ac compressor wont engage

[TOYO 4R SR5]

Tried searching. Cant find anything related to my issue. Ive tried charging it and the system wont take any freon. The conpressor will engage if I directly apply 12 volts to it via the plug. It seems to hold a vacuum. But like I said I cant get it to cycle. I can see on the passenger side by the firewall is a pressure switch. Is there a common issue or maybe this switch is bad? Is there a way to test this sensor?
Any help appreciated.

Its a 2000 3.4 2 wheel drive sr5
And for the record I have my auto hvac license but this one has me stumped...

 

[EatonKyleH]

Tried searching. Cant find anything related to my issue. Ive tried charging it and the system wont take any freon. The conpressor will engage if I directly apply 12 volts to it via the plug. It seems to hold a vacuum. But like I said I cant get it to cycle. I can see on the passenger side by the firewall is a pressure switch. Is there a common issue or maybe this switch is bad? Is there a way to test this sensor?
Any help appreciated.

Its a 2000 3.4 2 wheel drive sr5
And for the record I have my auto hvac license but this one has me stumped...

The easy way would be to jump the pressure cutoff switch and see if it runs. I wrote a bit about this awhile ago. Check it out and if you need any other help just holler.

http://www.toyota-4runner.org/3rd-gen-t4rs/148793-please-tell-me-my-ac-compressors-not-toast.html

good luck.

 

[Atrox Caeda]

In case you need it I found this here in Tucson.

2001 Toyota 4Runner A/C Compressor

 

[TOYO 4R SR5]

The compressor is fine. The clutch engages and it cycles if I bypass the switch and everything and just run power straight to the battery. If I bypass the switch nothing happens at all though. My method of getting 12 volts to the clutch is by shoving A wire into the compressor clutch connector and running it around to the battery. But in my case a paperclip in the switch Connector did not work.
Thats why im wondering if there is another switch thats mayne not obvious or if theres another problem area I should look into

 

[19963.4lsr5]

The AC controls on the dash come to mind. Or a relay in the junction box.

Is the AC pressure switch two wire or three?

 

[IBallEngineer]

The compressor is fine. The clutch engages and it cycles if I bypass the switch and everything and just run power straight to the battery. If I bypass the switch nothing happens at all though. My method of getting 12 volts to the clutch is by shoving A wire into the compressor clutch connector and running it around to the battery. But in my case a paperclip in the switch Connector did not work.
Thats why im wondering if there is another switch thats mayne not obvious or if theres another problem area I should look into

Do you have manual or automatic controls?

Toyota is fond of using an A/C amplifier, which is VITAL to operation. What year is your truck? There is much to look at!

 

[TheDurk]

My link to the on-line EWD is not working right now. You don't say if you have manual or digital control but SR5 I'm guessing manual. I'm going by my paper '99 EWD.

Clutch engagement requires:

1. 12V+ from 10A A/C fuse, goes to...
2. A/C switch, goes to...
3. Closed circuit from pressure switch, goes to T1 blue/white on A/C amplifier.
4. Ground from Blower switch at T4 black/white on A/C amp.
5. Engine speed signal from ECM
6. Absence of low evaporator temp signal from A/C Thermister at evaporator.

Turn-on signal to clutch is 12V+ on T9 from A/C amp black/yellow wire.



To start with, I would check if you have 12V+ at blue/white wire at pressure switch. No means fuse or or A/C switch. If yes, then confirm 12V+ at T1. Then check #4 above. No ground means blower switch or it's connections. If all good, then it's 5 or 6 which are more complicated, but I bet it's 1-4.

If you have digital A/C, post back and I'll revise. Here is the link to the EWD, maybe it's working when you read this--it does go down sometimes. I hope it's not dead for good.

http://tacoma.site40.net/4Runner_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/ewdtmc2/ewdtmpdf/ewdsourc/2002/024runne/systemci/057acman.pdf

EDIT: The link came back, but it's messed up. It says manual A/C, but it's the digital A/C diagram as far as I can tell, since it shows servo motors, etc. If my description matches what you have, I can scan my diagrams if you need them.

