94 4Runner AC Problem
 

I have intermittent AC in a 4Runner I bought a couple of months ago. Here is what I know.

With gauges I had 70PSI on the LOW side until I got the compressor to come on. I was attempting to bleed the pressure on the low side from 70 to around 30 and noticed the high side pressure dropping as well. It was only at around 40PSI when I first connected the gauges, but when I got the compressor to come on (by putting 12V on the compressor power wire) it went up to 170 or so.

So when I can get the system to come on, it falls within normal ranges, 30 on the low side, 170-180 on the high side, but it looks as if the high side is bleeding to the low side maybe?

Also, I was also looking for the AC pressure switch and I couldn't find it at all. That is my biggest question now.

Sometimes, when driving, it comes on miraculously by itself, maybe 50% of the time. When it comes on, it is blowing at 39 degrees, perfectly fine, and the engine temp stays fine, it is just working great.

Should the high and low side pressures bleed to each other? Am I looking at a faulty compressor, or maybe a cycling switch? I am hoping for the cycling switch, I just can't find the thing.

Sorry for the heavy read, but it's alot to tell on here. Any help is appreciated.

try this.... http://personal.utulsa.edu/~nathan-b...19pressure.pdf

and heres the link to the rest of it
http://personal.utulsa.edu/~nathan-b...ditioning.html

Well, I ruined my system, at least somewhat and definately increased my labor. I checked and it appears that the pressure switch isn't switching. I could short it and the compressor and everything was fine.

SOOOO, in my attempt to remove the switch (it is very tight and still not off!!) I broke the system and shot oil and freon all over my interior. I guess I will look to see which pipe it is that is broken. I saw where the leak is, so I just have to find the next two fittings. Oh, well, nothing ventured, nothing gained.

I used to have an Eplorer that I replaced that switch on almost every year. I hope that fixes it after I get it sealed back up.

Thanks for the help, even though I am a bulldog idiot when trying to remove parts.

Any help on the actual pipe I broke? I wonder if it is a autozone or oreilly part? Thanks.

haha...goodluck with that...it is most likely a dealer part, or u could try a bone yard

Update
 

I have the hose off and I think I can weld it up at work instead of buying a new eval that may or may not come with the hose. I have the switch in my hand and it is apparently a dealer only part, so I ordered one from the dealer for 50 bucks.

I was reading the switch and it says:

HP OFF 3.14 MPa
MP OFF 1.52MPa
LP OFF 0.19MPa

Now as best I can figure, it is a hi-lo pressure switch with the high cutoff at 3.14MPa (455PSI) and the low cutoff at 0.19MPa (27.5PSI) I am not sure what the MP is for, but it is at 1.52MPa (220PSI) I did fall with the ranges before the accident, so hopefully that will fix it. That and shorting two pins on the connector made the system work and cool to 39.

The thing really wasn't that hard to get out, after completely removing the glove box and some can under the hood.

Anyone heard of these failing? I am getting to know this Toyota intimately very quickly, and not by choice.

OK. I got the pressure switch replaced, vac'ed and recharged the system. Guess what, same thing. . . I left the connector unplugged and ran a switch to the two wires that will switch the system on. I now have AC and can power the system on with the Slide switch in the dash, but it still isn't right and I really don't like running it like this.

When charging the system, I was as 200 PSI HI side and 35 LOW side @2000RPM. That appears to be in good range, and the AC is cold when bypassing the presssure switch.

What is a common failure on these systems. I have checked the two fuses behind the glove box what had "AC" on them. Both OK. I'm at a loss and would hate to blow something up on an otherwise good system except for some sensor, switch, etc.

Please offer up suggestions. . . I am still unsure about the dash AC switch. It is switching across two leads, so I think it is OK from the diagram I looked at.

Help me. Help me. . Thanks.

I have the same problem with my AC currently. Were you able to resolve the issue?

not sure about the models you 2 have but my 87 pickup has a part behind the dash called the A/C amplifier. It seems to control about everything the A/C does including the idle-up function. On mine all the switches seem to run through it too, kind of like a brain box.
I hope that might give you some insight. If not i'll watch the thread to see if you get anywhere.