I have a 2002, 3.0 5 spd manual ranger, the AC will work sometimes, but only on hot days, but not Everytime. I have correct refrigerant, I have jumped the high, and low pressure switch, nothing, I have jumped the compressor clutch, it is fine, and I have also added refrigerant, I'm stumped, I think it could be some type of ambient air temp sensor, but I'm not sure if there is even one on this specific year. Also I checked the relay and fuses, all is good there, I have no clue, can't think of anything else, any help is appreciated!

 

Welcome to the forum

No, there is no ambient temp sensor for the AC

But ambient temp DOES effect Refrigerant pressure, so pressure switches

In 2002 AC is activated by the PCM(engine computer), this is done so if engine temp gets too high(overheating) AC can be shut off, or if you press gas pedal to the floor(WOT, Wide open throttle) the computer will shut off AC for extra power until you back off gas pedal

So how it works
In any setting except OFF and VENT the PCM will get 12volts from the Mode switch and AC Compressor should cycle on and off, every few seconds, this is to dry the air in the cab.
If Mode switch is on AC or MAX AC the compressor should come on full time to cool the air in the cab

What the PCM does
The 2 pressure switches pass a GROUND to the PCM
When AC is activated the PCM passes that GROUND to the Compressor relay which closes and sends 12v to the AC Clutch which engages and causes compressor to spin

Ford always had issues with AC clutch air gap, you can google that, what it means is that the clutch needs to be close enough to the "field" so when the "field has 12volts it can PULL the clutch in and engage the compressor

So what you should do is see if there is 12volts at the compressor clutch wire, use a sew pin to pierce the wire, to see if compressor is disengaging when it has 12volts, or if the 12volts is being cut
If 12volts is there then clutch is the issue
If 12volts is going away then clutch is NOT the issue

Then you should test the Pressure switch wire, find the Black/yellow stripe wire on one of the pressure switches, use same sewing pin to pierce that wire, engine running, see if ground is cutting out when AC compressor is, if so system pressure is getting too low or too high, when its "hot out"

 

I have checked everything with voltmeter and it shows 12 when it initially kicks in then 0 almost imediatley after, 99% of the time it kicks back off, and doesn't turn back on again. When it does decide to work, it will run for around 30 seconds then kick off, I know it's supposed to cycle, but i think it should be closer to the 2 minute mark. I have made a jumper to try to bypass the sensors like you said before, but I put a small peice of wire into the terminals on the plug. Should I puncture the wires and connect hot go ground, or is my method fine?
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Does it seem like the A/C takes forever to start to work, and even when it finally does, it's not very strong?

 

What shows 12v and then 0v??????

 

If the AC works it works really good, but kicks on and off every 30 seconds or so.
the AC clutch shows 12v then 0 when is is not working at all, sometimes it will work 20 minutes into your trip, it does what it feels like
I'm wondering if there is a temp sensor to tell the compressor to kick off, maybe that is bad, and when it gets hot enough it will run, because it lies right on the threshold of working, and not working

 

Essentially I'm saying I have ruled out the clutch, and I'm 99 percent sure the refrigerant is correct.
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No, no temp sensor, EXCEPT for the engine coolant temp(ECT) sensor, turns AC off if engine is over heating

If compressor is losing 12volts then the AC Clutch Relay is opening, and that's controlled by the computer(assuming relay is OK)
So its down to 12volt "Demand" signal from the dash switch
The pressure switch grounds
The computer


This is the wiring diagram, its convoluted which is why I didn't post it before
The purple(violet) wire has 12volts when dash switch selects AC, this goes to computer(demand signal)
The computer then connects pin 69 and 86 together, to Ground the AC Clutch Relay to close it and send 12v to Compressor's clutch to turn it on

You don't have a 2.3l engine so no electric cooling fan
The PCM power relay(and diode) powers the computer and spark and injectors so its fine if engine stays running

 

How do I check that??

 

Check which one?

For the "demand signal" you would open up the PCM wiring and find the Purple wire for pin 41 and stick a sewing needle into it, then start engine, turn on AC and see if that wire stayed at 12volts while AC cycles off

And also see if pins 69 and 86 stay Grounded while AC cycles off

I actually think you should rent a set of pressure gauges to test the system, while the electrical part can have -problems its far more likely for the pressure part to be the problem, yes even with sensors by passed

 

We have a pressure manifold it shows in spec, I would rather go without ac than tear apart PCM lol.

 

Hahaha, we figured it out, it was the engine coolant temp sensor, works perfect now, thank you guys!!!!!

 

Good to hear

But a little perplexed that you didn't have a CEL(check engine light) with a failing ECT sensor, or running issues
Computer would prevent AC from coming on and would also shut it off if ECT sensor showed engine was running HOT, overheating
It would also run the engine richer to cool it down, which should cause running issue if it was NOT running HOT.
It would be a odd way for ECT to fail without setting a code, but obviously did happen in this case

 

It had a check engine, I figured it was a misfire,I it needed plugs and wires so I replaced them, and I forgot, when I got it checked it showed that that sensor was bad so that was what made me replace it

 

OK, so that makes sense

Yes, always good to check for codes even if you think its not related