 

[IBallEngineer]

Of course you post 1 minute after I did, I was on my way out the door for a MTB ride, but I think you got it covered [MENTION=10169]TheDurk[/MENTION]

 

[TOYO 4R SR5]

I do have 12v at the pressure switch plug. It is the manual ac controller. And the plug is a 2 wire plug. I havent have time to check the other plug yet since I work alot.

 

[19963.4lsr5]

Does 12v leave the pressure switch?

 

[TOYO 4R SR5]

Idk because I cant get the compressor to cycle so I cant add any freon so its just empty right now. If I bypass the switch with a paperclip there is power beyond the switch but still no cycling. For the sake of getting this thing figured out and to avoid having to buy a switch right now ive been bypassing it just so I know that things are fine beyond the switch as well and obviously theres a problem somewhere.

 

[IBallEngineer]

Idk because I cant get the compressor to cycle so I cant add any freon so its just empty right now. If I bypass the switch with a paperclip there is power beyond the switch but still no cycling. For the sake of getting this thing figured out and to avoid having to buy a switch right now ive been bypassing it just so I know that things are fine beyond the switch as well and obviously theres a problem somewhere.

OK, NOW I am confused, in your original post you said nothing happened when you bypassed the switch, now you say there is power at the switch, and beyond if you bypass. That would indicate the switch is bad since it IS what creates the cycling. Unless you are calling engaging the clutch "cycling".

 

[TheDurk]

Idk because I cant get the compressor to cycle so I cant add any freon so its just empty right now. If I bypass the switch with a paperclip there is power beyond the switch but still no cycling. For the sake of getting this thing figured out and to avoid having to buy a switch right now ive been bypassing it just so I know that things are fine beyond the switch as well and obviously theres a problem somewhere.

So now you are left with 4-6 on my list. #7 would be a fried A/C amplifier.

 

[TOYO 4R SR5]

Basicaly what im saying is that its between the switch and the actual clutch itself. Because even if I bypass the switch the clutch still wont engage. What I did to engage the clutch was run a wire from the positive terminal on the battery all the way around to the plug on the compressor itself and it does engage. I wont have time until friday to check out the other steps

 

[Cosmic]

AC clutch issues? check this first

I've dealt with the blinking AC light. Replaced the relay. Adjusted the Freon charge, all with what ended up being very temporary results.

Today I found the cause for my AC clutch failing to kick in. In my attempts to diagnose the problem, I pulled the plug for the AC clutch in order to jump the connection with a hot wire. Since the connector is facing down, I was having trouble with my test lead falling out. I pulled the connector away from the base where it's mounted to the AC compressor to make it easier to see what I was doing.
After pulling the connector from the mount, I was able to look inside the connector and look directly at the "blade" inside the connector. This is when I realize the blade was bent over a little. I straightened the blade and reconnected the plug. The compressor clutch now works.

Point is, if you're having trouble diagnosing a none working AC clutch, take a close look at the inside of that plug for a bent blade.

 

[OldManKamps]

My link to the on-line EWD is not working right now. You don't say if you have manual or digital control but SR5 I'm guessing manual. I'm going by my paper '99 EWD.

Clutch engagement requires:

1. 12V+ from 10A A/C fuse, goes to...
2. A/C switch, goes to...
3. Closed circuit from pressure switch, goes to T1 blue/white on A/C amplifier.
4. Ground from Blower switch at T4 black/white on A/C amp.
5. Engine speed signal from ECM
6. Absence of low evaporator temp signal from A/C Thermister at evaporator.

Turn-on signal to clutch is 12V+ on T9 from A/C amp black/yellow wire.



To start with, I would check if you have 12V+ at blue/white wire at pressure switch. No means fuse or or A/C switch. If yes, then confirm 12V+ at T1. Then check #4 above. No ground means blower switch or it's connections. If all good, then it's 5 or 6 which are more complicated, but I bet it's 1-4.

