Over the weekend I noticed that my air conditioning compressor was not working. The clutch does not lock up to be exact.

I figured blown fuse - the fuse was good - checked the A/C circuit breaker
it was good. Both of these are located behind the glove box.

Checked the compressor wire again to make sure that it was connected.
I unplugged the wire and checked for voltage with the engine running anf the A/c switch at the dash on - no power.

I removed the grille and got to the low pressure switch at the sight glass.
installed a jumper wire - compressor still does not kick in.

I hooked a power wire from the battery to the compressor lead and it immediately locked up and the suction line got cold. OK - I figure that the dash switch has gone bad even though the light is coming on. I borrowed the switch from my sons Tacoma - still nothing.

Any other idea's ?

This is a 2nd generation V-6 4 runner 4WD for the record.

 

Bump Bump Bump

Anybody had this problem ?

 

Try this forum http://www.autoacforum.com/

 

Personally, I'm guess low level of refrigerant. What happens is, if you have a low level of (in your case R-12) refrigerant if you still have the original system), as a safety mechanism, your compressor will not engage until you recharge your system. Obviously, you have a leak somewhere in your A/C system if that's the case and since R-12 is like liquid gold these days (I get it at cost for $3.00 an oz, NOT lbs, and remember 16oz to 1 lbs) therefore, make sure you figure out where the leak is coming from before you recharge and remove & replace that particular part.

Oh yah, I had the same problem on my old '90 4Runner and my A/C was in fact leaking at the schrader valves (oddly enough) but that wasn't the only place. I never figure out the rest as the vehicle was sold afterwards, but you can tell by a dirt buildup at the site of the leak as oil tends to leak out at that area and coat whatever it is, if it's a big enough leak.

 

I do not believe that I have a leak - I can jump the low pressure switch and the clutch still does not engage. I ran 12 volts directly to the compressor and the clutch engaged and the air immediately got cold. My problem is no power to the wire to engage the clutch. I ruled out the 10 amp fuse, the 40 amp circuit breaker and the actual A/C switch in the dash. The wire is not damaged and the truck is maintained religiously by me. Hell the engine compartment is as clean as the outside of the runner.

Any other idea's ?

 

Oops I didn't read your first post in its entireity...you did jump the low press switch...my bad. And you said you had power running through the clutch wire, fuses checked, switch checked, and you said you checked the wire, in it's entirety?...when you engage the A/C , you followed the path and it has no power being sent to the clutch...geez, you got me stumped on this one... It's been a while since I worked on an a/c electrical, but the two ideas I would start to think of is inside the evaporator a safety temperature bulb (I forget what it's called) but I wondering if there is an issue with that (that small bulb prevents ice blocking of the evaporator, by disengaging the compressor clutch), or perhaps your line pressure is too high (a result of overcharging) (high-pressure cut-off switch).

Did you in fact check your high and low side pressures? If you did what are they?

Another far-fetched idea, some cars have a safety mechanism built-in that will not engage the clutch if the accessory belt feels too much resistance (ie., seized clutch) to prevent accessory belt breakage...but again that's far fetched.

 

i second that its probably the temperature sensing bulb/amplifier on the evaporator...

 

Lets see - Evaporator inside ? Condenser outside - forward of radiator ?
right ????

I have not checked the pressure with a set of gauges - It has always been
cold enough to blow snow - the problem is that the A/C switch does not send
power to engage the clutch. I may have to have it check out at the A/C shop here in town. I was hoping to fix it myself but I've checked everything that I know to check - sensing bulb sounds like something that
goes in either the pressure line or the suction line. Is it just plug and play ?

Thanks for the help !!!!

 

Actually now that I think about it....I'm such an idiot :pat:

You said you bypassed the low pressure cutoff switch, then the compressor activiated, okay...well, then, there you go ...you're low on refrigerant in this case. You can rent the gauges at any Autozone for free. Just do that first as I still think your low on refrigerant.

Fyi...that thermal bulb is near the evaporator coils (inside the case which is located generally behind the glove compartment).

When you start messin with the evaporator, unless you have an appropriate a/c evacuation machine, best leave it to a shop .

 

Nope - I checked the low pressure switch by jumping the connector - the clutch did not engage. The only way that the clutch will engage is if I unplug the connection on the wire going to the compressor - when I apply direct voltage to the connector wire going to the compressor - then the clutch locks and the suction line gets cold - refrigerated air comes out of the air vents.

I am positive even without the gauge test that the refrigerant is good enough to work. Something between the A/c switch in the dash and the connection at the compressor wire is not working. Fuse is good - even replaced with a new one. Circuit Breaker is good - both of these are behind the glove box - that side of the dash is still apart. I've checked all connections that I can see. I hate to be raped by a shop but I guess that they could fix it.

Doc

 

Doc, I dont know a lot about this, but just thought I would give you my thoughts.

Have you tried to idle up the engine to see if the clutch engages? It could be the idle up switch on the intake. May need adjustment.

Like I said, I dont know much, just a thought.

 

Will
I does not work when I drive the runner - I've been testing and playing with it for a week now off and on. I looked at a diagram yesterday for a Tacoma truck and it shows an A/c Amplifier ( computer ) - I suspect that it is a processor problem. I know enough to be dangerous but the basic's I will tackle ! I'll get it to the shop when I decide to give up - I'm pretty stubborn !

 

ok, sorry, I hate to see you take it to the dealer or some other shop. Maybe some else will have the majic answer. Good luck with it.

 

Thanks Will - see ya at Tellico - Is it May yet ?
Is Mikey going ?

I still got mod's to do before I go - bought a set of stubbs sliders and
I hope to be locked with an ez locker by then. Aussie does not make one for the V-6 rear end yet.

 

Yeah, mikey is going but he isnt going to wheel his rig this time. he doesnt want to break something and then have an emergency with the wife being so close to her due date. He will be riding along with me as my spotter
PM him ,he know a bit about AC. He doesnt check the board much, so I'm sure he doesnt know about this thread.
See you at Tellico

 

Doc279,
I am having the exact problem with my 91 sr5, I was wondering what if anything you ever found to be wrong.
thx in advance.

 

Wow this is an old thread. Anyone ever figure it out? I have the exact problem

 

Ya I'm having a simular issue I cant find my low pressure cut off switch though. 89 4runner 3.0 with 3.4 swap.

 

Here's reviving an old thread. I have the exact problem as described above. I've got a 95. I've troubleshot it down to the A/C Amplifier.

Anyone know where to get one outside of the dealer and boneyard? I checked Rockauto; but, they don't even list it.

 

Also, where is the A/C Breaker and/or fuse. The OP stated it was located behind the glove box. I did not find it there.