I have an '890 F250 with 460 Engine. When I go to turn on the AC, the compressor never turns on. The rest of the Heating/ventilation system works fine, so I think the Fuse for the system is OK. When I measure the voltage on the compressor plug it goes from about 0.007V with the AC off to about 0.05 Volts with it on. I kbow there is a diode in the system, but I used my Fluke meter across it and it reads about 0.6V like a diode should.

If I were to put 12V across the pins of the compressor with the engine running should the compressor kick in, or does it not take 12V directly?

Any words of wisdom would be greatly appreciated.

 

Most likely your AC pressure switch is malfunctioning or there is actually low pressure int he system, thus keeping the compressor from activiating.

To test this quickly jumper the 2-pin plug on the accumulator (near the blower motor) if you jumper it and the compressor comes on then you know either the low-pressure switch is at fault or your AC system has lost its refrigerant.

ALSO: DO NOT JUMPER THE PINS FOR MORE THEN A SECOND OR TWO, JUST ENOUGHT TIME TO SEE IF THE CLUTCH ENGAUES.

 

Thanks, I will go try that. If it does end up being low pressure in the system, am I going to be better off trying to get it recharged with R-12 (Can you even still do this) or getting the system converted to R134A?

Thanks

 

I think you will find that converting to 134A is really the only sane option. Get it done by a proper AC outfit and you should be fine. It may cost a little more but in the end its a great selling feature for the truck and will make it a hell of a lot easier should you need to recharge in the future.

 

You can test the compressor by jumping the switch with the ignition on and engine off. You can see and hear the compressor clutch kick in. You can either convert to r134a or if you can find someone who sells it, there is a direct replacement for r12 called freeze 12. I think the Bumper to Bumper stores around here sell it. For some reason, not too many people know about it. I know it exist, because my brother has some at his house.

 

I just bouht some Freeze 12 and all associated oil/stop leak plus necessary hardware for about $50. Barring no major leaks, I should be back up in a jiffy. Thanks for the advice.

 

Glad I could help