A/C has no power - jumped low pressure switch/checked fuses

[speed1972]

Seems the Mustang gods are not shining on me this week. I guess this is the payback I get for leaving my car for a year. Anyway, I've verified that the fuse under the dash is good. Then, I jumped the low pressure switch on the drier and verified (with testing light) that it was jumped properly but I still have no power at the compressor. I have everything apart right now as I'm replacing the drier and liquid line and flushing everything else so but does the car need to be running to get power to the compressor? Where should I be looking next? thanks in advance, Larry

 

[jrichker]

If the fan runs, you have power to the A/C switch. If it des not, then the switch may be bad and that would keep the compressor & fan from working.

Look at the WOT relay located on the strut tower below the mass air meter. The relay & wiring are subject to heat damage.

AutoZone wiring diagrams

http://www.autozone.com/servlet/UiB..._us/0900823d/80/16/71/3c/0900823d8016713c.jsp for 79-88 model Mustangs

http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp for 89-93 model Mustangs

http://www.autozone.com/servlet/UiB..._us/0900823d/80/1d/db/3c/0900823d801ddb3c.jsp for 94-98 model Mustangs

 

[PuterAmI]

does the car need to be running to get power to the compressor?

Yep.

 

[jrichker]

The following diagram is for an 88GT, but the wiring is typical of the models up to 93.

Diagram courtesy of Tmoss & Stang&2birds

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