Question about the AC compressor
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Instructor
Joined: Nov 2013
Posts: 166
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From: Acworth GA
Question about the AC compressor
I just got my AC working on my 78. We put a new compressor and dryer on after the old compressor seized.
Question:
After the ac has been on for a while and the inside of the car is cool, should the compressor disengage if I move the temp control to the right (warmer). Mine does not seem to.
I know on some cars the compressor cycles to maintain temp and others use a bypass around the expansion valve to maintain temp.
Does anyone know for sure how this one works?
Also, if the system is overcharged a little, will it create a bigger load for the compressor?
Thanks
Question:
After the ac has been on for a while and the inside of the car is cool, should the compressor disengage if I move the temp control to the right (warmer). Mine does not seem to.
I know on some cars the compressor cycles to maintain temp and others use a bypass around the expansion valve to maintain temp.
Does anyone know for sure how this one works?
Also, if the system is overcharged a little, will it create a bigger load for the compressor?
Thanks
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
I just got my AC working on my 78. We put a new compressor and dryer on after the old compressor seized.
Question:
After the ac has been on for a while and the inside of the car is cool, should the compressor disengage if I move the temp control to the right (warmer). Mine does not seem to.
I know on some cars the compressor cycles to maintain temp and others use a bypass around the expansion valve to maintain temp.
Does anyone know for sure how this one works?
Also, if the system is overcharged a little, will it create a bigger load for the compressor?
Thanks
Question:
After the ac has been on for a while and the inside of the car is cool, should the compressor disengage if I move the temp control to the right (warmer). Mine does not seem to.
I know on some cars the compressor cycles to maintain temp and others use a bypass around the expansion valve to maintain temp.
Does anyone know for sure how this one works?
Also, if the system is overcharged a little, will it create a bigger load for the compressor?
Thanks
It continually spins.
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Instructor
Joined: Nov 2013
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From: Acworth GA
Took it out for the weekend up in the mountains. I have disconnected the lines to the heater so that there is not any heat coming in AT ALL.
The AC works great, but when I moved the control to the right it did not reduce the cooling. The air coming from the vents stayed very cold.
I would have assumed that this car would have some kind of sensor to detect that we were freezing in the car or that the temp control was try to communicate that we had enough ice cubes already and would automatically backed off the cooling. Is that a bad assumption? Is the only regulation device going to be my right hand to shut it off for a while?
The AC works great, but when I moved the control to the right it did not reduce the cooling. The air coming from the vents stayed very cold.
I would have assumed that this car would have some kind of sensor to detect that we were freezing in the car or that the temp control was try to communicate that we had enough ice cubes already and would automatically backed off the cooling. Is that a bad assumption? Is the only regulation device going to be my right hand to shut it off for a while?
1st Gear
Joined: Jun 2014
Posts: 1
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Took it out for the weekend up in the mountains. I have disconnected the lines to the heater so that there is not any heat coming in AT ALL.
The AC works great, but when I moved the control to the right it did not reduce the cooling. The air coming from the vents stayed very cold.
I would have assumed that this car would have some kind of sensor to detect that we were freezing in the car or that the temp control was try to communicate that we had enough ice cubes already and would automatically backed off the cooling. Is that a bad assumption? Is the only regulation device going to be my right hand to shut it off for a while?
The AC works great, but when I moved the control to the right it did not reduce the cooling. The air coming from the vents stayed very cold.
I would have assumed that this car would have some kind of sensor to detect that we were freezing in the car or that the temp control was try to communicate that we had enough ice cubes already and would automatically backed off the cooling. Is that a bad assumption? Is the only regulation device going to be my right hand to shut it off for a while?
that doesn't sound right. I don't know much about the system but my 81 toggles the compressor clutch to regulate temp.
Encore
Pro
Joined: Oct 2005
Posts: 505
Likes: 8
From: Houston Tx.
I believe there is the a/c pressure switch on the right fender that shuts the compressor down when the freon gets low and there is a compressor control switch on the plenum that senses the evaporator temperature to cycle the compressor. At some point, someone may have unplugged it and put a jumper in to make the compressor run all the time.
Thread Starter
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Joined: Nov 2013
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From: Acworth GA
I believe there is the a/c pressure switch on the right fender that shuts the compressor down when the freon gets low and there is a compressor control switch on the plenum that senses the evaporator temperature to cycle the compressor. At some point, someone may have unplugged it and put a jumper in to make the compressor run all the time.
Racer
Joined: Mar 2014
Posts: 316
Likes: 39
From: Machesney Park IL
2 things I would venture.
I think you have a CCOT, cycling clutch orifice tube, which means it should cycle the compressor clutch.
I also think you have a "reheat" system, meaning, unless you are on Max cold, the air also goes through the heater core, warming it up a bit before putting it into the cabin. If the water valve is off, you will be on "MAX" at all times for cold air.
You should have a low pressure cut out switch, that shuts the system down if the pressure is too low, and a thermostatic switch, which I believe is what cycles the compressor, clamped to the evaporator line.
I think you have a CCOT, cycling clutch orifice tube, which means it should cycle the compressor clutch.
I also think you have a "reheat" system, meaning, unless you are on Max cold, the air also goes through the heater core, warming it up a bit before putting it into the cabin. If the water valve is off, you will be on "MAX" at all times for cold air.
You should have a low pressure cut out switch, that shuts the system down if the pressure is too low, and a thermostatic switch, which I believe is what cycles the compressor, clamped to the evaporator line.
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From: Southbound
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From: Acworth GA
I also think you have a "reheat" system, meaning, unless you are on Max cold, the air also goes through the heater core, warming it up a bit before putting it into the cabin. If the water valve is off, you will be on "MAX" at all times for cold air.
You should have a low pressure cut out switch, that shuts the system down if the pressure is too low, and a thermostatic switch, which I believe is what cycles the compressor, clamped to the evaporator line.
You should have a low pressure cut out switch, that shuts the system down if the pressure is too low, and a thermostatic switch, which I believe is what cycles the compressor, clamped to the evaporator line.
I looked and there is something on the AC low side line. It has wires attached to it. One of them is the same color as the compressor wire. This looks like a good place to start.
Thanks
Race Director
Joined: Sep 2001
Posts: 10,560
Likes: 439
From: Wellington, FL
St. Jude Donor '11 thru '25
Took it out for the weekend up in the mountains. I have disconnected the lines to the heater so that there is not any heat coming in AT ALL.
The AC works great, but when I moved the control to the right it did not reduce the cooling. The air coming from the vents stayed very cold.
I would have assumed that this car would have some kind of sensor to detect that we were freezing in the car or that the temp control was try to communicate that we had enough ice cubes already and would automatically backed off the cooling. Is that a bad assumption? Is the only regulation device going to be my right hand to shut it off for a while?
The AC works great, but when I moved the control to the right it did not reduce the cooling. The air coming from the vents stayed very cold.
I would have assumed that this car would have some kind of sensor to detect that we were freezing in the car or that the temp control was try to communicate that we had enough ice cubes already and would automatically backed off the cooling. Is that a bad assumption? Is the only regulation device going to be my right hand to shut it off for a while?
Last edited by Jud Chapin; Jun 23, 2015 at 04:53 PM.
Thread Starter
Instructor
Joined: Nov 2013
Posts: 166
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From: Acworth GA
My mistake, the "something" (I guess a sensor) is on the high side line. It's after the coils up front and before the coils inside the car.