Hello
I replaced the compressor, condenser,and dryer on this truck. I used cheap eBay parts because the truck has 200k miles. The original compressor had a switch on the back that is held in with a snap ring. The new compressor has a threaded plug where the switch should go. The system is charged and cooling well. I haven't seen the compressor cycle though. Not sure which switch this is. I just taped it to the harness. It does have to be plugged in in order for the compressor to run. There is a switch on the dryer and one near the high side charging port. My question is, will this work as is or does the compressor need this switch. I would have to find one that is threaded, if that is possible. I ran the truck for over an hour and it cooled fine, just never heard or saw it cycle.
1998 Chevy K2500 5.7L
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Scv123
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Re: 1998 Chevy K2500 5.7L
Uhm- that would be the high pressure cut-out switch- that will shut down the compressor at 425 psi head pressure to avoid blowing the pressure relief valve at 500 psi. It is a normally closed switch, system will not run without it plugged in- it opens upon high pressure and closes again at about 250 or so..It is designed to be put in the hole that the aluminum plug is in. Remove plug from new unit, and transfer switch from old to new unit- saves the cost of the switch to the compressor supplier.
What you call a threaded plug is probably the brass high pressure relief valve- has a green piece of plastic inside usually- to keep dirt out of valve. The aluminum plug should be held in by the same snap ring that holds the switch in.
Switch on the accumulator/dryer is the evaporator freeze protection switch (low pressure cycling switch) opens at approx 22 psi, closes at 47 psi- the switch on the high side line is the recirc door switch, or can be used to turn on electric pusher cooling fan out front of condenser if installed on your model- Usually just 454 cu in engines.
By bypassing the HPCO switch, you risk blowing your charge out the high pressure relief valve if you ever experience extreme head pressures- as in no cooling fan(s) - or plugged air flow through condenser etc..
If compressor has no place for switch to go- then you have the wrong compressor for your model truck- some 6 cylinder GM trucks of that era did not use the switch on rear of compressor- and had a switch for HPCO elsewhere in the system. You may have bought the compressor meant for a six cylinder application if there is absolutely no switch port.
What you call a threaded plug is probably the brass high pressure relief valve- has a green piece of plastic inside usually- to keep dirt out of valve. The aluminum plug should be held in by the same snap ring that holds the switch in.
Switch on the accumulator/dryer is the evaporator freeze protection switch (low pressure cycling switch) opens at approx 22 psi, closes at 47 psi- the switch on the high side line is the recirc door switch, or can be used to turn on electric pusher cooling fan out front of condenser if installed on your model- Usually just 454 cu in engines.
By bypassing the HPCO switch, you risk blowing your charge out the high pressure relief valve if you ever experience extreme head pressures- as in no cooling fan(s) - or plugged air flow through condenser etc..
If compressor has no place for switch to go- then you have the wrong compressor for your model truck- some 6 cylinder GM trucks of that era did not use the switch on rear of compressor- and had a switch for HPCO elsewhere in the system. You may have bought the compressor meant for a six cylinder application if there is absolutely no switch port.
Re: 1998 Chevy K2500 5.7L
Thanks for the reply. The threaded plug isn't brass.
Just a plug with an o ring. The hole is too small for the switch which is held in with a snap ring.
Typical eBay, my year, make, model, and engine were listed as compatible.
I just want it to cycle. I didn't see or hear it cycle, but it didn't freeze up either. Maybe I'm looking for a problem that isn't there.
I understand the purpose of the hpco, but if I can make it through the summer, that would be good. This is a work truck and has high miles.
Just a plug with an o ring. The hole is too small for the switch which is held in with a snap ring.
Typical eBay, my year, make, model, and engine were listed as compatible.
I just want it to cycle. I didn't see or hear it cycle, but it didn't freeze up either. Maybe I'm looking for a problem that isn't there.
I understand the purpose of the hpco, but if I can make it through the summer, that would be good. This is a work truck and has high miles.
Re: 1998 Chevy K2500 5.7L
Cycling is dependent on heat load across evaporator- so to see it cycle, open hood, reduce blower motor speed to lowest speed and make sure it is on recirc air inside- wait about 10 minutes- it should cycle eventually.
Re: 1998 Chevy K2500 5.7L
Yes, thanks. I saw it cycle. The low side line did frost up, but that went away when I increased the fan speed.