Reasons for no power to A/C compressor?

[gigem891]

Hello fellow 4Runners,

My 2001 4Runner Limited, 2WD, 3.4L, is not blowing cold air, and the A/C clutch is not engaging. I'm trying to determine if either compressor or clutch is dead. Pressure test of freon shows full charge. A/C button light on in dash, and engine RPM rises and stays up with A/C on and engine running.

General question: What are situations which would not allow 12v to get to the A/C compressor?

Tests: Jumped pressure sensor switch, no change.
Checked, with no voltage with engine/AC on at compressor clip
Checked, with no voltage with engine/AC on at clutch magnet clip.

So, other than testing AC and clutch relays, if both of those are good, what conditions would prevent the 12v charge from reaching the compressor besides a short in the wiring?

In other words, if either the compressor or the compressor clutch have failed, would this activate a sensor signal to prevent 12v from being sent to the compressor? Does a truly 'fried' magnetic clutch not even pull 12v, because it cannot run its course to ground?

I have not yet tested the magnetic clutch relay, which I cannot locate.

Note: The engine RPM's increase normally as if the A/C system should be energized. That is what is confusing me.

Thank you very much,

Chuck

 

[nely]

You will see 12v if it is getting to the compressor clutch even if it is fried.

Clutch relay or wiring would cause no voltage getting to the clutch.


Sent from my iPhone using Tapatalk

 

[TheDurk]

^^^what he said.

Clutch relay is behind glove box, left side about knee high. It has a dark gray 2-row 10-pin pin plug.

http://tacoma.site40.net/4Runner_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/ewdtmc2/ewdtmpdf/ewdsourc/2002/024runne/systemci/056aac.pdf

 

[gigem891]

Thank you both very much

 

[ZionXIX]

I actually had to remove the lower bar that the bottom of the glove box is attached to. The relay and wires are basically touching the backside of that bar. I could not get the little clips pried apart to unplug the relay. Perhaps you will have better luck.

 

[gigem891]

I located the relay connector, just behind the flat 'bar' as suggested. With car running, A/C on, and connector attached to relay, I am getting 12v from 2 of the wires from the pigtail clip, leading me to believe that the relay is receiving power, and activating to send power along to the compressor clutch. Can't figure out how to remove the relay itself from the underdash assembly, but it seems like the relay is operational either way.

Will test under hood once more in search of any power along wires there, one more time.....

 

[gigem891]

Please let me know the best way to access/detach the pigtail clip on the compressor for my 2001, 2wd, 3.4L Limited Runner, with all assemblies( belts, etc.), installed. I am having a VERY difficult time unhooking this clip which is attached to the top of the compressor, to test it properly. AC lines, belts and such, are so in-the-way, and I can't get in there with my hands to unhook the compressor pigtail to properly test it for power.

Any advice would be greatly appreciated.

Thank you,

Charles

 

[gigem891]

Again, please 'spell it out', as if you are talking to a newbie. I have tried many times, but the close quarters, and cramped hands-issue is very difficult. I must be missing something.

Thank you!

 

[gigem891]

Ok, it came to me waking up this morning that maybe I'd have better access if I removed the air intake box. Duh. And voila! Clip removed, tested positive for 12v going to it. Further examination revealed positive wire from clip to clutch was severed about an inch from where it attaches to clutch. That explains that, and it most likely occurred when the pulley belt fragged a month or so ago.

So now I need to jump the clutch side of the severed wire to see if clutch even works. I can almost guarantee that compressor is ok, so replacing entire compressor/clutch assy. with all that's required to vacuum and recharge would be overkill. If jumping clutch works, and I can splice the severed power wire, that may be all that's needed. Not optimal, but good for now. But if clutch DOESN'T work when jumped, maybe only new clutch needed? Wouldn't it come with new positive and ground wires anyway? We'll see.....

 

[gigem891]

Jumped the clutch wire and clutch engages just fine. Remaining bit of severed clutch wire too short to splice any kind of way @ 1" long due to close quarters in there. Tried and failed, so will now plan on replacing clutch assembly on mounted compressor. Need write-up, but would imagine removing radiator fan, fan housing, and all the belts will suffice for room to work in.

Any advice or direction to write-ups greatly appreciated.

Thanks in advance.