97 XLT 4x4 Explorer Strange A/C problem

Hi, I'm new here but am having some trouble with my a/c and wanted to see if anyone has any ideas? I have a 97 XLT 4x4 Explorer, the a/c was having a problem where it would blow cold sometimes but then would just stop and blow what felt like, just vent air. I thought I was just getting low on freon so I took it to Allied and they replaced some parts, flushed the system, and added new freon. Well, after I drove off it would still do the samething...when it blows cold, its really cold but then it will just stop and turn warm. I took it back to the mechanic the next week..he drove it around but it didnt do it to him...they went ahead and rechecked for leaks and added some more freon. He told me if it still kept doing it, the only other thing he could think of was that the evaporator (I think) could maybe be clogged with debris or sludge and they could try cleaning it or replacing it...and it will cost around $450. Does that sound like a cause or could it be anything else? The compressor is fine and there are no leaks that they could find. Thanks in advance for your help and info. I dont' think so. If the evaporator was clogged with debris the problem would not be intermittent. If it were that then you’d notice very little airflow out the vents.

Did the mechanic test any of the pressure switches on the system? It sounds to me like one of them isn't functioning properly all the time.

There is a pressure switch on the low side that will turn the system off if the pressure gets too low (generally signaling a low refrigerant condition). There is a pressure switch on the high side that will kick the system off if the pressure gets too high (generally signaling an overcharged system or a non-functioning cooling fan).

If either of the pressure sensors are not reporting correctly it'll kick the system off even if there is a full and proper refrigerant charge.

Make sure the electrical connections at both pressure switches are clean and secure.

Good luck. Ok...that definately sounds more logical to me. Are these switches easily viewable? Where would they be? Could they just be replaced and if so do you know of anyplace online that I could order them from? Thanks again for your help and info. You can't mistake the switches once you see them.

I am not familiar with your particular vehicle but if you follow the refrigerant lines there will be doodads with wires plugged into them. I've never had the displeasure of a malfunctioning pressure switch so I've never changed one. (But you can test a non-intermittent switch problem by jumping the wires in the connector running to the switches.)

The tough part is going to be testing for an intermittent switch problem.... I hate to suggest a guess part; and I don't even know how much they cost. I believe they are threaded in and I've heard the refrigerant needn't be removed to change them. (I am not quite sure how that's possible unless there's a valve in there somewhere.)


You could run long continuity test leads to the passenger compartment and see if the switch opens when the a/c quits on you..... Mount the continuity tester on the hood with a good magnet? Heck, with the proper (expensive) computer equipment you could probably monitor both switches from the scan port.


Of course, if you find a switch is opening when the a/c kicks off it could be reporting correctly. If the high switch is opening then there could be an internal clog. Same thing for the low side switch. If there's a clog inside the system the pressures can get funky.

Of course then you'd need to hook up pressure gauges to monitor the pressures (optimally while going down the road). But the gauges are not too cheap. It'd probably be cheaper to replace the pressure switches and believe them if you find one of them is opening the switch.

Have you ever had problems with this a/c system before? Also system could be freezing causing blockage.Check to see if suction accumulator is iced when this happens.The accumulator is the black tank where the low switch is. If this is the case it could be that your compressor constantly runs, and does not cycle as it should therefore it could be a sticking relay. I have a 97 XL and was having a similar problem. But before I take it anywhere I posted on this board so I would know what I was talking about if I took it in. Just when I was prepared to take it in for testing I jiggled the switches and it kicked in. Trouble is when it kicks off it does not always come back on.

Now I notice that when I tap the metal part on the switch it kicks in. I may just replace the switch and go from there for now. This vehicle only has 50,000 on it and came from a city that would probably not use the AC much. I agree with the last response. The low pressure switch on the accumulater or drier will cause the problems that you are having. I have changed the one on my 1990 Chevy truck a couple of times. When the a/c cools down and the pressure gets low the a/c compressor will cylce off to keep the evaporater from freezing up. When the pressure comes back up (usually within 5 seconds or so) the switch should close and the compressor kick back on. You can tap the switch with a screwdriver or something after the compressor kicks off and will not come back on. Make sure that you have a good connection at the switch. If the compressor comes on the switch is probably bad. They are very easy to change and cost around $10-$15. There is a schrader valve on the accumulator that will keep you from losing any freon.

good luck