‘97 Pathfidner A/c

[A1218]

Do the a/c compressors on these vehicles cycle? I notice that whenever I happen to idle with the A/c on a very hot day it would once and a while cut off, but then it comes back on several seconds later.

I’ve previously posted about this. About 7 years ago the original compressor blew (just started smoking while idling) and I replaced aftermarket. Same thing happened with aftermarket or I believe the clutch locked up on aftermarket.

I replaced that one two years ago. Now this one the clutch didn’t lock up or anything but I hear it click off then on again several seconds later like I stated in the beginning of post. I don’t believe I’m low on Freon and it blows cold. Takes a few minutes to get going when extremely hot but other than that it’s pretty fine.

[mdmellott]

There is an a/c high pressure sensor switch on the compressor that will turn it off when the refrigerant pressure gets too high because it's running hot. It will then turn back on when the pressure drops, which usually happens in short order after the compressor is turned off by the same switch.

[A1218]

So I’m assuming this is normal operation?

[VStar650CL]

On a '97 it's definitely supposed to cycle. The ECM controls the compressor based on input from the "Dual Pressure Switch" which indicates both high or low refrigerant pressure. In normal operation, when the evap gets too cold the expansion valve (TXV) closes and pressure rises on the high side of the system. That causes the DP switch to go overpressure and cycle the compressor off. Then the TXV warms up and opens, the pressure falls and closes the DP switch, then the cycle repeats. That's why the system is classified as a "cycling clutch" type. When that type of system doesn't cycle very much or at all, it usually means low refrigerant.

[mdmellott]

It's normal but if it is happening continuously, like off and on several times within a minute or three, there may be too much normal refrigerant pressure to begin with. I have found those pressure gauges often sold with a refill can of R-134 to be not very accurate. The last time I added any to my '02 was years ago and the disposable gauge read normal, right in the green band. However, there was actually too much pressure which caused my compressor to cycle on and off too many times in too short a period of time. I relieved a bit of pressure to the lower end of the acceptable pressure limit band on the gauge and then the compressor was well behaved after that.

[VStar650CL]

It's normal but if it is happening continuously, like off and on several times within a minute or three, there may be too much normal refrigerant pressure to begin with.

Yep, overpressure will make them cycle like crazy. If you're DIYing refrigerant, the best way to make sure you get it right is a cheap vacuum pump and a postal scale. Weighing the cans works fine. That's all an A/C machine does when charging, it weighs the tank.

[A1218]

I generally don’t hear it cycle unless under those certain conditions. Idling for a bit when it’s very hot and humid out. Other than that the compressor runs continuously.

I didn’t charge it by can recently. When I changed the compressor two years back I had it vacuumed and recharged professionally. I did however decide to check a few days ago with one of those gauges from the can and it was right in the center of the green section.

Does the radiator fan and clutch affect the a/compressor in terms of overheating? I’m still running the original fan clutch.

[mdmellott]

Does the radiator fan and clutch affect the a/compressor in terms of overheating? I’m still running the original fan clutch.

No relation. Not sure they are even driven by the same belt but that wouldn't matter either, even if they are.

[VStar650CL]

Md is right, condenser airflow is a secondary factor to when and whether the system cycles. The fans can't "overcool" the condenser and cause or prevent cycling. On the other hand, evap airflow is a primary factor. The system pressure is a complex balance between the compressor, TXV, and the thermal load through the evap. But this sounds like a case of, "If it ain't broke, don't fix it." If it works well but cycles a little less than some other systems, trying to diag why will be complicated and maybe fruitless. If it starts working less well at some point, that will be a different story.