A/C compressore cycling

[adale]

Should my compressor cycle? I converted my '93 Navajo over to R134a and the compressor does not cycle and I can't remember if it should. Thanks!

 

[cjbarron5]

i dont think they started the automatic cycleing untill late 95 or 96 i think

 

[JTX]

Is it on defrost when its doing it?

 

[Glacier991]

A/C compressor cycling rate is a function of charge state, cabin temperature and ambient temperature. In an individual event, if the pressure falls below a certain amount (around 25 PSI on the low side) a low side cutout switch turns off the clutch and the compressor stops. In the "off position" the high side bleeds into the low side, increasing its pressure. At around 45 psi or so the switch kicks back in and the compressor starts again. How often this happens depends on the first things I mentioned.

This was not some "engineered" event, it is just how the system has always worked on a "fixed orifice" system. The refrigerant used is secondary. You may in fact have a bad low pressure cutout switch, or a significant overcharge.

When you converted, did you evacuate and put a measured amount of r-134a in the system? Remember the amount of r-134 should be about 80-90% of the previous amount of r-12. Put some gauges on it. Watch the low side pressures as it operates.

Otherwise it may likely be a bad switch.

HTH.

 

[adale]

I did put gauges on it and I also evacuated it when I did the conversion. My low side pressure goes lower than 45 psi but the compressor always runs. I also have a slight leak that has developed but I dye'd the system when I converted but I still can find the damn thing!!! Oh well it took almost 3 months of 90 degree heat for the system to show a low charge. How can I find out what the pressure set point is for the switch? Thanks!

 

[Glacier991]

I would be helpful to know your operating pressures. Low side, High side, cabin temp and ambient external temp and vent temps. Short of having a controlled environment I am not sure how one might check the switch operation on a system that never got to 25 psi on the low side. You know another possibility is that your compressor is getting weak.... worn out... that's where the pressures would help in diagnosing.