Platypus1

Hi all, I recently did some work under the plenum of my 3.0, and now everything is back together. I dont know if this is related or what, but now my AC does not work. I took it to a shop and they said the r134a is full, we jumped the compressor and it took off, cooling the cab just fine. I checked the relays and they are working. So something..before the relays is not allowing the a/c to work. Any thoughts?

Arent there high and low pressure sensors on AC systems? If so can they prevent the ac from running?

Anyhelp would be greatly appreciated.

1994 4runner 3.0

Thanks

Steveh29

I had this happen once, It was the circuit board behind the glove box. I stupidly did some electrical work without disconnecting the battery and it fried a component of that board. Had to be replaced.

Did you check the A/C switch in the dash. Does it light up green like the A/C is running even though it isnt? If it's not lighting up, then that switch isn't working properly (or not getting power).

Platypus1

HI steve, thanks for responding. The green light does come on, along with the blower motor and everything. BUt nothing trips the relay for the compressor and condensor fan. IS this the same scenario you had? Was the board expensive?

Steveh29

I PM'd you but for the thread's sake, here's my experience:

I was removing my crummy Flex-A-Lite fan and I cut some of the wires before I disconnected the battery. Yes, my bad. There was a small spark and pop and then my A/C didn't work.

Everything appeared to be normal (AC switch, relays, fan and all) but I had no compressor activation. I pulled the board myself and a visual inspection showed no obvious signs of fryage, but that's not a very good diagnosis for a PC board. I had no data on the board so I couldn't test it. I thought the board may be fried, but I was too busy with work and needed my AC fixed. So it went to the dealer.

Dealer confirmed the board was bad and replaced it. I believe the board cost $140 but I'll check my receipts. They had to order the part which took about 4 days to get in.

In hindsight and if I'd had time, I would have replaced the board with a junk yard board or TAP supplied board. Replacing the board is easy - remove the glove box door and then you can pull it out of it's little plastic box. I just was super short on time.

Before you spend money on a new PC board, I'd be sure to use a wiring diagram to troubleshoot the system and make sure there are no other problems.

Platypus1

Did your condensor fan run during this time, or was it dead too until u got the board replaced?

Steveh29

I don't recall if it was working or not. I would think it wasn't because the condensor fan only seems to go when the compressor is running. I think they're related that way.

Yoda

The only thing I see connected to the plenum area is the temp switch in that block at the rear of the plenum (single terminal....should have a pink wire on it) I don't know how it is supposed to work, but check to make sure it is connected and not shorted. Looking at the diagram, when it is shorted to ground (pinched wire or switch activated) it shuts off the compressor. Nothing I see on my database says if it grounds when the engine overheats or if it is too cold. Unplug it and see if A/C opperates.