A/C Compressor Cycling Mystery!

[King Tut]

97 4.0L Explorer Sport

The A/C compressor is cycling on/off every 2 seconds. There is plenty of coolant pressure and the relay and switches have been checked and bypassed.

It turns out that the computer is signaling the relay to turn off the compressor after 2 seconds or so when it kicks in. This has been verified at the fusebox relay with a test light.

Is there something else in the car or computer that would cause this to happen ?? We have plugged in the computer diag and noticed nothing out of the ordinary except an intermitant "off" signal to the A/C unit control.

Any Ideas on what else might be telling the computer to shut off the A/C compressor ??

Thanks for any thoughts...

Ron

 

[Glacier991]

"There is plenty of coolant pressure"... with due respect the pressure on a non-operating system really tells you little. I'd first want to know what the low and high sides do when the system engages (even if just for a couple of seconds). Next I have to wonder about the WOT (Wide Open Throttle) module. I am not sure but I also think the control module will turn off AC if it is sensing an engine overheating condition - rightly or wrongly (someone else may be able to verify that).

 

[King Tut]

Thanks for the fast reply...

According to the mechanic working on it:
High side is 90 - drops to 80 and then kicks off immediately.
The WOT Module was checked and responded fine. We also bypassed and it is working OK. This was done with computer diag plugeed in.
System temp was also tested at 187 F, so we ruled out overheating.

Any other ideas ?? Could the computer be giving it a bad command ??

Ron

 

[ToughCountry]

i have the exact same thing goin on with my 97 X. ive been wonderin whats the problem is also

 

[Glacier991]

Still wanna know the low side readings operating.

 

[gensic11]

same thing happens to me.. does it make ur car almost die as well?

 

[ToughCountry]

my truck doesntg almost die but it just clicks every couple seconds spins then stops over and over again

 

[Glacier991]

This is not NEW news... but in the usual drill on this is that a compressor very low on charge will do this. Do a search <concept? using the serach term AC and you will uncover a goldmine of information, most of it telling you that a quick cycle means low charge. (except at cold temperatures, in which case a fast cycle usually is normal on the FORD FOV (fixed orifice valve) system)

 

[King Tut]

High - Low Readings

A clarification...

The high and low both start at 90

The high goes to 100 and the low goes to 80 after about 1-2 seconds
Then it cycles and starts over. The computer is sending the cycle signal to the relay. We have determined this with a test light.

Thanks for your thoughts…We are stumped and are beginning to think the computer is screwing up...

Ron

 

[King Tut]

Still stumped...

The latest...

We attempted to put in some coolant with Red Dye to see if there were any leaks in the A/C system. It didnt appear to leak out anywhere and didnt take too much of it anyway. We are fairly confident that it is full.

At first glance the accumulator tank (covered in foam) that others have mentioned as a source of leaks, appears to look good. I didnt do a complete inspection of it due to the fact that there doesnt seem to be any leaks in the coolant but it looks clean and solid.

Looking for more ideas...

Thanks

Ron

 

[ScottLemieux]

Ron,

I am curious if you have found the solution? I have the exact same problem and cannot fiqure it out.

Thanks,
Scott

 

[friech]

I had similar symptoms last year but luckily for me it was only due to a low charge. An additional can of coolant significantly lengthened the amount of time that the compressor would stay on.

 

[97BlackX5.0]

yeah its almost for sure the accumulator... mine is having this problem.... i had to put in a can of coolant and it will be good for about a month.... then its time for another can... planning on fixing it this fall cause im away from my tools/ garage right now... btw coolant is 3.68 for a 12 ounce can at walmart right now.... coupled with my 10 percent discount i get it it for roughly 3.30 a can.... i feel like smacking a mechanic whenever he tells me that r134 is 25 bucks a pound......they can buy a propane sized cylinder of it for 50 bucks......

 

[seanthenerd]

Hey guys...
I have been having the same problem for 2 years now. Mine only occurs at idle but it is really irritating for someone with mild OCD like myself. I had my coolant system looked over by Ford and they could not tell me anything useful. I have however found a free fix for this problem at least for me...I turn the dial into the OFF position! There, peace and quite...no more ticking sound every frickin 2 seconds! If its hot, I just turn the AC back on when the driving down the road.

Sean

 

[Papa]

A/C accumulator
I hope this helps, look for oil saturation around the A/C accumulator. My recent experience with my 97X and the short cycling, indicating a slow leak, the first year I added a can of 134. Six months later or so I added a couple more cans. About a week later it was all gone, yes I had tried the dye and kept looking for the tell tail signs of an oil leak usually evident with even the most minute of A/C leaks. Well I found all of the above the last time it gave out; it was the infamous A/C accumulator and the accumulator insulation was saturated with A/C oil. I thought simple replacement until I tried to get the Ford spring; I think it is called, out. I figured out that with a split piece of PVC pipe and a blunt bevel cut into one end I could release the spring enough to slide the fitting out. I got it all back together and the system is working well but I wish I could figure out how to get the spring back into its proper location. Does it fold over a bit or something?

Papa

 

[Eneurb]

A clarification...

The high and low both start at 90

The high goes to 100 and the low goes to 80 after about 1-2 seconds
Then it cycles and starts over. The computer is sending the cycle signal to the relay. We have determined this with a test light.

Thanks for your thoughts…We are stumped and are beginning to think the computer is screwing up...

Ron

The pressures in your A/C system should be very close to the ambient temperature in deg. F. when the system is not operating. When operating, your low side pressures should drop to about 20-25 psi, as your high side should go near 200 psi, or above depending on the ambient temperature. At first I would suspect low refrigerant, but in that case your low side pressure should go down to about 20 psi very quickly, but if it's only going to 80 psi. you may have a problem with your cycle switch (on the accumulator) or the compressor clutch itself. But as for leakage, the first place that I would check is the lower corners of the condensor, incase the pressures were not taken correctly. Since the high side is only going up to 100 psi, I would rule out restriction.