Air conditioner problems
Thread Starter
Pro
Joined: Apr 2008
Posts: 681
Likes: 11
From: Carson City MI
Air conditioner problems
On my 81 I have converted to 134r. The system is full and not leaking.
When I switch on the air, the compressor clutch kicks in and runs for only a couple of seconds then kicks off. It just continues to cycle this way. The lines get cool but not cold and no noticably cool air in cabin.
Any suggestions?
When I switch on the air, the compressor clutch kicks in and runs for only a couple of seconds then kicks off. It just continues to cycle this way. The lines get cool but not cold and no noticably cool air in cabin.
Any suggestions?
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
might be a little short on freon. There is a switch on the low pressure side that forces the clutch to cycle if the pressure is to low because of low freon or if the evaoprator starts frreezing up and causes a low pressure on the low side. Your going to need to get a set of gauges on it to see what its doing.
Race Director
Joined: Sep 2001
Posts: 10,560
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From: Wellington, FL
St. Jude Donor '11 thru '25
And you'll also have to jump that switch so that the compressor engages full time in order to get a reading from your gauges. Out of curiosity, what makes you think you are not low on refrigerant?
Thread Starter
Pro
Joined: Apr 2008
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From: Carson City MI
I tried to add more last night and it reads full on the gauge and won't take any more. Actually on the high side of full.
Drifting
Joined: Apr 2008
Posts: 1,305
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From: Lewisburg WV
thegazman
What are the pressures on the low and high side? What is the ambient temperature where you are charging the system? Sixfooter is right...it sounds like the low pressure switch. When you converted to 134 did you evacuate the system long enough to insure there is no moisture present?
Thread Starter
Pro
Joined: Apr 2008
Posts: 681
Likes: 11
From: Carson City MI
What are the pressures on the low and high side? What is the ambient temperature where you are charging the system? Sixfooter is right...it sounds like the low pressure switch. When you converted to 134 did you evacuate the system long enough to insure there is no moisture present?
Thanks..
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
There is only 1 pressure switch and its on the low side. Disconnecting the switch in effect opens the circuit and the clutch will drop out, you have to put a jumper across the switch contacts to bypass it to engauge the clutch and make the system take more freon. From empty the system is supposed to take 3.75 lbs of R12, you need to de-rate that to about 80% (I think) so just over 3 lbs of R134. If you put in less than that your system is low on freon which will cause the low pressure switch to drop out the compressor early and it will cycle rapidly.
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Drifting
Joined: Apr 2008
Posts: 1,305
Likes: 2
From: Lewisburg WV
thegazman
Sixfooters infomation is right on. He's obviously very knowledgeable regarding A/C principles. To simplify it for you...remove the plug from the low pressure switch. Take a piece of wire 4" to 5" long, remove 1/2" of insulation from each end. Twist the wire and plug it into the plug you removed from the low pressure switch. Start the car and turn the A/C on. If the compressor continues to run steady (without cycling). You are low on refrigerant. Leave the jumper wire in the plug while you add more 134 as it will help by reducing the pressure on the low side of your system allowing you to add refrigerant more easily. If you're charging with small cans, you can lay them on the engine. The heat will increase the pressure in the can helping to overcome pressure in the A/C system. But, don't do that until the can is down to about 1/4 full. Or 3/4 empty.
Le Mans Master
Joined: Aug 2003
Posts: 7,720
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From: Chattanooga TN
You can also put the can (upright) into a pan of hot tap water.
Thread Starter
Pro
Joined: Apr 2008
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From: Carson City MI
Thanks for all your replies. I did check my gauges and I am hitting 50 lbs but when the clutch kicks in it drops to 25. I am now sure that I am low and went out last night to put a jumper wire on the switch and try again. I made the jumper wire and that was as far as I got, due to my wifes vehicle occupying the garage space and the five torrential thunder storms moving through the area. I am dedicated, but with trees falling all over the neighborhood, didn't think it wise to proceed. Besides, I had just painted my engine block and polished all the engine chrome and was not about to open that hood in a driving rain storm.
Clearing today and I will assault it tonight so I can hopefully cruise on the 4th in cool comfort.
I wish a happy and safe holiday to all of you.
Carl
Clearing today and I will assault it tonight so I can hopefully cruise on the 4th in cool comfort.
I wish a happy and safe holiday to all of you.
Carl
Drifting
Joined: Apr 2008
Posts: 1,305
Likes: 2
From: Lewisburg WV
thegazman
I'm not sure what the pressure temperature relationship chart shows for 134, but 25 pounds I'm sure is too low. R12 needs to be approximately 35 pounds to be above freezing, so I'm sure your low pressure switch won't stay engaged until you reach approximately 35 pounds steady pressure while the A/C is running as it's designed to operate for R12. I think 134 is slightly higher to reach the above freezing point. If you look up R134a pressure temperature relationship there will be a chart to tell you what you need to be at to be above freezing.
Drifting
Joined: Jun 2005
Posts: 1,523
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From: grand prairie texas
Also A few tips if you are still using the engine driven fan run water across the condensor while you are checking your pressures. The condensor will get real hot without adequite air passing thru it. Depending on how hot it is where you are at the low side will be up around 50 and the high side will be up around 250. These presures will come down by cooling the condensor