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Over the last couple days I've had the AC pumps seize up in both our CX840s, one was about four years old the other is older. Anyway when I buy pumps they always seem to have oil in the crankcase but I've never added oil into the system except when I was experimenting with Redtek R12A which didn't seem to work so well and got real expensive so I returned to R134A.

Most of my AC work on trucks and tractors works out great and I don't have much troubles with those systems but these combines have been a bit of a nightmare with leakage. The main culprit was the low pressure line from the cab to the compressor, both of them started leaking like they were perforated, got new ones from New Holland and they both leaked at the cab end (and the fittings were oriented wrong :mad:), I cut them off and re crimped them so they seem better but I still have leakage somewhere. The system sure works nice when it's going but I don't want to be recharging them every twenty to fifty hours. Does anybody know if an R12 detector works for R134A?

Anyway this oil situation I would like to figure out, there is never much evidence of oil when I dismantle systems but I'm sure there should be oil circulating in the system. Does it pressurize the crank case of the compressor and use oil from there? Any way to know when to add or how much oil is actually in the system? This has always bothered me. The oil is a PAG oil or something I believe, correct?

Thanks.
 

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I would just use detergent in water and a spray bottle to find the leaks. The oil used is generally PAG 100 weight. Systems with large long lines and large condensors need a good helping of lube. Systems with slow leaks slowly get low on lube.

I like to clamp a high temperature sensor on the pressure line to the condensor to save the compressor by interrupting the ground to the clutch. It's getting hard to obtain that part, that was common on 70's era equipment, but its much more dependable than high and low pressure switches.
 
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