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compressor cycles on/off rapidly

Bel-Air on Sat May 24, 2014 5:27 PM User is offlineView users profile

Year: 1997
Make: Ford
Model: F150
Engine Size: 4.2 v6
Refrigerant Type: r134
Ambient Temp: 77
Pressure Low: 30-40
Pressure High: 140
Country of Origin: United States

Noticed last week that the ac was blowing cool, not cold, and I could hear clicking at idle. Raised the hood and I could see the compressor cycling on/off about 1 time per second. After couple of googles I decided since I have a vacuum pump and manifold I would pull it down and put a charge on it. Step by step -

- Hooked up hoses, when I started vacuum I saw a lot more dye than I'm used to seeing on a low system (I have a van I have to charge every year)
- Took vacuum about 2 minutes to get to the peg, let it run about 10 minutes.
- Started truck, added 12oz freon, 3 oz oil, on the 2nd 12oz can of freon the compressor started cycling on/off again. As the can went in it started cycling faster.
- Checked vents, blowing cool not cold.
- Sticker under hood says 2lbs so I tried to estimate the 3rd can, i let it go for about 3-4 minutes, the system did not seem to be taking any more. Compressor ran for about 5 seconds after I stopped and started the engine, then started cycling rapidly again.

I tried to post a pic of the gauges, not sure if it's coming up or not. The low side is sitting on 38 and the high side is 140, needles are jumping with the compressor clicks.

I'm lost at this point. You guys think I still have a freon level issue ? Or should I just take it in ? Thanks, glad this forum is here.

mk378 on Sat May 24, 2014 6:07 PM User is offline

While you had it empty, you should have checked the OT. Also if the high side port is downstream of the HPCO switch, it could be cycling on HPCO but you don't see it on the gauge because there is a blockage such as the condenser.

The low side should go down to about 25 before the compressor turns off. If not, the switch could be bad and turning it off too soon.

How cold does the accumulator get? You may actually have proper refrigeration performance but reheating from the heater core. There should be some cycling at only 77 ambient.

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