compressor won't turn on
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Senior User
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compressor won't turn on
i have a 78 bronco with factory air that i had converted over to 134a, i had my friend do it a few years ago at his shop and he is a cirtified mechanic. but since then he went back into the marines and is in iraq, i don't know if it is a pressure problem or a wiring problem. i have 100psi on the low side without the compressor running, is there a pressure switch that monitors the pressure in the system to make sure there is enough freon before the compressor engages. if so what should the pressure be.
Postmaster
Joined: Jan 2003
Posts: 4,417
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From: Durham, NC
100PSI on the suction side should be enough pressure for the low pressure cutout switch. This switch could be bad,
pull the connector off of it, and measure the resistance. If
it is good, it should measure close to 0 OHMS....
pull the connector off of it, and measure the resistance. If
it is good, it should measure close to 0 OHMS....
Postmaster
Joined: Jan 2003
Posts: 4,417
Likes: 3
From: Durham, NC
The switch should be the same for R-12, or R-134A. Look for a cylindrical shaped device screwed into the refridgerant
line after the capillary tube, entering the heater / evaporator box.
I hope this helps!!!
line after the capillary tube, entering the heater / evaporator box.
I hope this helps!!!
Elder User
Joined: Jun 2003
Posts: 886
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From: Houston/Hope BC
It does not. High pressure = blown hose or clutch. (Clutch failure at about 300PSI)
Low pressure(no gas to move the oil)=ruin the compressor.
Low pressure(no gas to move the oil)=ruin the compressor.
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Elder User
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From: Morgan Hill, CA
I believe that you guys are right that factory air did not use a low pressure cutout that year. To keep the evaporator from freezing, they put a de-icing (thermostat) switch in the evaporator. I don't recall where it is, but look for a couple of wires plugging into the evap. case; one of them should be the same color as the one to the ac clutch (probably black with a yellow stripe irc. Check for power getting there and through that switch.
mike
mike
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i connected the wire from the copressor to the positive on the battery and the clutch engaged and the system got cool. so i know the compresser works but i cant figure out why the compressor won't turn on when i set the control to ac. i did not see any blown fuses. if i cant get it to work can i run a wire from a switch on the dash to turn on the ac since there is no pressure switch in the system anyways.
Elder User
Joined: Jun 2003
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From: Houston/Hope BC
Sure, but you can pretty much guarantee forgeting it and running down the battery, I know I would.
There are only two places I can think of that would cause it not to work, the main panel lever and the de-icing switch; and would bet on the main panel lever switch. I have had mine out but can't remember if it can be dis-assembled for cleaning. GL
There are only two places I can think of that would cause it not to work, the main panel lever and the de-icing switch; and would bet on the main panel lever switch. I have had mine out but can't remember if it can be dis-assembled for cleaning. GL
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if i wire in a sperate switch i would find a wire that was only "hot" when the ignition is on so that way i don't drain the battery, i think the panel lever is wore out because i alwas had to wiggle it to get the compressor to kick on before and now it does not work so i think the contacts are bad. i will try to see if i can clean it or something but with it being a bronco it has the switch for the rear window in it so it may be hard to find a new one for it,
