A/C Switch on the Accumulator
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A/C Switch on the Accumulator
I can get the compressor to "click" on only if I by-pass the switch on the accumulator. Do I need to replace the switch? And if so, can it be removed without losing refrigerant? I know I am low on my refrigerant charge, but shouldn't I hear at least one "click" from the compressor before the switch cuts it off? Or will simply filling up the charge without removing the switch make the compressor finally click on. By the way, this is an R12 system.
Race Director
Joined: Aug 2000
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From: HONOLULU HAWAII
Re: A/C Switch on the Accumulator (virtue4u)
virtue4u,
I don't know the answer, however I'm interested in what others have to say.
I'll be interested in knowing how this works myself.....I just switched from R-12 to R-134. Since then my compressor continues to click on (idle rpm drops), click off (idle rpm increases)...this happens every 45 seconds or so....I'm sure it's not supposed to cycle that many times in such a short period of time. Could it be a faulty switch?....Can this be changed or adjusted by me?.... :seeya Cappy
I don't know the answer, however I'm interested in what others have to say.
I'll be interested in knowing how this works myself.....I just switched from R-12 to R-134. Since then my compressor continues to click on (idle rpm drops), click off (idle rpm increases)...this happens every 45 seconds or so....I'm sure it's not supposed to cycle that many times in such a short period of time. Could it be a faulty switch?....Can this be changed or adjusted by me?.... :seeya Cappy
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Re: A/C Switch on the Accumulator (8T1-7T9 BIONIC VETTE)
Dear Bionic Vette,
I know the answer to your problem. The reason your compressor keeps switching on and off is because it is low on refrigerant. A switch designed to keep the compressor from ruining itself clicks the compressor OFF when it is low on refrigerant. Since you already converted over to 134a, all you need to do is charge it up again by buying a can of refrigerant. The bigger question for you is where did your refrigerant go? IF your leak is bad, you need to find the leak and correct it.
My problem (I think) is electrical or maybe I am so low on refrigerant that my compressor won't even go on (but I doubt that I wouldn't at least hear one click); however, I don't want to waste a can of expensive R12 trying to find out the problem. I need someone to help.
I know the answer to your problem. The reason your compressor keeps switching on and off is because it is low on refrigerant. A switch designed to keep the compressor from ruining itself clicks the compressor OFF when it is low on refrigerant. Since you already converted over to 134a, all you need to do is charge it up again by buying a can of refrigerant. The bigger question for you is where did your refrigerant go? IF your leak is bad, you need to find the leak and correct it.
My problem (I think) is electrical or maybe I am so low on refrigerant that my compressor won't even go on (but I doubt that I wouldn't at least hear one click); however, I don't want to waste a can of expensive R12 trying to find out the problem. I need someone to help.
Melting Slicks
Joined: Oct 2000
Posts: 2,143
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From: Englewood FL
Re: A/C Switch on the Accumulator (virtue4u)
Try pulling the connector from the accumlator switch and jumping across
it. The compressor should start and run. Hook up a set of gauges
to the AC lines. If the low side pressure is below 30 pounds with
the compressor running, the system is low on refrigerant.
As someone else said, the switch is activated by pressure. It is designed
to keep the compressor from starting if the pressure is low.
If the pressure is low, would leave the connector jumped as freon is added
to keep the compressor running.
it. The compressor should start and run. Hook up a set of gauges
to the AC lines. If the low side pressure is below 30 pounds with
the compressor running, the system is low on refrigerant.
As someone else said, the switch is activated by pressure. It is designed
to keep the compressor from starting if the pressure is low.
If the pressure is low, would leave the connector jumped as freon is added
to keep the compressor running.
Racer
Joined: Feb 2001
Posts: 318
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From: Morrisdale Pa
Re: A/C Switch on the Accumulator (mark79,80)
I just charged the A/C in my 75 and it had been totally discharged, after the first can of refridgerant was consumed the compressor kicked on. So it dosen't take much pressure to activate the switch.
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Re: A/C Switch on the Accumulator (mark79,80)
Dear Mark and Slide,
I already jumped the switch and the compressor comes on fine. I have about 100 pounds in the system when it is static. You may be right that the compressor will work just fine when I add a can; I just thought with that much pressure, I would get at least one click before it would switch itself off. I hate to put a can in the system to test it out, but unless someone has any better ideas, that may be what I should do.
I already jumped the switch and the compressor comes on fine. I have about 100 pounds in the system when it is static. You may be right that the compressor will work just fine when I add a can; I just thought with that much pressure, I would get at least one click before it would switch itself off. I hate to put a can in the system to test it out, but unless someone has any better ideas, that may be what I should do.
Melting Slicks
Joined: May 2002
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From: Sulphur LA
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
Re: A/C Switch on the Accumulator (virtue4u)
Virtu4u
The switch is designed to cycle the compressor at 18 to 20 psi, at this pressure using R-12 the evaporator coil temp. will be about 32 degrees if it is allowed to get below this the condensate will freeze on the coil and restrict the air flow. The port that the switch is screwed onto was equipted with a schrader valve in it. You schould be able to unscrew the low-pressure control switch without any loss of freon and replace it with a new one. When you replace the switch I would suggest replacing it with the car running and with the a/c on this way if the schrader valve fails the pressure in the system will be around 30 psi and not 100 psi. The only drawback to this is if the system is low of freon it will be operating in a vacuum on the suction side of the system and if the schrader valve has failed the system will draw air into it when you remove the low-pressure switch. If you have a set of a/c service gauges, bypass the low-pressure switch and check the pressure on the suction side with the system operating, and the car at idle, if the pressure is above 5 psi on the suction side you should be allright.
Be careful my 77 has a high pressure cut off switch it looks a lot like the low-pressure switch, but it is not mounted on the accumulator. Hope this helps.
