1994 Ford F-150 AC compressor won't run

Tiny
SAURD
  • MEMBER
  • 1994 FORD F-150
  • V8
  • 4WD
  • AUTOMATIC
  • 142,000 MILES
I have a 1994 Ford F-150 4x4 step side. The AC does not work. Figured it needed a charge of R-134, but in order to add you need to get the compressor to run. First thought was to jump the wires at the sensor located on the dryer, which I had been told was the right place to do so. Still no compressor. I then hotwired the compressor right to the battery and the clutch engaged as it should. I then started the truck and engaged the compressor to see if the R-134 did indeed need to be charged, the air produced by the system was cold, so I have concluded I do not need to add any R-134.

The major question at this point is why the compressor won’t engage as it should. I check the fuse and there is power at the fuse when the compressor should be on. I check this with a meter. My question is where to look next? Do these dash switches go bad? If so how to I verify? Is the fuse under the dash before or after the switch in the circuit? If before, the switch is probably working. If not it could be the switch. A wiring diagram would be helpful, any ideas where to get one that would include the AC system? Haynes doesn’t as far as I can see.

In general any ideas on where to go next?

Thanks,
saurd
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Sunday, April 27th, 2008 AT 10:45 PM

2 Replies

Tiny
MHPAUTOS
  • EXPERT
Hi there,

you really need to get the pressures checked in the system, there are safety cut out switches for high and low pressure (normally) that will shut the A/C down if there is an internal problem, so a pressure test should be carried out first, the tech will then be able to advise you on the next step you need to take.

Mark (mhpautos)
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Monday, April 28th, 2008 AT 4:07 AM
Tiny
BOBBYCOOK
  • MEMBER
By jumping the senosor, you may have already verified you do have a switch problem. If you want to check things out, the basic procedure would be as follows.

To verify if you have a switch problem, with the ignition on and the ac switch on, check for 12 volts on both sides of the sensor coming from th dryer (low pressure). If you have volltage on both isides of the sensor, find th high side sensor and check for voltage on both sides also. If you do not have 12 volts on both siies of the the sensor, the high sensor may be bad. If yiu have 12v on both sides of the sensor, find the relay box and the comprssor relay.(Its location should be noted on the cover). This coil should click each time you turn the ac of and on, If it does not than you have a bad relay. If you do not have v12V at the low pressure sensor than, you could have a bad switch. Or climate control problem. The basic circuit from the switch is low sneonsor high sensor realy compressor. You will also have a control voltage to the coils from the temp contril
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Friday, June 6th, 2008 AT 8:34 PM

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