1999 p38. a/c problem. [Compressor cycles on and off about every 60 seconds.] Blows cold on start up; but, starts this cycling after about 20 minutes. Have cleaned radiator and condensor. WD 40 on high and low pressure switches, plus replaced relay. Compressor and dryer nearly new. Everything works in the beginning. Book light comes on shortly after start up, the blower starts up. Compressor has already kicked in. Blower blows on high and very cold and after short time will not blow on high. The weather is vey hot and humid in Louisiana. Pressure on guages rise to about 305, fans kick in. Shortly after this the compressor kicks out. Yet, I am the proud owner of 3 P38's. This is over my head. Could some of you BRITS help this Irishman. Thanks, Wolfe

WHEN IT QUITES COOLING CHECK THE AC HOSES THAT GO INTO THE CAB TO SEE IF THEY ARE ICED. You may have a system that is not cycling the compressor when the temp drops to keep it from freezing.

Low freon will cause the compressor to short cycle, when the compressor runs the pressure in the low line is pulled down and the low pressure switch turns it off. Not running the pressure builds up and turns it back on. In the old days there was no low pressure switch, with no freon to carry the oil the compressor was destroyed.

probably wants re-filling.

I would replace the AC compressor cycling switch it may be sticking have seen it a number of times. The switch is located in the receiver dryer on the passenger side of the engine compartment. See picture below.

If this isn't the problem the AC compressor relay may also cause this, flip a coin.

This is most likely the cycling of the AC unit. As the compressor pressurizes the 134a Freon you get the cold air, once it reaches a certain pressure it cuts out. If you are low on Freon it will cycle out more often. Check your freon level with a gauge to see if your within the proper tolerance. If the compressor runs for a period and doesn't reach the right pressure it will cut out to keep from damaging your compressor so it is important to keep the correct amount of freon in the system.

I would check the following possibilities:
1. Is compressor clutch working? - You need to do this when the ac is blowing hot air only - locate compressor drive pulley on engine - rubber belt wraps around it. Start engine and set to max ac. When the ac is blowing hot air, look at the center of the compressor drive pulley using a good flash light - watch it for a while, it should be spinning with the pulley - this means the compressor is engaged. If not, the compressor is not engaged. If your ac is blowing hot air, then the compressor should be engaged and running (trying to cool). If it is not engaged, then your compressor clutch is probably going out. Could be low voltage to clutch, but more likely the clutch is worn out and only working some of the time. Note: if working normally, the compressor clutch will engage and disengage in cycles- but the air should always be cold. If clutch is bad, compressor would need to be replaced (sold as one unit). This is tricky to diagnose and could take some time - you need to do it when ac is blowing hot air but set to max cooling.

2. Low on refrigerant or refrigerant has moisture in it? If your ac blows cold initially after being off for a while, then heats up, and continues to regularly cycle back and forth between hot and cool air, then the system may be low on refrigerant or the refrigerant may have moisture in it that is freezing and restricting refrigerant flow. An a/c shop can check refrigerant level and even replace refrigerant if moisture is suspected.

Could be other issues, but I would start with these.

Good luck

the tracer is the same as the ESCORT, right?? TRY THIS--I WORK ON PLENTY OF ESCORTS--LOOK UNDER THE AIR CLEANER/CONE ASSEMBLY--THERE WILL BE A BLACK METAL BOX(FULL OF RELAYS) ONE OF WHICH IS THE A/C RELAY--TRY TAPPING ON IT WITH A LONG SCREWDRIVER OR SOMETHING SIMILAR WHILE U HAVE THE A/C ON. IF THE A/C SUDDENLY STARTS WORKING U NEED TO GET A NEW RELAY BOX(I THINK ITS CALLED A GEM MODULE) i do have a question- does the blower motor work?? how do u know the compressor is good??do you have 12 volts going to it??? this relay box is pretty common to go bad--u have to remove the air cleaner in order to get to it.get back to me.

After the A/C turns hot , check to see if compressor is still cycling. If not the system may need recharging.

Could be low on freon. Or the cycling switch is bad. Hope this helps.

I think what happens is that you're burning out the compressor. If you got the windows down while you're blowing the a/c? it's working over time which is why they have two cycles. The image that displays the circle motion is meant for the windows to be up and the charge will last longer and with the windows down...click the one that shows outside air coming into the car. It might not be as cold as the other option but at least you'll have some cool air while you're at it.