The switch is designed to cycle the compressor at 18 to 20 psi, at this pressure using R-12 the evaporator coil temp. will be about 32 degrees if it is allowed to get below this the condensate will freeze on the coil and restrict the air flow. The port that the switch is screwed onto was equipted with a schrader valve in it. You schould be able to unscrew the low-pressure control switch without any loss of freon and replace it with a new one. When you replace the switch I would suggest replacing it with the car running and with the a/c on this way if the schrader valve fails the pressure in the system will be around 30 psi and not 100 psi. The only drawback to this is if the system is low of freon it will be operating in a vacuum on the suction side of the system and if the schrader valve has failed the system will draw air into it when you remove the low-pressure switch. If you have a set of a/c service gauges, bypass the low-pressure switch and check the pressure on the suction side with the system operating, and the car at idle, if the pressure is above 5 psi on the suction side you should be allright.
Be careful my 77 has a high pressure cut off switch it looks a lot like the low-pressure switch, but it is not mounted on the accumulator. Hope this helps.
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Re: A/C Switch on the Accumulator (chevymans 77)
Dear Chevyman77,
Yes, that does help, but I still have a question. With 100 psi in the static condition, shouldn't I get at least one click of the compressor if the switch was functioning? I know I'm low on freon (probably two cans), but with that kind of static pressure on the low side shouldn't the compressor initially kick on before the low side pressure falls to the point where the switch (if working properly) would shut the compressor down?
Yes, that does help, but I still have a question. With 100 psi in the static condition, shouldn't I get at least one click of the compressor if the switch was functioning? I know I'm low on freon (probably two cans), but with that kind of static pressure on the low side shouldn't the compressor initially kick on before the low side pressure falls to the point where the switch (if working properly) would shut the compressor down?
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Melting Slicks
Joined: May 2002
Posts: 2,717
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From: Sulphur LA
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
Re: A/C Switch on the Accumulator (virtue4u)
Yes any pressure over 18 to 20 psi on the suction side, static or with the system runnig should close the switch and engage the a/c compressor clutch, if the switch is operating correctly.
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Re: A/C Switch on the Accumulator (chevymans 77)
Still more problems. I can get the compressor to come on if I bypass the switch. I installed a new switch and freon, but I still cannot get the compressor to click on. The switch is in a tight place and may be under some physical stress against the fender when I plug it in, preventing it from working correctly. Tonight I am going to run wires from the switch to the plug or install an elbow from the accumulator to get the switch more out into the open. If that does not change anything, then I will try one more can of freon. If none of the above works, then I will concede to paying a mechanic. It just bugs me because I know its something simple.
Intermediate
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I see two things here. Compressor click on and off constantly: Most GM's are CCCS systems. aka: Constant Cycle Clutch System. Designed to function that way.
Secondly: If you jumper (the plug in wires, together) going to the low pressure switch and compressor kicks on; freon is low. 12 and 134 work the same. on pressure.
Also I have installed new & rebuilt compressors many times. Be sure to check the air gap between the pulley and the outer clutch plate. Varies from .19 to .27::: Magnetic power can only reach so far.
Secondly: If you jumper (the plug in wires, together) going to the low pressure switch and compressor kicks on; freon is low. 12 and 134 work the same. on pressure.
Also I have installed new & rebuilt compressors many times. Be sure to check the air gap between the pulley and the outer clutch plate. Varies from .19 to .27::: Magnetic power can only reach so far.
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
I see two things here. Compressor click on and off constantly: Most GM's are CCCS systems. aka: Constant Cycle Clutch System. Designed to function that way.
Secondly: If you jumper (the plug in wires, together) going to the low pressure switch and compressor kicks on; freon is low. 12 and 134 work the same. on pressure.
Also I have installed new & rebuilt compressors many times. Be sure to check the air gap between the pulley and the outer clutch plate. Varies from .19 to .27::: Magnetic power can only reach so far.
Secondly: If you jumper (the plug in wires, together) going to the low pressure switch and compressor kicks on; freon is low. 12 and 134 work the same. on pressure.
Also I have installed new & rebuilt compressors many times. Be sure to check the air gap between the pulley and the outer clutch plate. Varies from .19 to .27::: Magnetic power can only reach so far.
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
I applaud your can do attitude, however, changing the VIR is challenging for even able bodied experienced mechanics. First the refrigerant would need to be recovered, then the hard part is breaking the lines loose from the VIR, they can be corroded in place. Other than that, just the mount screws and it's out of there. You can gain some access from underneath by removing the lower access panel behind the right front inner fender.
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
Man you really know how to pick them. The fan shroud is probably one of the more frustrating jobs also. Is it the early or later design? On the early design, there is an extension for the shroud and not on the later. I remove the radiator on my 75 (same as early 76) and then the shroud.
Melting Slicks
Joined: Sep 2006
Posts: 2,814
Likes: 469
From: Wichita Kansas
I see two things here. Compressor click on and off constantly: Most GM's are CCCS systems. aka: Constant Cycle Clutch System. Designed to function that way.
Secondly: If you jumper (the plug in wires, together) going to the low pressure switch and compressor kicks on; freon is low. 12 and 134 work the same. on pressure.
Also I have installed new & rebuilt compressors many times. Be sure to check the air gap between the pulley and the outer clutch plate. Varies from .19 to .27::: Magnetic power can only reach so far.
Secondly: If you jumper (the plug in wires, together) going to the low pressure switch and compressor kicks on; freon is low. 12 and 134 work the same. on pressure.
Also I have installed new & rebuilt compressors many times. Be sure to check the air gap between the pulley and the outer clutch plate. Varies from .19 to .27::: Magnetic power can only reach so far.
