compressor clutch cycles every few moments

[junker68]

Hi,
I have a 1998 Mountaineer with an A/C problem.
Please excuse me because this is like a foreign language to me.
Simply stated though, when the Max A/C button is pushed the clutch cycles on and off every 7 seconds or so, continuously blowing hot.
When attaching a "Freon pressure indicator" the needle fluctuates as the clutch engages.
When the clutch in unengaged the level rises to 45 indicating adequate pressure, when the clutch engages the pressure drops to 20/25.
Thanks in advance for any thoughts

 

[scdix50]

On most Fords, your need at least 26psi to keep the low pressure switch in a closed to have clutch in-gaged. I try to keep low side pressure at 30-35 psi at idle. Do have a full set of gages (low side & high side w/ a fill line).

 

[shadowless127]

You are most likely low on refrigerant with the possibility of a leak in the system somewhere. I'm in the same boat.

 

[junker68]

Thanks all.

No, I just have the cheap refrigerant you buy at the local auto parts store.

 

[ranger7ltr]

Recommend finding a friend with a proper set of gauges...

You need to measure the high and the low side as well...The pressures on the low side will tell how well or how long the low pressure switch stays engaged but the high side will tell you what condition the refrigerant system is in...

System pressures are absolutely dependent on ambient temperature as well...The air temp around the vehicles' a/c system times 2.3-2.7 is where the high side pressures should be...If you are using the freon can with the the low side gauge you are not able to determine what amount of R-134a needs to be installed in the system...

Actually R-134a SHOULD be measured by total system volume weight and yet most people add refrigerant to the system to stabilize the compressor clutch cycling...Using the low side pressures only can cause an overfill condition and cause more issues down the line...

When the clutch engages the system refrigerant is flowing throughout the system and you are measuring the actual low side pressures... When the clutch disengages, the system goes to a static situation and the pressure measurement will increase and cause the low pressure switch to re-engage...And this is why your clutch is quick cycling....

 

[junker68]

Ranger, thanks so much for the explanation!

 

[SoNic67]

You are low on Refrigerant. Possibly you will loose the one that you plan add too, it is just a waste of money. First you have to find the leaking place and fix it.

Most of the time is at the compressor shaft seal, and that means rebuilding the A/C system. Another place is a pinhole in the A/C condenser (front of engine radiator).

 

[masospaghetti]

When the clutch in unengaged the level rises to 45 indicating adequate pressure, when the clutch engages the pressure drops to 20/25.
Thanks in advance for any thoughts

45 psi when the system is off indicates low refrigerant. The exact correct number varies with temperature, but it should be between 70-100 psi. Of course, the correct way to charge an air conditioner is by weight, but if you can't do that, you could add refrigerant until the vent temperatures bottom out. Use a little thermometer you stick in the dash vent. This will get you close to the correct charge.

But, refrigerant is not consumed. If you are low on refrigerant then you have a leak somewhere. Best bet is to get a UV dye and add it while you still have some pressure in there, the dye will show you where the leak is.

 

[junker68]

Thanks!

 

[4rd Xplora]

You are most likely low on refrigerant with the possibility of a leak in the system somewhere. I'm in the same boat.

Same here. Had a can of that "self charge" freon and charged the system per instructions. I replaced the compressor, oriface tube and the accumulator a couple of years back. If it goes flat within a month or so, I'll fix it. If it takes another couple of years......

 

[bill06447]

if you have the original foam-wrapped accumulator, it most likely rusty and porous. UV dye is a must, and you don't need a fancy light, just a black light from Walmart in a drop light or (like I did) in a desk lamp...showed the whole accumulator glowing from that dam foam, the replacement won't have it

Bill

 

[masospaghetti]

Just FYI, the service ports on the A/C are common causes of leaks.

 

[koda2000]

I had a leak in an old Pontiac. I could charge the system in the spring and it would be fine until the following spring. I once tried a product that was guaranteed to seal a leak. It worked so well I had to replace the accumulator! While I had the system open I replaced all the O-rings and it was fine after that. Using dye is the best way to locate a leak.