A/C clutch will not engage, freon full

[Heuster]

97 Mercury Mountaineer - 5.0

I need some help with an A/C issue - my wife was driving with COLD a/c and all of the sudden it just went hot. Yes, I have a broken blend door that I have duct taped in place...I checked that, it's not the problem.

The a/c clutch simply won't engage...I tried to jump the low pressure switch and then turn the car on with the a/c on and the clutch did not engage. I replaced the low pressure switch about a year ago.

I tried to move some of the relays in the fuse panel under the hood...there are three of them that are identical so I swapped them to see if one of them might have gone out...nothing (I didn't do this with the low pressure switch jumped though) I'm not sure which one does what under there...any help? None of the fuses look blown. I also checked the fuse panel on the driver door facing side of the dash and everything there looks good too.

I live in AZ....it's going to be 115 tomorrow - any ideas or help would be really, really great.

 

[TheJackal]

have you tried testing the compressor clutch harness to see if power is going that way?

If power's there but the clutch isn't engaging, then the clutch is bad.

Could also be high pressure switch or WOT cut-out relay (if there is one)

 

[Heuster]

How do I test for either of these? I have no idea...I don't have any electronic testing gear, but I can "jumper" things I gotta have the raw, down and dirty solutions, cause my garage isn't full of a bunch of tools.

retry - I jumped the low pressure switch again and the a/c clutch came on. Is it the low pressure switch then?

Adding picture:
I jumped the end with the red arrow
I replaced the one with the green arrow about 1 year ago with a checker replacement part.

 

[Heuster]

*bump*

 

[Heuster]

Still need some help on this gents.

 

[my98nnj]

How do you know the system is charged correctly with R134?
Low pressure switch could be doing it's job, cutting out the system because there is a problem.

You need a set of gauges to see what's really going on with the system. The condensor could have let go and your charge simple escaped. That very well could have happened while it was running, working fine on minute, gone the next.

Don't over look the obvious.

 

[Cobraguy]

What is the system static pressure? Any signs of oil spray anywhere? Let's see if you really do have a full charge.

There may be another pressure switch on the driver's side of the condensor...below the high side port...depending on model. If it's disconnected, the clutch won't engage.

Get your test light and see if there is power to the clutch connector. Check for proper ground. If you have power there, the clutch is bad if it won't engage.

The good news is it should only be 112 today. The bad news is it's going to be humid...

 

[Heuster]

Well - the low pressure switch went bad again. I replaced it and everything is working correctly. Aftermarket parts...

Thank you for all of your input.