A/C cycling-recharge question

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Randy Whistler

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This is probably a dumb question, but - it's summertime in Kansas and hot. When the A/C is running on MAX(inside air), the compressor cycles on/off but does seem to cool after driving for a bit. My other vehicle(not GM) does not follow that cycle unless it's low on Freon. If the other vehicle is running on MAX cool, the compressor stays on without cycling.

According to my gauges, I hear the compressor cycle, and it seems to be running about 26psi, with the needle right on the line between low and filled. Once it cycles, the pressure goes up, of course. Sadly, I don't know which cycle is which - is it compressing when the gauges show low, and not when high, or the other way around?

So the question is - do GM's cycle always, MAX or not? I don't want to overcharge but don't want to overtax the system either.

As always, thanks!
 

swathdiver

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This is probably a dumb question, but - it's summertime in Kansas and hot. When the A/C is running on MAX(inside air), the compressor cycles on/off but does seem to cool after driving for a bit. My other vehicle(not GM) does not follow that cycle unless it's low on Freon. If the other vehicle is running on MAX cool, the compressor stays on without cycling.

According to my gauges, I hear the compressor cycle, and it seems to be running about 26psi, with the needle right on the line between low and filled. Once it cycles, the pressure goes up, of course. Sadly, I don't know which cycle is which - is it compressing when the gauges show low, and not when high, or the other way around?

So the question is - do GM's cycle always, MAX or not? I don't want to overcharge but don't want to overtax the system either.

As always, thanks!

I think you're low on freon Randy. If the outside temp is in the mid 80s or higher your low side pressure should be at least in the 40s.

@91RS
 

OR VietVet

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I am with @swathdiver on this one. Sounds like is low on refrigerant and likely have a seepage leak problem. There are many ways to search for the leak. Spray soapy water on all exposed fittings and around the compressor and look for bubbles. Use a sniffer that will act like a geiger counter when it smells something, they are not that expensive. If is just seepage you need to go very slowly with that sniffer and always hang around the low part of the fitting as refrigerant is heavier than air and will sink as it comes out. I am old enough I have used the open flame check and looked for the flame to turn green, indicating a leak. Be careful of course. You can use dye as well when you charge and then look with a black light for the leak where the dye comes out. I am not a fan of dye and if you use it and find a leak, I would recover all refrigerant, fix the leak, flush out the system, replace the accumulator and orifice, add oil as needed and charge with fresh refrigerant after evacuation of the system.

By the way, The cycling of the system depends on how hard it is working and how full the charge is. I lived in Missouri and did a lot of a/c work there. It is hot and it is humid and the a/c system is working hard in that climate. The a/c works harder in 90 degree weather and 90% humidity than an a/c system that is working in 105 degrees temp with very low humidity. Make sure your fan clutch is in tip top shape: https://www.rockauto.com/en/moreinfo.php?pk=668589&cc=1361551&jsn=2300

and make sure your radiator and condenser are very clean at the fins for air flow across them. I take the top plate off and expose the front and back of the radiator and the condenser and then use a long wand air nozzle to blow them out.
 
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