NEW A/C, COMPRESSOR WONT ENGAGE!

[IsaacJB97]

Hi all! I spent all day today putting on a new compressor, accumulator, orifice tube, low side pressure switch, and relay. Of course, I flushed the hell out of the system with a half gallon of solvent through a flush gun, then shop air, then flush gun. Installed the new parts, pulled a vacuum for an hour, and let the system hold a vacuum for an hour. No leaks. I cranked the motor, tapped a can of refrigerant, and the system pulled in about 3/4 of the can then stopped pulling. Low side gauge read 85lbs and High Side read 50. The clutch never engaged so I closed the can, and shut her down for the night. What I’m the heck is going on!? Thanks for the help!!!

 

[Collin Whitfield]

To make sure it's not just the low pressure switch, unplug it and jump the two holes in the harness with a paperclip. That should turn the A/C clutch on if everything else is connected correctly.

 

[shucker1]

You could also check for damaged or broken compressor clutch control wires.

Perhaps they were on their last leg of just got damaged during your change out of the A\C Compressor.

I hate to ask a stupid question but "Did you reconnect the compressor clutch wires"?

 

[boominXplorer]

What size can did you use? The stagnant pressures at 70 degrees should be around 75 on both sides.

 

[IsaacJB97]

What size can did you use? The stagnant pressures at 70 degrees should be around 75 on both sides.

One 12oz can. They system only took about 9oz and low side was reading 85.

 

[IsaacJB97]

To make sure it's not just the low pressure switch, unplug it and jump the two holes in the harness with a paperclip. That should turn the A/C clutch on if everything else is connected correctly.

Well, I put a new one on. I did jump from the relay and the clutch engaged but the relay is brand new too.

 

[IsaacJB97]

You could also check for damaged or broken compressor clutch control wires.

Perhaps they were on their last leg of just got damaged during your change out of the A\C Compressor.

I hate to ask a stupid question but "Did you reconnect the compressor clutch wires"?

That could be the ticket! The harness clip thing was pretty dirty from a previous power steering fluid leak that spewed fluid everywhere. I cleaned it all up with contact cleaner but, if it was the wires, wouldn’t that have stopped the clutch from engaging when I jumped it from the relay?

 

[shucker1]

Yes Sir.

In short description.

Low Pressure switch is Normally Open with pressure less than 25 PSI. It keeps the compressor from drawing a Vacuum on the system which is not good for the compressor.

Above 25 PSI switch goes closed and provides a path to ground.

Switch controls the coil of the relay.

We don't want all of that current flowing through a little switch, thus the relay.

IF>>>> Clutch Coil wires are damaged Then >>> clutch cannot get command signal to engage.

The system may also employ a "Fly Back Diode" since our clutch is magnetic this diode prevents excess voltage spikes from getting to the computer which could short out it's little old brain.

Older Explorers (Gen 1) also employed a WOT (Wide Open Throttle) cutout. It disabled control circuit during WOT condition to free up additional Horse Power.

 

[IsaacJB97]

Yes Sir.

In short description.

Low Pressure switch is Normally Open with pressure less than 25 PSI. It keeps the compressor from drawing a Vacuum on the system which is not good for the compressor.

Above 25 PSI switch goes closed and provides a path to ground.

Switch controls the coil of the relay.

We don't want all of that current flowing through a little switch, thus the relay.

IF>>>> Clutch Coil wires are damaged Then >>> clutch cannot get command signal to engage.

The system may also employ a "Fly Back Diode" since our clutch is magnetic this diode prevents excess voltage spikes from getting to the computer which could short out it's little old brain.

Older Explorers (Gen 1) also employed a WOT (Wide Open Throttle) cutout. It disabled control circuit during WOT condition to free up additional Horse Power.

So what you’re saying is, despite the fact that I jumped it from the wide open throttle relay and the clutch engaged, my problem could still be with the compressor control wires? The same wire cluster that plug into the top of the compressor? Ok I’ll replace and go from there!

