a/c question
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a/c question
The a/c in my Explorer 94 4.0L V6 does not cool at all. I tried to recharge it with a Kit from auto store with a guage in it, and as soon as I connected it to the low side valve (by the evaporator, fire wall), it indicated 110 psi in the red. I did not even use the can, the instructions said should not be more than 45 psi. Would any body have any idea why it read so high? I would appreciate any help.
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From: Pauline, South Carolina
Was the compressor running at the time? If the compressor was not running, the pressure on both the low and high side will be at the vapor pressure for the refrigerant corresponding to the average ambient temperature, assuming that the system still has refrigerant in it. If the compressor was running, it does not sound as if it was working and I would suspect compressor issues. If it was not running, and the A/C was turned on, I would check to see why it was not running. If there is no voltage to the compressor clutch then first I would jumper across the low pressure switch to see if it was bad (110 psi should certainly be sufficient). Then if that was not the issue I'd look around the switch and wiring. (Oh and make sure the wire is plugged up to the compressor clutch, I once fixed a friends A/C over lunch by simply plugging up the wire)
Good Luck.............
Good Luck.............
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I thank you Jerry. Yes, the engine was running and the A/C was on, however, does not mean the compressors was working. From what you said, probably was not, but if lost all the refrigerant, wouldn't the pressure switch keep the compressor from running? If this the case, what would you suggest I do? Charge the refrigerant against 110 psi?
Hugo
Hugo
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From: Pauline, South Carolina
No, it will not charge. With the engine running and the A/C turned on, look at the compressor and see if the center of the pulley is turning. There is an electromagnetic clutch that engages to allow the outer pulley to turn the compressor. There should also be a sound associated with the compressor working. I apologize if my first message was confusing, but I was not suggesting that your system has lost all of it's refrigerant. Obviously since there is pressure it has not. There is also more than enough pressure at 110 psig to engage the low pressure switch. On your reciever dryer canister, there is a switch with two wires plugged into it. This switch will not allow the compressor to run if the low pressure in the system falls below a certain level (usually around 25 to 30 psig). That is to prevent system damage that can result from running with insufficient refrigerant. If your compressor is cycling on and off it's usually the result of low refrigerant causing this switch to cut out when the compressor drops the pressure and then re-engage when the pressure equalize. Anyway, the key to begin troubleshooting is to see if the compressor shaft is actually turning.
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Jerry, you were right, the compressor was not engaging. Reason: the shop that checked for a slow leak left the pressure switch unplugged. Now, my stupid question is: Pressure is getting on the low side, I know I have a slow leak and am planning on finding it, but when I recharge, what if the pressure starts getting too high and the can is still going? If I disconnect the can, would it discharge into the atmosfere? Is there any way to stop it?
Hugo
Hugo
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Simply close the valve on the can. Leave everything sealed up and disconnect the hose. Remember that prior to charging the system you should slightly purge the hose to minimize the air that may be put into the A/C system. You may want to consider charging the system using a leak detector charge, that can help find the leak. Also, if it is a slow leak, there are some leak stop charges on the market. Note that on some of these additive charges you may have to perform a liquid charge instead of a gaseous charge. That simply means to hold the can upside down for liquid or right side up for gas. Be careful if doing a liquid charge, because if there is insufficient time and volume for it to expand to gas before entering the compressor as liquid does not compress and can damage the unit.
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Jerry, what am I doing wrong? I connected the can to the low side of the A/C system, w/ engine and A/C running. Initially, the guage read 25 psi, (border line filled and low), as soon as I pierced the can with the needle valve, the pressure shot to about 100 psi on the red and seemed to increase slowly, so I decided to disconnect everything and ask a few more stupid questions.
I measured the pressure again w/out the can and it read only 25 PSI. It seems to me I was reading the can pressure not the system's but the refrigerant did not seem to go in. The fact that I can read system pressure tells me that the low press valve is being open, so what do you think is happening?
I appreciate your help greatly.
Madeline.
I measured the pressure again w/out the can and it read only 25 PSI. It seems to me I was reading the can pressure not the system's but the refrigerant did not seem to go in. The fact that I can read system pressure tells me that the low press valve is being open, so what do you think is happening?
I appreciate your help greatly.
Madeline.
Last edited by Madeline; Sep 9, 2004 at 06:25 PM.
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From: Pauline, South Carolina
Check your connection on the low side. It sounds like you're not flowing much from the can into the system. However, you are flowing some, because the pressure does drop to 25 psig. Did the 94 originally come with R-134 or is it a converted R-12 system. I've had some converted systems where the low side adapter made for a difficult connection. Don't get hung up about the pressure going up. If you're using one of the small cans and the compressor is cycling there is very little chance of overcharging the system with 1 can. Also, if you're performing a liquid charge, it is normal for the pressure to jump up. That's because the liquid must vaproize in the system and it will typically not do that until it has gone through the schrader valve and into the larger volume of the low pressure system.
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From: Ardmore
What is the high side running? Do you have a guage for the high side? When you open up the connection to the can the low side guage will read the can pressure. You can not go by the reading while the can is full and the valve is open. Does the can get cold when you are trying to charge the system? If it does refrigerant is going to the system. Does the system cycle on and off? 25psi low side pressure is a little low but this could be caused by a number of problems, including low refrigerant.
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