RX7320 AC is short cycling

T

tjohnson11

New member
My RX7320 is about 5 years old (only 270 hours). This summer the AC has started "short cycling"... for about 6 seconds the light and the compressor go on, and the air is cold. Then the light goes out, compressor goes off for about 8 seconds... and then starts all over. All the filters and coils are completely clean. Good air flow, and the low side freon is exactly at spec. I don't have a way to check the high side.
Is the compressor going bad, or could it be the high or low side sensors?? Any ideas would be helpful.
 
Doing air conditioning work "over the phone" doesn't usually work out too well. "low side freon is exactly to spec". Now what does that mean? There is only one gauge, so it's probably on a charging can. How accurate can we expect that be?

Short cycling. What can the problem be? COULD be low on charge, but not necessarily. Could be a pressure switch problem. If there is a high and a low pressure switch or a binary switch involved the high side could be breaking the circuit due to higher pressure than the switch wants to see. Without a high side gauge who knows if that's involved or not. It could be a thermostat issue. After all, that's the component that's in there to stop/start the compressor based on desired temperature in the evaporator.

A five year old system could easily be slightly low on charge, even if you don't think so. My guess is some refrigerant has been added at some point in time, maybe just recently. Yes/no? How much would that be?
 
Fedup said:
Doing air conditioning work "over the phone" doesn't usually work out too well. "low side freon is exactly to spec". Now what does that mean? There is only one gauge, so it's probably on a charging can. How accurate can we expect that be?

Short cycling. What can the problem be? COULD be low on charge, but not necessarily. Could be a pressure switch problem. If there is a high and a low pressure switch or a binary switch involved the high side could be breaking the circuit due to higher pressure than the switch wants to see. Without a high side gauge who knows if that's involved or not. It could be a thermostat issue. After all, that's the component that's in there to stop/start the compressor based on desired temperature in the evaporator.

A five year old system could easily be slightly low on charge, even if you don't think so. My guess is some refrigerant has been added at some point in time, maybe just recently. Yes/no? How much would that be?
Click to expand...
Has freon been added to the system using a can and not a gauge manifold with a vacuum pump connected on it? Systems are factory charged, after a 30lb vacuum is applied to remove any traces of air. When adding freon from the can from the auto parts store, the line does not have an vacuum applied to it before you put it on the low pressure side. So, every time you use one of the recharging cans, you are injecting air into your system. After a while, that air adds up.

My 09 F250 was that way. I kept adding cans of freon. The system put out luke warm air, yet it showed, on the low pressure side, fully charged. It wasn't until I took the truck in for service, they threw a vacuum on the system and extracted all of the old freon, oil, moisture and air and then put a full charge of fresh freon and oil on it, did it work perfectly fine. It is still working fine.
 
The point (as I see it) is this. Homeowner servicing of A/C systems has its limitations. If the system only needs a little freon added, and what you have on hand is a parts house recharge devise with a single pressure gauge and a low side adapter fitting, you can get lucky. That will work, provided that's ALL the system needs. How does "one" know if that's the case? "One" doesn't. So "one" grabs a can of "adda charge" dumps it in, and looky there. Cold air in the cab again, everybody's happy, and we move on. Sometimes it works out that way. Sometimes it doesn't.

Proper servicing has a few requirements. To begin with, the individual doing said servicing needs to understand how the system works, what components are involved, (and hopefully where they are on the machine) and TWO functioning gauges. Without that everything is guesswork.
 
I guess that's what I'm asking... where to start?? Is there any easy way to test the low and high sensors?? Any way to test the compressor?? I'm somewhat mechanically inclined, but have never worked on any AC systems.
 
Start with a set of gauges. You need to know the static pressure first. That gives you an idea of the charge status. Then start the system and see what the gauges tell you. What you do next is based on that. Without gauges you have nothing to work with.
 
Ok... time to embarrass myself. The actual condenser coils are sandwiched between the engine radiator and the transmission radiator, with a guard over them. I clean that area several times a year, and must have just gotten it clean enough each time to make it through the season. This time it was completely packed with dirt. Took the two guards off and used a hose to completely clean it. Now the AC works awesome (even in 92F heat).

Thanks for all the responses and help. Enjoy the rest of the summer!!
 
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