Is there voltage at the connector to the low pressure switch?

Getting late, I'll see what else I can dig up and carry on tomorrow.

 

Check resistance across the high pressure cutout switch (next to the high side service port), the switch should read closed. If it's open, the compressor will not engage.

Fuse 5 in the central junction box provides power to the climate control selector switch, make sure it's good.

Swap the WOT relay in the battery junction box with a known good. If for whatever reason the WOT relay is stuck closed, the PCM thinks the engine is at full throttle and will not allow the compressor to engage.

 

Wow - it was actually that #5 fuse. The fuses were actually one of the first things I checked early on, I must have misssed that one. After all this trouble, turns out to be a blown fuse (15A). I must admit, the AC has seen a lot of work over the week leading up to this blown fuse, I wouldn't think that it would be enough to blow a fuse though. Hmm.

Thanks to everyone who helped me to figure this out, muchas gracias indeed!



Best Regards to All,
Gabriel

 

Hi everyone - i have the same problem except that the high side switch is open and the compressor will not engage. I checked for voltage at the compressor - nothing. #5 fuse is fine. Low side pressure switch does have voltage. Can i jump the high side switch and see if it energizes the compressor? Everything else seems fine.

 

On a 97, yes, you can just jumper the high side switch contacts (Purple & Red/Yellow wires) for troubleshooting purposes.

This circuit is very simple on the 97:

Feed from F5 goes to the selector switch.
Power from the switch (when in one of the proper positions) goes to the P wire at the cutoff switch.
R/Y wire from cutoff switch goes to the cycling switch.
BLACK/Y wire goes from the cycling switch to the high side of the clutch coil.
Low side of the coil is grounded.
There is no provision for WOT control on the 97.
System is monitored for compressor power engagement by the PCM at the output of the cycling switch.

If you have power at the P wire but none at the R/Y wire, the switch is open.

Steve

 

Here's my $.02: see if Auto Zone, Pep Boys, etc are doing "summer tuneups." It may cost $29.95 to "get it tuned-up" and to find out the problem. That's probably less than the Ford house and, more than likely, will be something simple.

As I get older, I realize Inspector Callahan was right: every man has got to know his limitations.

Best of luck.

 

My stuff became intermittant... but I figured out the problem... The issue was that the low side wasn't being allowed to equalize as the pressure came up... this was all linked to rot - yes rot - on the orifice valve (situated inconveniently behind the dash). The pressure would come up, pressure switch would shut down the compressor, and the system would fail.

When the pressure was lower, usually because of ambient issues like the weather, the system would work fine. Pulled the orifice, got a new one from JCWhitney (we can't post prices, but it was pretty cheap), and the system works fine. Had to add a little more to the canister to compensate for what I lost when I was testing (yes, bad me, I know...), but other than that, I can hang meat in the cab of my truck again...

Not sure if this helps... but it's another thing to check...