1985 A/C diagnosis
Thread Starter
Drifting
Joined: Mar 2017
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From: Nashville TN
2017 C4 of Year Finalist
1985 A/C diagnosis
It's getting to be summer, so it's getting HOT outside here. I wanted to get my A/C working. When I turn it on, I get...cool...air through the vents. Blower motor appears to be working, and the air coming out of the vents isn't cold, but it's slightly cooler than ambient temp.
Added R-12a refrigerant to the low pressure nozzle, and my gauge jumped to 110 PSI-which sounds like too high pressure to me, but I'm not sure. Pressure didn't go up at all from the can, so I suppose it's not going to. All of this was done with car running and A/C on max.
Temp of A/C is still a little cool, but definitely wouldn't call it cold, just slightly less than ambient. Any thoughts? I've never done anything with A/C but add R-134a to my daily driver before, explain like I'm 5 please
Added R-12a refrigerant to the low pressure nozzle, and my gauge jumped to 110 PSI-which sounds like too high pressure to me, but I'm not sure. Pressure didn't go up at all from the can, so I suppose it's not going to. All of this was done with car running and A/C on max.
Temp of A/C is still a little cool, but definitely wouldn't call it cold, just slightly less than ambient. Any thoughts? I've never done anything with A/C but add R-134a to my daily driver before, explain like I'm 5 please
Thread Starter
Drifting
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From: Nashville TN
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Team Owner
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From: Outside the Quick Stop N.J.
The low side fitting is on the line from the compressor to the accumulator, the high side is on the line from the compressor to the condenser. Do you have a manifold gauge set, or just one gauge ?
Burning Brakes
Joined: Nov 2016
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From: Buchanan GA
The suction accumulator is what I think you are referring to and yes, that should be low side pressure.
110 psi is high for the suction side if the compressor is actually running and pumping. It would be right on for a system that is off on a hot day or in a hot engine compartment. Any way you might have been reading the pressure in the can and not the system? Could you tell that the refrigerant left the can and went into the system?
Can you hear the compressor clutch engaging and the compressor running? Is the discharge line hot going to the condenser?
110 psi is high for the suction side if the compressor is actually running and pumping. It would be right on for a system that is off on a hot day or in a hot engine compartment. Any way you might have been reading the pressure in the can and not the system? Could you tell that the refrigerant left the can and went into the system?
Can you hear the compressor clutch engaging and the compressor running? Is the discharge line hot going to the condenser?
Le Mans Master
Joined: Jan 2006
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From: Orlando FL
Added R-12a refrigerant to the low pressure nozzle, and my gauge jumped to 110 PSI-which sounds like too high pressure to me, but I'm not sure. Pressure didn't go up at all from the can, so I suppose it's not going to. All of this was done with car running and A/C on max.
Are you using a 12oz can to fill, what is your setup?
Be careful those cans or whatever your using because they aren't designed for those pressures and may blow out on the bottom where there is a relief cut out, but you don’t what to go there.
110 psi is to high for the low side, and to low for the high side.
That sounds like a static pressure reading with the compressor not turning at all. Before you hook anything up and as said, check to see if the compressor center shaft is actually turning.
If the Freon charge is too low, the cycling switch will not turn on the compressor if all is working properly. The cycling switch if defective and will not close, this will prevent the compressor from coming on. In any event check the compressor to see if it's turning FIRST.
If the compressor is not turning, you are going to have to figure out first why before you try to add Freon again.
Thread Starter
Drifting
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From: Nashville TN
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how can you tell if the compressor is turning? And if it is NOT turning, what are some possible causes to check?
Thanks for the replies, I'm really stupid when it comes to A/C
Thanks for the replies, I'm really stupid when it comes to A/C
Le Mans Master
Joined: Jan 2006
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From: Orlando FL
There is an outer ring or pulley that always turns when the engine is turning. Inside of that is the shaft and clutch for the compressor. It's either going to be still, or turning at the same speed that the outer pulley is turning. Get a flashlight and keep your fingers out of it.
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Le Mans Master
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From: Orlando FL
Just wanted to add if the compressor is not turning and you (somehow) measured 110 psi, then there is enough Freon in the system to close the low pressure switch. IF that is the case, then we need to figure out why the compressor is not coming on.
Thread Starter
Drifting
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From: Nashville TN
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I jumped the low pressure switch, there was a dip in the engine speed a little, I thought that was the compressor kicking in but apparently not.
Burning Brakes
Joined: Nov 2016
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From: Buchanan GA
You should be able to tell from the clutch on the front of the compressor if it is turning or not. If it is idling it won't be turning.
Burning Brakes
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What should the high/low pressures be for a 1985 still using R-12?
The FSM that I have does not give these pressures instead gives some vague explanation about the "feel" of the temperature of the A/C lines.
I apologize for the hijack of this thread but felt I didn't need to start another thread about the A/C on a 1985.
Thanks.
The FSM that I have does not give these pressures instead gives some vague explanation about the "feel" of the temperature of the A/C lines.
I apologize for the hijack of this thread but felt I didn't need to start another thread about the A/C on a 1985.
Thanks.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
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From: Orlando FL
Very similar to cars using R134. Except the cycling switch for R12 should open at 25psi (rather than 22.5 with 134). The closing of the switch is about 50 psi but not overly critical (about 46 for 134). This is read with gauges on the low pressure port with the engine running as well as the compressor. Amount of charge, ambient temperature, fan speeds and air flow over the condenser all will vary the amount of cycling time per minute.
Simplistically the feel is the "fat lines are cold and the thin lines are hot". But to an experienced person more can be determined by feel as an indication the system might be low on Freon or some other abnormalities. Of course feel does not by any means substitute a set of gauges and a knowledge of how to interpret then (not just look at the numbers).
The FSM that I have does not give these pressures instead gives some vague explanation about the "feel" of the temperature of the A/C lines.
I apologize for the hijack of this thread but felt I didn't need to start another thread about the A/C on a 1985.
Thanks.
I apologize for the hijack of this thread but felt I didn't need to start another thread about the A/C on a 1985.
Thanks.
Last edited by pcolt94; Jun 5, 2017 at 04:20 PM.
Thread Starter
Drifting
Joined: Mar 2017
Posts: 1,897
Likes: 165
From: Nashville TN
2017 C4 of Year Finalist
Thread Starter
Drifting
Joined: Mar 2017
Posts: 1,897
Likes: 165
From: Nashville TN
2017 C4 of Year Finalist
Oil Producer
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says here in this thread that when the system is off, ie, compressor off, the pressures will equalize. understandably.
here is a link to the post but you should read the thread.
https://www.corvetteforum.com/forums...post1566015606
id verify all switches and electricals are functioning.
id start by unplugging the two blade plug from the top of the ac compressor, put my volt meter on the harness, then i would turn the car on with defrog on, which should activate the compressor, then jump the low pressure switch like you did before, and you should see 12v show up on the volt meter that is attached to the ac harness plug.
let us know.
here is a link to the post but you should read the thread.
https://www.corvetteforum.com/forums...post1566015606
id verify all switches and electricals are functioning.
id start by unplugging the two blade plug from the top of the ac compressor, put my volt meter on the harness, then i would turn the car on with defrog on, which should activate the compressor, then jump the low pressure switch like you did before, and you should see 12v show up on the volt meter that is attached to the ac harness plug.
let us know.
Last edited by VikingTrad3r; Jun 5, 2017 at 01:26 PM.