Do I need a new a/c compressor? | Ford Explorer Forums - Serious Explorations

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Do I need a new a/c compressor?

chipmiller2000

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Joined
July 21, 2009
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City, State
Macon, GA
Year, Model & Trim Level
'97 XLT
I recently purchased a '97 Explorer with 4.0 OHV. The a/c is not cooling. Both high and low side read 100 psi with engine off. With engine on, the a/c clutch cycles every 5 seconds but only stays on about 1 second. With clutch on the low side drops to 25 psi and the high side goes to 140. With clutch off the low rises to 45 and the high drops to 125. It will not receive any refrigerant and it does not cool the car at all. Although there are no signs of refrigerant leakage, does it sound like I should replace the compressor? Thanks.
 



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I think you are just low on refrigerant at this point. Though refer is always added to the low side, the pressure on the high side should be higher than 140 (perhaps about 225psi at 90 deg f) 0n the high side and the compressor isn't showing much sign of strain as of yet.

First off the high and low sides are supposed to be equal with engine off.

I would doubt at this time that you have a bad compressor as it seem to be doing its job.

On shut off it should take about 90 psi at 80deg f to show liquid freon in the system and satisfy the the low pressure (sensor)switch. On most systems the compressor will shut off at about 20psi and on about 45 psi.

Rapid cycling indicates low pressure. The high side should measure about 2.5 times the ambient temperature. In other words if the average temp by the radiator and inside the car is 90deg f then 2.5x90deg=225psi. The low side will be about 45psi.

I hope this is a start. (thank you for providing enough info)
 






thanks robertoa1a. Any ideas how I can get the system to take the refrigerant? When I hook everything up to recharge the system, it does not recharge. Could a bad orifice tube prevent recharging to take place?
 






If it were a clogged orifice I would expect the high side to read above normal or unequal static pressure. Some times It takes a while because the compressor isn't staying on long enough yet to take in the freon.

You want it on A/C max, fan on high, and windows down. You can turn the freon cylinder up-side-down briefly so that straight liquid is going into the system. You will notice the compressor clutch cycle getting longer and longer as pressure builds up.
 






I just re-hooked up the guages and refrigerant container and still no charging takes place. I put control on max a/c, put a jumper wire in the switch near the accumulator which resulted in the compressor clutch running continously. This brought low side down to a consistent 8 psi and the hight stayed at 150....but I still cannot get it to take the refrigerant as evidenced by the sight glass, the can remaining warm, an the a/c temp remaining warm. I allowed it to run about 20 minutes. Any other ideas? I do own a vacuum pump and have thought about slowly releasing what air is in the system and then vacuuming it down. Thanks.
 






Something isn't making since. With only five pounds on the low side it should be taking freon fast. It sounds like a valve is shut off on your gauges or the valve on your freon container is bad.

The A/C system seem to be functioning normal under the circumstances. The refrigerant level is low on both sides. You just have to figure out why Your equipment isn't filling the system.

It sounds like you know what your doing otherwise.

You don't have the high side valve open do you?
 






You'll be cold pretty soon. The Explorer has a awsome A/C unit.
 






Robertoa1a...I read your reply and agreed out loud "something isn't making sense" about this. Brilliant mechanic I am, I re-checked the refrigerant line and found I had not connected it to the shrader valve and therefore was not getting any flow from it. Reconnected to correct valve...2 cans of R134 later my Explorer is cold as ice. Thanks guys for saving me a few hundred dollars worth of unnecessary a/c parts. I will later check for leaks with hopes of finding the bottom line cause of the refrigerant being low in the first place.

This forum is great.
 






One more note...with the a/c running and cooling, the low side is reading 48 and the high 300. It's about 90 degrees outside. Sound o.k.?
 






That is slightly high. Too much is not good either because you don't get as much expansion and its hard on the compressor. At 90deg it should be around 45psi low and less than about 240 on the high. Now that the engine is hot It could be 120 degrees under the hood so maybe 300psi on the high is okay.

If you let just a little pressure out it may purge out any air that might be in the system.
 






Thanks. Will do. Since I assume the previous owner had not charged up the system for over a year, would you add a can or two of oil now as well? If so, what viscosity?
 






It sounds like it leaks 2 cans every 13years. Good luck finding the leak. LOL

No, on the oil. The oil pretty much stays in the compressor and its a special oil that works specificly with r134a.
 






Sorry. He said he had to charge it annually, but had not done so this past year since the car had sat in his yard unused awaiting him to sell it.
 






Maybe your parts store has a halogen detector (sniffer) that you can borrow. I fix mine in the winter when everything is about half the price it is now. Since you live in warm weather you can do that but not on a cold day. The psi numbers will be a lot lower in cooler weather.
 






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