 

[IsaacJB97]

While I’m at the parts house I’ll just buy a new diode and another freakin low pressure switch. Just in case.

 

[boominXplorer]

One 12oz can. They system only took about 9oz and low side was reading 85.

I don't have the specs handy but I swear it takes well over a pound of r134a (16oz). I think you just didn't put enough in if everything checks out and you can jump it at the switch. You pulled vacuum and added the refrigerant while under vacuum right?

You might have to jump it a few times to get the juices flowing then it should start short cycling and you can add refrigerant from there. I've had some play hard ball like that back when charging by cans.

 

[koda2000]

I believe an empty Explorer A/C system should take about 3 lbs of R134 refrigerant. Sometimes you need to make/force the compressor run to get it all in.

You can run 12V power straight to the magnetic clutch's connector, using a jumper wire, to force it to run while adding refrigerant.

 

[Collin Whitfield]

I just charged my A/C yesterday and the charge is 1lb 14oz.

 

[koda2000]

I just charged my A/C yesterday and the charge is 1lb 14oz.

Internet search "Ford Mechanic" says 56 oz's for dual air on a full recharge w/vacuum pulled. That would be 3.5 lbs, but you can't always trust the internet. How did come up with 1lb 14oz?

 

[boominXplorer]

It's on the sticker under the hood. 1lb 14oz sounds right though.

 

[IsaacJB97]

I force charged it and got it to approximately 30oz or 1lb 14oz and nothing. The gauges once charged read 32 low side 80 high side. Since I already put on a new low cycle switch, while I was out getting a new clutch connector pigtail I got a new WOT relay and high pressure switch. Wired up the new clutch connector pigtail and put on the new high pressure switch and relay. Still nothing.

Since it’s fully charged and both switches work I jumped the compressor from the WOT relay and the system kicked in and was blowing cold. As soon as I pulled the jumper wire and put in the brand freakin new relay, I got nothin. I’m completely baffled at this point.

 

[koda2000]

Maybe a dumb question, but have you checked your fuses? I'd check every damn fuse that the vehicle has.

Also, do you have the manual or automated climate controls? The automated (EATC) circuit board has been known to have solder joint problems, which prevent the A/C from kicking in.

 

[IsaacJB97]

Maybe a dumb question, but have you checked your fuses? I'd check every damn fuse that the vehicle has.

Also, do you have the manual or automated climate controls? The automated (EATC) circuit board has been known to have solder joint problems, which prevent the A/C from kicking in.

I changed all the fuses related to the system I could find. None of them were bad but I replaced anyway. It is automatic and I was hoping to God I wouldn’t have to take it that far. What does a replacement cost and how difficult on a scale of 1-10 is it to remove/replace? The weird thing is, when it stopped working last year it wasn’t sudden. The air got warmer and warmer for about a week and then that was it. I assumed it was mechanical and not electrical but down the rabbit hole I went!!!

 

[koda2000]

Again, I would check ALL the fuses to begin with. I've been bitten by stuff like that in the past.

The EATC control module is easy enough to change out (a 2 on a scale of 1-10) and the rebuild cost is around $100 + shipping. If you're handy with working with electronics and a soldering iron, some here have fixed there own circuit boards. There's also a way to run diagnostics on the control module (push certain buttons and hold them down for so many seconds) but the diagnostics have never helped me in the past. You seem to be a bit quick to throw money at a problem without knowing what the problem is, so I'm not suggesting you run out and have your module rebuilt. I'm just saying it's a possibility. I have the benefit of swapping parts around between multiple vehicles to see what works.

Read this thread...
AC inop

 

[shucker1]

I jumped the compressor from the WOT relay and the system kicked in and was blowing cold. As soon as I pulled the jumper wire and put in the brand freakin new relay, I got nothin.

So when you jumped the WOT relay all was good.

You put the relay back in service and everything quit?

Therefore you have no "Command" for the WOT relay to go closed.

You may want to check fuses like @koda2000 said or inspect the source of command for the WOT relay.