A/C prob with 87 5.0

fordmustanglx87

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Feb 4, 2006
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Hey all. I bought an A/C test kit to see if my warm air blowing A/C was because it was low. I put it on the compressor and it says its full.. When i turn on my car, and switch it to A/C or Max, it blows warm air, and i dont hear a compressor clicking. I checked the only electronic connector i could find on the compressor and it was clean. I Also checked behind my gauge to see if maybe it came disconnected. Let me know if i have a bad compressor or if something came unplugged. Hopefully this is common.
P.S. No longer R12, converted to 134 a year ago. When i converted it, the A/C worked. Over the next few months last year the air would just stop blowing cold and i didnt hear the compressor. I'd switch it between "vent" and "a/c" multiple times before it would finally catch. But now, that trick no longer works. Please help, Thank you
 
On these, if the system leaks down past a certain pressure, the low pressure switch turns off the clutch, and won't turn it back on.

Electrically, you will have a turn on power signal to the lp switch, but the switch will stay open. If you jumper that wire to ground, the compressor should run.

It means that the charge is low.

Easiest thing is to hook up a can of 134 and try to charge it to at least enough pressure to turn the switch on.
 
WHen the AC is turned on, check the LPS RD mentioned. There should be 12 volts in and out. If you have 12 volts out, go to the WOT relay and check the wiring (it's prone to vulcanizing). If you have 12 volts out of the NC terminal of the WOT relay, check for 12 volts and ground (at the second wire) at the clutch.

Good luck.
 
Here's some diagrams to help you visualize Hissin50's comments. All the A/C related parts are in the lower LH part of the diagram.

Diagram courtesy of Tmoss & Stang&2birds
fuel-alt-links-ign-ac.gif


See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/

http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif
 

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rd said:
Easiest thing is to hook up a can of 134 and try to charge it to at least enough pressure to turn the switch on.

Well, the "easiest" thing to do is to take off the electrical connection at the LPCS and jumper it with something like a paper clip. If the system kicks on, it is electrically working. Leave it on for no more than 60 seconds, If the air gets cold at the vent, this usually means a bad LPCS (check the WOT wires as HISSIN50 mentions for if they are bad, the LPCS gets damaged). Do NOT leave it jumpered for any longer.

If the air did not cool down, most likely the system is low on refrigerant.