Hi,

I have a 1997 F150 XLT 4X4 4.6
When the air conditioner is turned on it will work for awhile (Maybe 10-15 min) then will kick out. Puts out the same temp as if it were on the vent selection. It might kick back on in 20 min and can take up to 45 min. It seems if the truck is shut off for awhile and restarted, the air will be working again but only for a short time. I had the system drained, reoiled and recharged. I thought it was fixed but then it started again. When it works the air is perfectly cold. When the air kicks out I checked under the hood and the compressor is not engaged. Is there a switch for the compressor that may be bad? Any feedback and help would be appreciated.

Thanks

 

Whomever re-filled the A/C system needs to check it again. What you are describing is a low refrigerent condition and the compressor is shutting itself off to protect it.

Or if it is not really hot outside the A/C will cycle on and off at strange times. Try and run it on MAX the compressor should run the whole time. If it shuts off in MAX you probably have the condition listed above.

 

The symptom of cycling like that are either low charge or a bad cycle switch. If you just had the system redone and know there are no leaks, you have an electrical problem. The cycle switch is on the accumulator drier and has a two-wire plug attached. If you unplug the switch and jump the two terminals in the harness, the compressor clutch should kick on and stay on. If the A/C cools properly with the switch jumped, replace the cycle swicth. If not, look elsewhere. If the clutch does not engage when the switch is jumped, you have a bad field or worn out clutch, or a broken wire somewhere. Also, be sure you have power to the cycle switch.



UFM82

 

Hi,
Please don't take this the wrong way but when you said it was drained and reoiled I wonder just what the shop did. The cycling switch and the other recs. made would sure make the symptoms you described. I would first like to know if the shop evacuated the system, Put a vaccum pump on it for at least 30 minutes, then recharged it. I think it sounds a little like a moisture problem in the gas. Freon will collect moisture ( that is why they put a dryer in the system) and the moisture will freeze up the evaporator after the system gets down to temp. Obviously with the evap. frozen up the system stops working until the moisture unfreezes (I think thats a word???) After the moisture loosens up the whole cycle starts over. Sounds like you need to revisit the A?C shop and ask questions. Hope this helps

 

Your symptoms are NOT of a low charge or a cycling switch problem. If it were, the compressor clutch would short-cycle or the air would not be cold. This symptom only occurs after the system has been in operation for a period of time.

You have one of several problems, listed in order of likelyhood:

1) Clutch. Next time it stops working, bang it with a piece of a broomstick and see if the clutch hub pulls in. If it does, adjust the air gap or replace the clutch.

2) Evaporator freeze-up. This is normally accompanied by an odorless fog from the vents and a reduction of airflow. A visual inspection of the accumulator and associated tubing will show very heavy frosting, especially in very humid weather conditions.

3) Overcharge/over pressure. If the system is overcharged or there is a problem in the system that causes the system to overpressurize, the clutch will be cut off untill the pressure drops below the cut-in threshold. A failure of the cooling fan, for example, can cause an overpressure condition. A restriction in the lines is another possibility.

4) Electrical problem in the control circuit.

Good luck, try the broomstick first. This is a very common occurance on the older SHOs.

Steve

 

Thanks for all the feedback. Very helpfull.
I pulled the clutch off and removed one shim to tighten the air gap. Has been working ever since.
Thanks again.