If you have digital A/C, post back and I'll revise. Here is the link to the EWD, maybe it's working when you read this--it does go down sometimes. I hope it's not dead for good.

http://tacoma.site40.net/4Runner_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/ewdtmc2/ewdtmpdf/ewdsourc/2002/024runne/systemci/057acman.pdf

EDIT: The link came back, but it's messed up. It says manual A/C, but it's the digital A/C diagram as far as I can tell, since it shows servo motors, etc. If my description matches what you have, I can scan my diagrams if you need them.

So this is an old post that I'm jumping on here.
I bought this truck a year ago and the A/C has never worked. The compressor LOOKS like its in good working condition. I have replaced the evaporator and cooling unit. The cooling unit isn't properly connected to the rest of the system yet as I'm trying to figure out an electrical issue.

Behind my dash, (right behind the black trim piece in the middle) are 2 connected wires. They're blue and white and it has a connector that connects to a black and a yellow wire. In this post you mentioned that the black and yellow wire are for the turn-on signal for the clutch. I cannot figure out where these wires go.. Could you please direct me and if you have the manual A/C wiring diagrams, please post them!! Thank you very much!

 

[TheDurk]

So this is an old post that I'm jumping on here.
I bought this truck a year ago and the A/C has never worked. The compressor LOOKS like its in good working condition. I have replaced the evaporator and cooling unit. The cooling unit isn't properly connected to the rest of the system yet as I'm trying to figure out an electrical issue.

Behind my dash, (right behind the black trim piece in the middle) are 2 connected wires. They're blue and white and it has a connector that connects to a black and a yellow wire. In this post you mentioned that the black and yellow wire are for the turn-on signal for the clutch. I cannot figure out where these wires go.. Could you please direct me and if you have the manual A/C wiring diagrams, please post them!! Thank you very much!

You really need to give me the year of your truck before I can do anything useful.

But Manual A/C for a 2002 is here:

http://tacoma.site40.net/4Runner_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/ewdtmc2/ewdtmpdf/ewdsourc/2002/024runne/systemci/057acman.pdf

 

[OldManKamps]

Oh I'm sorry! This is a 2000 SR5

 

[OldManKamps]

Basically, I need help identifying the wire and if that is why my compressor doesn't sound like it's turning on.
Another theory I have is that because there is 0 pressure in the A/C lines, the pressure switch is just not turning on the compressor because there's no pressure.

Sent from my Nexus 5X using Tapatalk

 

[TheDurk]

So this is an old post that I'm jumping on here.
I bought this truck a year ago and the A/C has never worked. The compressor LOOKS like its in good working condition. I have replaced the evaporator and cooling unit. The cooling unit isn't properly connected to the rest of the system yet as I'm trying to figure out an electrical issue.

Behind my dash, (right behind the black trim piece in the middle) are 2 connected wires. They're blue and white and it has a connector that connects to a black and a yellow wire. In this post you mentioned that the black and yellow wire are for the turn-on signal for the clutch. I cannot figure out where these wires go.. Could you please direct me and if you have the manual A/C wiring diagrams, please post them!! Thank you very much!

I got your PM. I had no idea you had answered my question. If you want me (or anybody) to come back to a thread you need to QUOTE me so I get a notification. I can't go back to everybody's thread to see if there is a new post. I do a lot of things on here.

A pic would be more useful. Your sentence is a little flaky and I can't tell if you are talking about a black-yellow wire or a black wire and a yellow wire.

The 12V trigger for the clutch leaves the AC amplifier as a black-yellow wire, transits the 8-pin IJ1 connector on Pin 2 to a Lightgreen-black wire that goes all the way to the clutch via the engine harness.

Blue-white wires are the power circuit for the A/C system. one blue-white returns from the pressure switch to the AC amplifier through the same IJ1 connector the clutch trigger goes through.

This from my paper EWD, and my scanner is on loan and I don't know when the kid will bring it back. So I can't post it. My EWD is '99, but '99 and 2000 are usually twins except for DRLs.

That said, you are wasting time if you try to troubleshoot an A/C system without a set of gauges. At Harbor Freight with a coupon you can get a decent set for $60. It will pay for itself the first time you don't go to a shop. You need to know if there is pressure in the system. Leaks are much more common than electrical issues and I really don't have time to troubleshoot an empty system.