Troubleshooting Air Conditioning System

[OVERKILL700HP]

I have a 94 X with an AC problem.
The clutch doesn't spin and blows hot air.
Some background: The compressor and clutch was replaced last summer with a new Ford Unit.
All hoses were replaced, accumulator and orifice was replaced and the system was properly evacuated.
Here's what I did to troubleshoot.

a. Jumped the low pressure switch ( Nothing happened when it was jumped.)
ohms= 15 measured at LP out of circuit

b. Gave 12 volts to the clutch. ( The clutch did turn on at this point )

c. Jumped the high pressure switch ( No change )

d. Put in 1 can of R134 A. (No Change).

e. I replaced the WOT relay. (no change occured).

Any idea what could be wrong?
All information appreciated.

 

[Chew_12]

d. Put in 1 can of R134 A. (No Change).

You have R134A correct? Some of hte early gens came with R12

 

[OVERKILL700HP]

You have converted to R134 A Correct? Most of the trucks came with R12

My 94 came with R134 A

 

[Jason94sport]

All 94's & some 93's had 134. The switch was made mid/end year 93.

 

[exploded99]

I'm not an a/c expert, but when you jump the low side switch that should supply 12 volts to the clutch. But it doesn't. You do know that the clutch works when you hit it with 12 volts.

That circuit also has a temp overlimit switch on it I believe. So I think if you get a wiring diagram and follow thru that circuit you will find where the 12 volts is getting interrupted. I.E. - jump the low side switch, and go to the next point in the circuit, and check for 12 volts incoming.

You night find another post here where the same issue has been discussed that will give you some info on that circuit - sorry I can't be more help on that.

 

[Glacier991]

I'm not at home in CA right now (I'm in my "2nd [childhood] home" of Montana as I write this.) I haven't responded earlier because I do not have access to my manuals, CD's etc and the attendant circuit diagrams and because the advice given by Explored99 was sound. Ah, manuals and wiring diagrams....Those will be important here. You have some good advice above....and you have followed an intelligent troubleshooting path....

Here's my "off the cuff"....The clutch is obviously fine, give it 12V and voila.... so the obvious Q is why isn't it getting 12V when required. I will try in my mind to follow what I think is the circuit path..... In this circuit, you have 12V thru a fuse to the control panel in the cabin. You can energize the AC clutch circuit either by pushing the AC switch, or by selecting defrost on the panel. You then supply a circuit which is the R-12 versions was interrupted by the low pressure cutout and the WOT switches (and an over temperature device of some type which I am not real familiar of the operation of). In a conversion, many times a high pressure cutout was (wisely) added on the high pressure side. THAT I cannot see in my minds eye in this equation because it could be most anywhere.

Without a wiring diagram I'm kinda lost as to wire colors etc, but start by figuring out which fuse it is and checking that... then check for 12V at either end of the terminals.... next go to the control panel switch and by hook or by crook figure a way to test for 12V at the AC switch (if you have it there you will likely have it at the DEFROST switch too) I "think" the next stop is the WOT switch, and then the low pressure cutout.... how the high presure was added and where... well, sorry to say you are on you own. At this point I am less concerned about resistance than the simple presence of 12V +.

The good news is this is not serious, but might be a little frustrating. Just follow the presence of 12V is the best advice, and I hadn't chimed in because it was already wisely given by Explored99 above. Keep us posted... We're happy to continue to add what we can by way of advice...

 

[OVERKILL700HP]

I checked all the fuses and everything looked good.
Incidently, I do have the Ford Explorer Repair CD.
i just took a look at it and it gave some ideas for troubleshooting voltage.
It's describing a circuit 294.


Any idea about this circuits location?

Thanks again guys.

 

[OVERKILL700HP]

I wanted to post an update.
It turned out to be the low pressure switch ( clutch cycling switch ).
Thanks for all your help guys.