[Cobra Jet]

Toshi -

Pull the harness connector off of the A/C pressure switch (you'll find it at the firewall, passenger side, on top of a black (original color) canister (silver if a replacement canister). Once you pull the connector off the switch, get a paper clip, open it, bend it to form a "U", then insert each end of the "U" into the harness connector's female sockets. Now, start the vehicle, put the air to MAX A/C and w/ the vehicle in park (or neutral w/ ebrake on for a manual), see if you can see the clutch on the A/C compressor turn on and it should be cycling (you should also hear a distinct "click" when the compressor turns on). If by jumping the switch the A/C kicks on (air is getting cold) and the compressor cycles over (clutch activates at normal intervals), then your problem is the A/C pressure switch.

To replace the switch, just twist it off of the canister (it should not be installed super tight). A new switch is around $20 +/- at any of the common Auto Parts stores and you install the new in the reverse manner. Super easy, less than a 10 minute "job".


Now - if when jumpering the A/C pressure switch connector your A/C compressor cycles sporadically, or I should say, it keeps turning on then off rather quickly, then the A/C system is low on freon. You would then have to check for leaks, because adding new freon would be waste if you can't find the source of the leak.


The A/C pressure switch is the most common point of failure within an A/C system, especially on the Mustang 5.0's (also prior F-Series and Broncos). It's a cheap part than can be easily diagnosed. Sometimes they can be bad right out of the box too.

Best of luck!