A/C Gurus...Need Help Please

[rc1626]

A/C stopped working on my 99 5.0 Explorer about a month ago. Compressor stopped engaging. I wound up replacing the compressor clutch and now after reading a little feel I probably didn't have to. I read somewhere to back probe the compressor clutch connector directly off the battery to see if the clutch will engage. Sure enough I was able to get it to engage(cycle).

Compressor clutch connector measures 13.5 volts when disconnected from the clutch and A/C on. But when I connect the connector and back probe the connector the voltage drops to zero.

Any ideas of what might be causing this? Pressure switches, relays??? I'm at a loss and any help would be appreciated.

Thanks.
Rob

 

[rc1626]

One other thing to add is that w/ the guages hooked up and compressor kicked on the low side is reading about 32-33psi while the high side is 145-150psi. When the compressor is cycled off the pressures rise considerably. I don't know if this helps but thought it might be worth adding.
Thanks.
Rob

 

[rhauf]

maybe the system just needs a charge up?? also, it's possible that you're low pressure cycling switch (mounted to the accumulator) is bad.. i had to replace mine once.. but those rarely fail

 

[rc1626]

Thanks rhauf,
I don't think it needs a charge as numbers w/ compressor engaged are pretty close to within normal limits. High side is a little low but very close to normal range. As for a low pressure switch, that might be something to look at. Is there a high pressure switch that works in conjuction with the cycling of the compressor? The reason why I ask is that when I manually cycle the compressor the psi numbers are close to normal but when I disconnect battery power to the compressor and the compressor is not able to cycle pressures rise very quickly and get high.
Any thoughts......anyone?
Thanks.
Rob

 

[my98nnj]

Your pressures seem fine. The low and high side will equal out when the system is idle. Items to check would be the compressor relay and the pressure switches. Perhaps somebody on here can point you to an electrical diagram?

Follow all the A/C lines, you should find the switches for hi and low. Simply check resistance across them, it should be zero as in closed circuit. If you come across one thats open, it's faulty.

An evacuation and recharge will be necessary to change them if that's the case.

 

[Maniak]

I don't know about the 2nd gens, but on the 1st gen the low pressure switch is actually connected via a shrader valve. You call pull the switch and then put a new one on without loosing much (if any) gas.

~Mark

 

[safn1949]

That's always been the case with the A/C systems I have worked on.Simply unscrew it and screw the new one on and you only loose a puff of refrigerant.

 

[rc1626]

You guys have been great.
my98nnj,
It sounds like my 0 voltage on the clutch connector when plugged in means it's a closed circuit and ok. Not an electrical person but always looking to learn.

Do any of you know what actually engages the clutch? As I had wrote earlier, I'm getting 13.5 volts at the clutch connector unplugged. If the voltage is there what would stop the clutch from engaging. If a switch or relay is the culprit how would it cause the clutch to not engage even when proper voltage is present?

One last thing. Where would I find the compressor clutch relay? I'm assuming under the hood, driver's side by the brake booster in the relay/fuse box? Anyone know which one?

Thanks again.
Rob

 

[rc1626]

Well, it's fixed. Not the clutch or the the relay or the pressure switches.

Nope, none of the above. After trying out the above mentioned parts from my wifes 01 explorer and nothing working I started playing with the wiring. Turned out upon fooling with the wiring of the compressor clutch I got it to engage and cycle. Pulled the wires out of their loom for inspection and sure enough I found a break at one point where the wire was severely bent. Spliced it and now we are good to go......ahh cold air again! Sometimes these things just aren't what you'd think they'd be. Just takes some time and patience.
Thanks again everyone.
Rob

 

[safn1949]

Well, it's fixed. Not the clutch or the the relay or the pressure switches.

Nope, none of the above. After trying out the above mentioned parts from my wifes 01 explorer and nothing working I started playing with the wiring. Turned out upon fooling with the wiring of the compressor clutch I got it to engage and cycle. Pulled the wires out of their loom for inspection and sure enough I found a break at one point where the wire was severely bent. Spliced it and now we are good to go......ahh cold air again! Sometimes these things just aren't what you'd think they'd be. Just takes some time and patience.
Thanks again everyone.
Rob

Good job,that's exactly why I tell these guys to find the problem first instead of throwing parts and money at it.Cost you $0 bucks to fix,just a little time.