Trying to troubleshoot AC

[birdhaus]

This is probably a common question, but searches lead me to a dead end.
I have a '99 4runner, 6cyl, high milage, almost 200k.
runs good, but I'm having AC issues. It was blowing ice cold, no drama..

I've picked up this oldie but goodie for clunking around in Louisiana.
No AC makes it a rather sweaty affair.

Here''s the background, Purchased 99 4rnr from cousin last year and AC blew ice cold, except AC switch in dash was stove in, stuck in the on position.

I replaced the switch, which seemed like a pull out, push in deal. Same part #, etc.

Well that was a brilliant move, it hasn't worked since. I tried putting in old switch, no joy.

The light on the dash shines a friendly green while mocking me with hot blowing humid gulf air..

Here's what it doesn't do: Not perceptible Compressor clutch engagement..
It all seems electronically dead. (except for the optimistic dash button green)

Theres no change in engine rpm, sound, anything when switch is engaged..

I was hoping maybe a relay switch might be the culprit.

Looking in the fuse/relay box, I dont see a relay that has anything to do with the AC clutch. I see threads on newer models that have this dedicated relay, but I can't ID one. Like the MG CLT relay...

..and of course I may be on a wild goose chase, and it has nothing to do with that.

So I'm asking, if an AC unit dies without any drama or slow degrading performance, where would you look?

Is there a relay switch for the AC compressor clutch in a '99?

Thanks for any ideas, I'll try the search engine again, but it seems to not understand my input.

 

[gamefreakgc]

Not a sure fix, but worth a shot. The trim panel is pretty easy to remove (if you have wood grain just be careful, it tends to break), there's only a few screws behind the climate controls and half of the parts just pop right out. Then you can inspect the switch itself and the wiring. I think you are on the right track in thinking it's an electrical issue.

Once you have the dash opened up you can follow the wire to the corresponding relays/fuses and see if you can find the short.

This worked for me on my previous truck when my fan stopped working on anything other than high speed. Turns out the switch had shorted and was a burnt color and a new one did the trick.

I just had my dash apart last night and I took the entire center section off in 10 minutes, it's not hard if you know what to look for.

 

[birdhaus]

Here's a pic of the 99 fuse/relay box. Newer units had a marking for the AC clutch Relay...

So where is my relay to the AC located? Obviously elsewhere..

Kick panel, behind glove box?

Thanks

 

[TheDurk]

According to my factory '99 EWD, A/C magnetic clutch relay for digital A/C systems is on the firewall behind the glove box, kind of low down towards the carpet area. It should have a white plug with ten pins but only 4 wires: white/black (ground) on pin 7, black/white (from control panel) on pin 4, black/yellow (to clutch) on pin 9, and blue/white (12V+ from GAUGE fuse) on pin 1. Relay coil is between pin 4 and pin 1 and should have ~3.7Ω resistance.

 

[Michael0789]

No AC

This is probably a common question, but searches lead me to a dead end.
I have a '99 4runner, 6cyl, high milage, almost 200k.
runs good, but I'm having AC issues. It was blowing ice cold, no drama..

I've picked up this oldie but goodie for clunking around in Louisiana.
No AC makes it a rather sweaty affair.

Here''s the background, Purchased 99 4rnr from cousin last year and AC blew ice cold, except AC switch in dash was stove in, stuck in the on position.

I replaced the switch, which seemed like a pull out, push in deal. Same part #, etc.

Well that was a brilliant move, it hasn't worked since. I tried putting in old switch, no joy.

The light on the dash shines a friendly green while mocking me with hot blowing humid gulf air..

Here's what it doesn't do: Not perceptible Compressor clutch engagement..
It all seems electronically dead. (except for the optimistic dash button green)

Theres no change in engine rpm, sound, anything when switch is engaged..

I was hoping maybe a relay switch might be the culprit.

Looking in the fuse/relay box, I dont see a relay that has anything to do with the AC clutch. I see threads on newer models that have this dedicated relay, but I can't ID one. Like the MG CLT relay...

..and of course I may be on a wild goose chase, and it has nothing to do with that.

So I'm asking, if an AC unit dies without any drama or slow degrading performance, where would you look?

Is there a relay switch for the AC compressor clutch in a '99?

Thanks for any ideas, I'll try the search engine again, but it seems to not understand my input.

1 ST! please forgive me for dredging this up.
2 my 99 t4r has this exact same predicament> AC working perfectly but the panel switch was broken. it is a manual run AC.
3 I bought a replacement switch from dealer and it installed it
4 the green light switches off and on but the clutch no working
5 this means that the low and high pressure AC switches are not the problem
6 because if they were the AC would not have worked on the way to the shop
7 NONE of the 2000 and up t4r models have the same electrical setup as this one, I have the 2000 FSM and it's wrong for my truck.
8 so my next step is to find out if the compressor clutch works. easiest way is to hot wire it.

A my first issue is I don't know where to look for a wire or a pin on the upstream end of the clutch wire where I can jump the compressor clutch to find out if it croaked. It is trapped on the compressor itself where I can't reach it without removing other stuff. I know I am going to get lots of advice about this step. But it's the way I can prove the clutch and bypass everything in the entire electrical system. Can anyone assist with this?

B does anyone have the correct Electrical diagram that shows where the clutch B+ comes from? The AC Amplifier is on the right side behind the glove box. It is a little green printed circuit board with and the part number identifies it as the correct part. If anybody could post a copy of the pages that show me what connectors that and pins that wire runs thru it will be a great help.

9 sorry about resurrecting the thread. thanks in advance for any assistance. it doesn't matter about the amplifier until I know for sure the clutch can go click click. which it did up until I installed the new replacement switch.

10 in the mean time I will disassemble the AC panel and see if I knocked anything loose when I was in there to double check that.

11 Thanks very much for your patience and assistance

all the best from a truck sometimes called "Old Paint"

TO ADD it is a manual control. I found a 10 pin plug with 10 wires that plugs into the AC Amplifier, and behind it a 4 pin plug with 4 wires. The replacement compressors have a one wire b+ with a connector somewhere near it. might have to drop the compressor to access the connector. there might be a relay between the amp and the compressor, but it must be well hidden. but so far so good, the only thing i wrecked is the clock

Michael