I just bought a 99 ranger 3.0L auto The previous owner has removed the AC relay in PDB and installed a jumper switch. Ran the wires into the cab with a switch. To turn on the AC you flipped the toggle switch. Does not matter what position the the selector switch is. Flip the switch and the compressor kicks in. You do have to move the selector switch from off to get the blower to work. If you select max air the blower increases. If you flip the toggle switch all works great cold air. I ran if for a couple of hours no problem.

With fingers crossed I pulled the jumper and put a relay back in no luck. I would like it to work like it should.
Bottom line if you jump the ac relay all is fine. Other than that the switch works normal. (Air directs to floor, defrost, etc)


Could it be the switch? How could I test without just buying a switch?

 

Start by verifying Fuses #10 (7.5 amp in Dash IP) and Mini Fuse #1 (10 amp in PDB under hood) are not blown. If both fuses are good, pull any jumper connections at the AC relay socket. With the Key on (run position), back probe terminals #3 and #2 of the AC Relay socket with a voltmeter or test light to chassis ground. These two terminal should be hot (power).

 

Sorry its been so long, weather and work I have not been able to get back to it.

The fuses were both good. I was not sure which terminal was 2 or 3 so I drew a diagram to be sure. it shows which 2 terminals I had power to. The others did not have power. The dotted lines shows where the jumper switch was located.

Flip the switch and the ac works and blows cold. I assumes that rules out the pressure switches.

Could it be the WOT?

Thanks

 

First I gotta ask, are you sure the relay you used was new from Ford or is known working relay?

No, the jumper is supplying power directly to the AC Compressor, bypassing the control switch's input to the PCM.

Test the pressure switch's as follows:

Pull the electrical connector at the Low Pressure Cycling Switch. Using a volt ohm meter check for continuity between the switch’s two terminals. You should read continuity. If not replace switch.

Next, check for continuity between the switch’s electrical connector terminal the Red with Yellow stripe wire and chassis ground. If it reads as open circuit either the High Pressure Cut Off Switch or its associated ground is bad.

If the above checks good, pull Mini Fuse #1 (10 amp in PDB under hood) and see if you still have power at the relay socket terminal in your sketch labeled “Jumper”. If you lose power with the fuse removed it is terminal 3.

The other terminal of your sketch labeled “AC” should be terminal 4. You can confirm this by checking with a volt ohm meter for continuity between this terminal and the A/C Compressor’s electrical connector terminal Gray with White stripe wire.

The other terminal you found power at should be terminal 2 from the PCM Power Relay. With the Key On, using a volt ohm meter, you can verify this by pulling Mini Fuse #8 (30 amp in PDB under hood) and see if you lose power at that terminal.

I believe if you look down inside the remaining two terminals with a flash light, one my be blank (no actual wire connected). The other with a wired terminal should be terminal 1.

Once you’ve identified the above, turn the key off and disconnect the battery, then the PCM connector. Reconnect the battery, then locate a purple wire at the PCM wire connector (PCM terminal # 41), a Pink with Yellow stripe wire (PCM terminal # 69), and a Black with Yellow stripe wire (PCM terminal # 86).

With the Key on and the selector control set to A/C, check for power at the purple wire in the PCM wiring connector. If power is present, proceed to next test.

Check for continuity between the Black with Yellow stripe wire at the PCM wire connector and the same color wire at the A/C low pressure cycling switch connector. If you have continuity proceed to next test.

With the Key Off, check for continuity between the Pink with Yellow stripe wire at the PCM connector and terminal 1 of the A/C Relay socket.

If all of the above checks good, the problem more than likely lies within the PCM itself.

 

I will run the tests, but to answer your question I did not try a new relay. I moved a couple from other slots in the PDB. I'm going to go buy a new one because I have to have it anyway because it was missing when I bought the truck.

I'm assuming it is more than the relay (maybe a bad assumption) thinking the previous owner at least tried the relay before going to all the trouble of running a jumper switch in to the cab.

Not knowing what was done I just need to take your test procedures and run through the whole thing.

Thanks for the comprehensive testing procedures. It may take me a little time to get through them but I will.

 

Thanks Rev I solved it. Bad low pressure switch.

Put new relay in compressor cycled and I knew I was on the right track.

Check continuity on low switch connector, good, so coming from high switch good.

Check continuity on low switch, none.

Jump switch ran like a charm.

Installed new switch runs like a charm.

Thanks for all your help

 

No problem, glad to hear it was a simple fix.

 

I guess I jinks it. It back to cycling. New relay and new low pressure switch. I put a gauge on it and it shows about 10 lbs of pressure obviously low. I bought some leak detector. It got to be leaking somewhere. At $7.00 bucks a can I'm trying to not to waste $25 or $30 of freon.

The most confusing part is that is blows cold air.

 

Depending on how long its been since the system was last serviced, it might just be normal leak down. I have to top mine off about every third year or so of normal use.