95' K2500 w/350CI
When I turn on the a/c the compressor cycles for a few seconds then shuts
off for a few and back on again for a few etc. I originally thought I was
low on R-134 and bought a refill can that came with a guage. The guage
toggles between low (less than 25psi and filled (25-45 psi) depending if the
compressor is on or off (again it cycles every few seconds). Sounds to me
like a compressor problem, but could this be because I'm low on R-134?
The Input and output lines to the evaporator (inside by heater core) should be
the same temperature when the system is full. An
inbalance would indicate low charge.
This is easy enough to check under the hood.
The low side pressure will increase when the compressor shuts off, this is
normal. The low pressure cutoff switch will kick off the clutch at 25psi.
So, she's hitting 25psi, shutting off, the pressure increases then it kicks
back on again.
You need to read the pressures at cruising RPM (in your case likely 2,000
RPM) with the compressor clutch jumped directly to the battery to keep it
sucking from the refill can. When you get to 27-30 psi @ 2k RPM, unjump the
clutch and it'll stay on, and give you low side pressures around 45psi.
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