92 4runner a/c doesn't work. Compressor does not engage and the blue dash indicator light does not come on when I press the switch. If the light doesn't work does the entire circuit not work?

 

If you're compressor won't engage and the light remains out, I'd check the 10A fuse for the A/C system first. It's located behind the glove box on 92 to 94 Runners.

 

Doug, I not only checked that fuse (good) but also checked the other one in same area. Really baffeling

 

No problem, we'll get there.

Next check is to see if there is power getting to the switch. Use a volt meter to check this. With the fuse out, you will have power to one side of the fuse only. Fuse in, power to both sides. If you have power getting through the fuse, I's check the switch itself. By looking at the wiring diagram, it appears that the light should come on regardless of the rest of the system. A bad contact in the switch would cause the A/C compressor to not engage and the light not come on. You'll have to pull the face plate off the heater controls to get at the switch, but that's a piece of cake. Just pry gently at the edge to pull it loose. Once you get the switch loosened up you can either disconnect it and check the resistance through the switch (should be near zero resistance) or probe the wires with the swich engaged to check fro voltage going all the way through the switch. It doesn't matter which method you use. The result is the same. High resistance or no voltage, I'd replace the switch.

If you have no voltage reaching the fuse, we'll have to look backwards in the system to find the fault.

It's weird doing this on the internet.

 

Agreed.over the internet is difficult. I pulled the switch. I'll do my best to describe it....
When it's right side up looking at it from the back (looking at the pins), there is one on the upper tight and four on the bottom. Doing a continuity test with the switch depressed (as if the a/c switch is on or depressed), I don't have any reading between any combination of pins except the following:
between 1st and 2nd from left and 1st and second from right only VERY slight on the right ones. When the switch is off I only get very slight reading between the 1st and 2nd from right. All of these were with the switch out of dash.

 

Well, it sounds like the switch might be bad. If I get a chance, I'll pull mine tomorrow and check the readings. Looking at the diagram it appears only 3 of the terminals actually do anything. One passes throught the switch and activates the A/C system. The other goes through the light and then to ground. If the contact from the fuse inside the switch is bad, then the A/C won't work and the light won't come on. It shouldn't take long to pull mine and test it. Sometime tomorrow afternoon.

 

Doug, can't thank you enough for going to the trouble. Look forward to your message tomorrow.

 

OK, I pulled mine today and tested it. Between the two on the right I have .662 MegaOhms. This is high because it's the light circuit. And I have virtually zero resistance on the left two. Your readings are about the same as mine, so. . .

One thing I found out today on mine, at least and since your '92 should be the same as this. Neither the compressor will engage or will the light come on when you press the A/C switch to ON unless the fan switch is in at least low. If the fan is off, nothing works. Put the switch in low and everything works.

Hope this ends up being your problem.

 

Well, i've got a similar question... sorta. I have the old R12 system. I put my gauge on it, and it says it's in the "blue" area where it should be. when I punch the button the green light illuminates, but the compressor does not kick in. I have been unable to find an a/c fuse. The previous owner said it used to work. It's on a 90 model 4Runner. I could really use some help here. I've never trouble shot a/c's other than seeing if it had a belt on the compressor. Thanks!

 

Your fuse should also be behind the glovebox. Should be easy to get to. It's a 10A fuse, but if the light on the switch comes on, I think you'll find the fuse is good, but take a look anyway.

One thing that concerns me is the pressure reading. Though it's in the blue zone on the gauge, it's probably not an accurate reading. The reason I say this is that the A/C needs to be running to measure your low side pressure. With the A/C running, the pressure will drop significantly. There may not be enough volume for clutch to engage. It all works on volume and pressure. Too little, it won't work. Too much, it won't work. I would recommend evacuating the system and then adding the recommended amount of refrigerant. Now, since you have an R12 system and you can't get great stuff anymore, you might consider a R134A conversion. It's a real easy conversion to do. Buy a conversion kit at most auto supply stores. It will include the R134A refrigerant (one can), oil of R134A, a hose to fill with and the port adapters (R134A and R12 use different size ports). I recommend replacing the receiver/dryer also. They're fairly cheap and easy to replace. Don't forget new O-Rings for R134A on the hoses either.

I know this isn't a definitive answer to your problem, but I think that first you have to know that the right amount of refrigerant is in the system. Mine holds 1.8 lbs of R134A, so that would mean buying two cans. Also remember that with R134A, use about 15% less R134A than you would R12 and it won't get quite as cool, but it's close.

 

I got some cans of R134. What's the conversion from pounds to ounces? 16 ounces in a pound is it? The cans aren't labeled in lbs.

 

16 ounces = 1 lb. I did this conversion on my BMW because it was having the same sysmptons as you're having and it's been great. No problems and it blows nice and cold now.

 

Although many replies state that this can be a DIY operation, my days of working on these type things are behind me. Looks like it's time to see a pro.

Thanks for all the replies.

 

I'll give it a shot when I get home! Thanks!