2002 Explorer AC compressor will not engage.

[dvdswan]

Got home from a trip for work and the wife tells me the AC on the Explorer isn't blowing cold. Sure enough just blows warm air. AC button light turns on, check what I though was the fuse and relay for the AC and both were fine (according to a YouTube video). The compressor does not engage. I checked for power to the compressor and got NO light from the test light on either wire. Test light is good and checked on the battery.

AC was working when I left on Monday. I don't know if there was a loss of freon if the AC button light would come on or not.

Is there a diagram that show what each relay and fuse are? Or suggestions? 2002 Explorer 4.0L 4WD auto.

 

[Uncle Gump]

I would try jumping the low pressure cut off switch. If the compressor starts... it's low on refrigerant.

 

[franklin2]

Here's an overview of the system.

 

[dvdswan]

I believe I found the low pressure switch, it was on the inside of the core support by on the condenser. Compressor did not engage. It was a round 4-plug connector with 2 wires in it.

 

[Uncle Gump]

I believe I found the low pressure switch, it was on the inside of the core support by on the condenser. Compressor did not engage. It was a round 4-plug connector with 2 wires in it.

That sounds like a high pressure cut out switch. Low pressure switch is typically on the accumulator or on a low side hose.

Those hoses up on the core support are most likely high pressure.

 

[dvdswan]

Found the low pressure switch, jumped it and the compressor kicks on. I guess that's good news. So now I either have an o-ring, line leaking, or the switch is bad. Is that correct? I ohmed the switch and got infinite ohms with the engine and key off. Assuming that's what I should see, since if it was shorted the compressor would be on constantly.

Since I don't have any ac pressure gauges, I guess I'll have to take it in and pay the diag and repair.

 

[sgtsandman]

Since I don't have any ac pressure gauges, I guess I'll have to take it in and pay the diag and repair.

I think that would be the best bet. They have the equipment to do leak tests and what not that the typical person doesn't have. Having to pay the shop rate stinks but there are times when one just has to do it.

 

[RobbieD]

A good, honest shop would be your best option.

Kudos on your troubleshooting it. At least you now know, going into a repair shop, that it's most likely just a leaked-down system, and that the compressor appears to be OK.

I would be looking at the shop first doing a visual on the AC system (in some cases a leak point leaves a tell-tell stain of refrigerant oil), and then pull a vacuum and see if it holds. If it doesn't hold the leak will have to be located and repaired. If a vacuum holds, it can be recharged, with UV leak-detect dye added.

At least, you're not going in blind and clueless.

 

[Uncle Gump]

I agree with @RobbieD ... a complete visual inspection usually will identify where the leak is with a bit of oil residue.

My truck takes a can about every third year. I've leak tested (visual and electronic) and can't find the leak. Probably not the best solution but I figure if I can't find the leak I'm not just throwing expensive A/C parts at it in an attempt to fix the leak. One of these days I'm certain the leak will get worse and I'll find it and fix it.

 

[RobbieD]

My truck takes a can about every third year. I've leak tested (visual and electronic) and can't find the leak. Probably not the best solution but I figure if I can't find the leak I'm not just throwing expensive A/C parts at it in an attempt to fix the leak. One of these days I'm certain the leak will get worse and I'll find it and fix it.

That's actually a good approach, in my opinion. If it's cost-effective to keep an AC system working acceptably for a few more years, at some point a component will fail, requiring replacement. Once an older system HAS to be opened to have one component replaced (with which a new accumulator/drier is also recommended), I'd rather replace everything at once. Exceptions may be the hard parts, the evaporator and condenser, but that case would include R&R for flushing, inspection, and cleaning and straightening any bent fins.

Basically, "restore by replacing" the entire refrigerant part of the system, and start with everything new. Only replacing one failed component with new is not a guarantee that another different old component won't fail soon after, and labor time and recharges do add up.

And on an older R12 truck it makes all the more sense to just replace everything, and start with all new parts.

The big drawback, is that these days parts are much more expensive, and quality has really gone downhill.