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2000 Ford F150 a/c not working

Patient50 on Wed July 21, 2010 1:04 PM User is offline

Year: 2000
Make: Ford
Model: F150
Engine Size: 4.2l V-6
Refrigerant Type: R134a
Ambient Temp: 74 deg F
Pressure Low: 35-50
Pressure High: 110-140
Country of Origin: United States

I'm a beginner, trying to figure out what I need to do to make the a/c work in my truck. Thanks in advance for any help.

I've owned the truck for 2 years. It has app. 150,000 miles and the air didn't work when I bought it. Last year, when I knew even less than now, I used a friends hose and single gage and it said it needed refrigerant. So in went a can (or two - I seem to remember needing to cycle the compressor using a jumper). It cooled some, but not enough to make me think things were okay. So, I bought a set of gages from Autozone and checked the pressures. I vaguely remember that the high pressure seemed too high at the time, though I can't find my notes from working on it back then. I do remember reading that the high pressure may indicate a plugged orifice. I decided to not run the air until I learned more about a/c systems.

So here I am, a year later, knowing more, but still not enough.

I checked pressures again last night, and they’re listed above. I don't think the high pressure was as high as it was last year. A thermometer in the duct went from 90 deg F down to 86 deg F – the truck had been sitting in the sun all day, and it was still warm inside when I worked on it in the evening.

Some other observations:

The compressor turns on every 5 seconds or so, and is only on for about 1 second. Is that working correctly?

I checked the fan clutch by using a tachometer – the engine was turning 820 rpm, the water pump was turning 1125 rpm, and the fan blade was turning at 1075 rpm. The fan blade slowed down several times to about 900 rpm and then sped back up to 1075, where it stayed as the engine got up to temperature. It seems that the fan clutch is working okay.

I misted water onto the condenser using the garden hose - it didn't seem to change anything.

- The discharge line from the compressor to the top of the condenser is warm/hot, which I read is what it should be.
- The liquid line from the bottom of the condenser to the evaporator is cool/cold and wet with humidity. I read that this should be warm, so there must be an issue here.
- The suction line coming out of the evaporator is “room temperature” – not hot or cold. I read that it should be cold, so there must be an issue here as well. The accumulator and the hose from the accumulator to the compressor are “room temperature” also.

So, with all that said, I’m trying to determine what to do next – any ideas? Thanks!

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