Bought my truck, a 2004 Tacoma about a year ago and I hadn't noticed until this summer that the air conditioning always blows as long as the fan is set to on. I observed that the compressor does disconnect with the engine running and the switch in the off position. If I set the fan to position 1-4, whether the A/C button light is on or off, the compressor is engaged. I'm getting cold air in the winter and it's affecting my gas mileage. I'm considering removing the belt as a short term solution, but I was hoping maybe someone could give me some insight to a better fix. If it was stuck on all the time, I'd assume the clutch is jammed, but this obviously is a wiring problem.
Thanks!

 

Have you checked compressor engagement on different vent settings? Newer Toyota's use defroster linked ac if either defrost or foot/defrost vent settings are selected the compressor will engage to dehumidify the windshield. If it's running on all vent settings with ac button off, possibly a bad ac amplifier.

 

You were right. I switched the vent and it turned off. I almost always run the vent on the window and my feet. I feel stupid, but I think it's dumber that Toyota would wire it this way without making the A/C light come on.

 

I don't like the feature either my 02 corolla had it and I didn't like it.

 

my 98 tacoma did the same when i had defroster on. Took me a few days to figure it out.

 

I have a 2004 Nissan that also has a similar feature. As I move the vent switch to defrost, the air conditioning automatically turns on and recirculated air turns off. However, the A/C light illuminates and if I press the A/C button, I have the option to turn it off. This is how the system should work. Thumbs down Toyota.