QuestionHi and thanks for your time.
I am working on a 98 Chevy Surburban 4x4 5.7l. I have not been using the truck alot the last few months and the other day when i went to use it the A/C compressor would cycle on and off while the truck was warming up and once warm wold not turn on at all. I read through your pervious posts and figured out i may be low freon so i jumped the low pressure switch on the accumulator and the compressor came on and I took a pressure reading using on of those recharge kits from the auto parts stores. The reading was right on the line between low and normal so i added a little bit of freon to bump it up into the middle of the normal area. Disconnected the jump and reconnected the wires to the low pressure switch and the compressor shut off. Pulled it back off and put the jumper back on and the compressor came back on. The air in the truck is cold front and rear.(can take exact temp reading if needed). I am thinking that i may have to replace the low pressure switch and if i do is this something i can do? Will it let all the freon out of the system by changing it out? Thanks for the help.
Joe
AnswerJoseph,
One thing that I am finding this year (every year it is a new most popular problem) is that the vehicle's engine temperature is playing a large role in what you are describing.
Your PCM (powertrain control module) is the brain for your vehicle. Everything goes through it. In order for it to allow your compressor to come on, certain conditions must be met. First, you were correct is jumping to checking your charge. That is one requirement. Without the proper charge, your compressor will continue to cycle. If you charged it correctly it should have continued to stay running. BUT another requirement that the PCM must be happy with is that your engine coolant temperature must be below 250 degrees fahrenheit. If it is higher than this, it will disengage the A/C so that the radiator can cool more efficiently without fighting against the heat created by the condensor (directly in front of the radiator)
You telling me that it cycles at first and then nothing when the truck warms up leads me to believe that this is the next check you should make. Has the engine temp gauge been reading higher than normal lately? If so, I recommend youchange your thermostat (coolant thermostat not A/C thermostat) and possible have the radiator flushed if it has never been done or the coolant looks "rusty"
I would not be willing to say that your low pressure switch is bad, because it is doing exactly as it is supposed to from your description ("the A/C compressor would cycle on and off while the truck was warming up") When there was a low charge, that is what it does.
So I would first check your coolant temp/radiator fluid. I believe this is where you will find your problem. If not, let me know and I will be happy to continue working with you through the electrical portion.
Thank you for your question, I hope I was of some assistance. If so, please remember to rate this answer. If I can do anything further either now in this process or in the future, please do not hesitate to ask. Thank you again and good luck in everything.
