A/C charged but not working?

[Number21]

I have a '00 Silverado 5.3L. Last season, the A/C worked fantastic. This year...nothing. I assumed it was out of refrigerant, but, my gauges say it is still full. For some reason the compressor keeps cycling on and off - roughly 1 second on and 10 seconds off, over and over. The coolant lines under the hood get slightly warm and slightly cold, but nowhere near where they should be.

 

Anybody know why it would cycle on and off like this? I know how to charge it, but I haven't got the slightest idea what to check here...

[richard wysong]

what is the low side pressure when it cycles? Sounds like you just have a low charge. Are you using "real" gauges or the 1 on the freon can? Depending on ambient temp low side should be around 30 with the compressor running, static pressures are meaningless

Edited April 6, 2023 by richard wysong

[Robertabf]

Once you confirm the correct pressure - it may be the low pressure switch needing replacement.  I think it is an easy replacement, but I am a bit shaky on AC stuff.

 

I believe you can bypass the switch to test before replacement.

[richard wysong]

Low pressure switch may be adjustable, Screw between electric connectors but  you should probably evacuate and recharge th system with the correct WEIGHT of freon before changing any adjustments

[kickass audio]

like previously said it usually means you have a problem with low or overcharge on the refrigerant. Grab a cheap set of the gauges from harbor freight and check your low and high pressures with the temperature outside. Also depending on your ambient temp outside if it's really cold you won't need the compressor to run 100% so it will cause it to flip the clutch on and off. You can try to set the thermostat on the dash to full cold and full defrost which usually forces the compressor to run all the time. You also might have an issue where the pressure switch is failing (usually doesn't happen too often) or the TXV is failing and causing the pressure to go really high on the high side and it protects itself by command the clutch to disengage.

 

Also before you just slammed refrigerant in the system did you look for a leak anywhere? Don't make the mistake my dad did where he would buy 2 massive canisters of R134a and eventually blew the compressor from a constant leak and never putting any oil in the system or fixing the leak and pulling a vacuum to remove the moisture in the system.

[Pete Hernandez]

for future reference post the pressure (low/high)and your ambient temperature so we can help you diagnose your problem.

 

Like most said depending on your ambient temp, your pressures will vary. But you can bypass your low pressure switch usually located on the receiver dryer by unplugging it and jumping it at the connector. If the compressor stays running, what are the pressures? 

Too high?  Is your radiator fan working properly? Are the condensor fins plugged? Is the compressor releasing metal and plugged the inside or condensor and or orifice tube?

 

Too Low? Low ambient temp? Low on freon? 

 

Are the pressures equal (high and low) when the the compressor is running?  bad compressor

 

Normal pressure replace low pressure switch and or high pressure switch.
 

Edited April 10, 2023 by Pete Hernandez
I forgot to add something