RockRogue

Hey guys,

my 2003 Tacoma started to really like the A/C recently. My A/C clutch engages as soon as I turn the fan on, no matter what temp the controls are set to, and also no matter if I have the A/C button on or not. Even when the amber "a/c" light is off, the clutch stays on.

I tested all combinations of the temp (hot or cold), A/C button (on or off), and air recirculation. I also tested it at low and hi fan speeds. All conditions resulted in the A/C clutch wire getting 12v+ (checked with a DVOM). See images below of said wire.





After that, I wanted to see what the A/C button looked like, so I tore apart the climate control module. The A/C button operated a surface mount momentary switch. Just for fun I tested both the A/C button and the recirculate cabin air button. Both had .0 ohms when depressed, and infinite while at rest. Here are a few pics of the unit during testing:





I can't think of a part in this system that could be failing. IT is my understanding that the system operates like this:

Imput to climate control: 12v+ and ground
Conditions for A/C clutch engagement and A/C light illumination: Fan speed above 0, A/C button pressed.
Output: 12v+ to A/C clutch

Am I missing something? How could the circuit board's logic operate the light correctly and not the A/C clutch? Anyone have the wiring diagram?

JamesD

The A/C compressor turns on if in the defrost mode even if the button is not pressed and not lit so you may be chasing your tail on this one.

James

ZGjethro

I logged back in here to address the same issue in my 1999 SR5 4runner. I am going to check out the dash settings next time I am on the road.

RockRogue

What do you mean defrost mode? Like with the system trying to defrost itself or the window defroster on? It was 85 degrees outside when I did the diagnostics.

Nuthuts96

iTrader: (1)

^he meant the ducting selector (windshield/dash and floorboards/just floorboards, etc...) the windshield option turns your a/c on automatically, so just make sure the selector is on anything else while troubleshooting (though, it sounds like you are far beyond this elementary step...)

good luck! (God knows i need it when i get knee deep in electrical)

JamesD

You saved me some typing!!:

James

ZGjethro

Thanks for posting this. I was chasing the same problem, but I had not torn into it yet. It also seems to be linked to the temp selector. If I was if defrost and moved the temp selector out of the blue range, the AC went off.

jason191918

The "defrost" mode in terms of keeping the evaporator from icing up is done by shutting off the compressor, not turning it on.