistons, or externally the ball bearing unit that supports the clutch/shaft.
Lack of oil or overheating the most likely cause(s).

[Bermuda Forte]

Thanks for the reply

Specifically, the high side fitting was found loose and my non-scientific test by depressing the Shraeder valve clued me in that there was not much there.

Update: after a day, I restarted the system and ran at 1200 rpm for 45 mins. No noise and lots of cooling.

[Bowdrie]

Good, you dodged a big curve ball by not having the suction side come loose.
Edit; Do make sure the system has a proper charge, they depend upon that to insure adequate low side pressure and oil return to the compressor.

[Bermuda Forte]

Update just now. A day later I’m running fine for about 20 mins, frost on expansion valve and inlet pipe to holding plates. Part of the holding plate is cooled to 25F. Noise from the compressor again. I shut it off.