Just refilled the 134a at about 45lbs. The compressor wouldn't kick on until I hit 45lbs. The compressor clutch kicks on and off, on and off. I don't really know a whole lot about a/c, but as I was fill the a/c dryer tank, as the compressor would kick on, the pressure in the drier tank would drop to 10-15lbs then kick back up to 45 as I was filling. Just wondered if there was some sort of sensor or something else that I could check. The clutch on the compressor kicks on as soon as I turn on the a/c, but kicks right back off and on, over and over.

 

I had the same thing happening when I installed a new a/c compressor recently. I do believe that when it cycles like that it is low on freon. Those little low pressure refill type gagues aren't terribly accurate. I'd try putting a little more in until the clutch stays engaged. Worked for me anyhow. Just don't put so much in that the compressor starts squealing, go a little at a time until the clutch stays engaged.

 

The symptoms that you are describing tells me that the system is working just like it is supposed to and the charge is low. Try this...With the A/C on and the Fan on High (It is really better to charge with a full manifold gauge set but since you said the clutch was cycling and the pressure is returning to a level that turns the clutch back on you should be safe to add more 134.) Continue to add 134 until the clutch will stay engaged long enough for the system to start cooling. At this point you should be able to feel the inlet to the evaporator (smaller aluminum line at the bottom of the A/C case) and get a general idea of the temp. You are fully charged when the outlet of the evaporator (larger aluminum line at the top of the A/C case) is about the same temp as the smaller line at the bottom. If it is very hot/humid at all when you do this the clutch will stop cycling with the fan on high at idle and the upper line as well as the accululator (drier tank looking thing) and the inlet line at the bottom will all be quite cold and sweating. If everything is adjusted correctly you should be able to turn the fan down to low and the clutch will begin cycling off when the low pressure gets down to about 19 to 20 psi. It may take a couple of cans to get it up to working correctly. IF all the safety features are working correctly the system should shut down or worst case the HPRV could blow off some 134 and oil if there is a problem.(condenser airflow or blockage) If the HPRV does open STOP and let a pro look at it. Those safety features are there to prevent the high pressure from getting to a level that one of the hoses would rupture.

 

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I charged my a/c in my 97 Ranger because I noticed it didn't seem to be cooling as well as it had been, and now it will freeze you out of the truck!

I used the gauge setup kit, and had read in my repair manual about both lines feeling about the same temp. Kept checking on the temp of the two lines, and when I felt that they were about the same temp and the gauge had settled down, I stopped. So far, no problems.

 

For those of you that have added Freon to get it to cool again - Where did the missing Freon go??? You must have leaks somewhere. I recommend trying to locate them or you can expet to be adding Freon again shortly.

My experience has been that these Ford AC systems flame out in year 8. Happend to my 96 Explorer (New Compressor and Evaporator Core in 04) and my old 93 F-150 (New Compressor and Evaporator Core in 01). If this trend were to continue, I cshould expect my daughter's 97 Ranger will let go sometime this summer. I hope not, but suspect it will.