A/C compressor not kicking on after evacuating system

System has been completely evacuated. Had a vaccuum running on it for a few hours and the pressure held steady after taking the vacuum off. Go to recharge it and the compressor won't kick on and I can't get any r134 into the system.

It was working fine yesterday...no clue where to even start. The A/C light on the button lights up and i can push the clutch without a problem so it's not seized.

Hoping it might just be the clutch, but seems odd that it was working yesterday and not today.

 

I believe there is a low pressure switch that will keep compressor from running when the refrigerant is low. I think you have to manipulate the compressor into running. At least that's what I've had to do on other vehicles. Not sure on the taco but gotta be similar

 

If that was the normal process for when you evacuate the system, wouldn't that be in the factory service manual? I don't see it.

I don't see anything in the FSM about needing to coerce the compressor into starting when the pressure is low. I haven't seen anything about that in any tutorial either. The process is always just evac the system, and add r134. Enough pressure builds until it starts to suck it in.

 

Yes, once enough pressure builds the compressor should kick on. It might take a few minutes for the r134 to work its way to the pressure switch, but if you have a set of manifold gauges on it you'll be able to see what the pressure is on both the low and high sides. It should be something like 30psi for the compressor to work, but you can check the repair manual for the exact spec.

 

I have gauges and have the entire system evacuated and holding pressure. The compressor won't kick on like it's supposed to.

 

Did you check the AC fuse? The light on the button may be on a separate circuit, so it's not indicative that the AC system is receiving power.

 

Your putting freon into the low side right? Is the gauge rising on the low side? Is the truck running? Is the ac light on when you press the button?

 

If your system is evacuated, you should be holding a vacuum, not (positive) pressure. You will not see pressure until you charge the system with freon. The compressor will not engage until you have enough freon in the system to reach the prescribed pressure (whatever the pressure switch needs to see).

 

Yup. Low only. When I go to recharge after pulling the vacuum, I open the valve on the can, then purge the line. Start up the truck with AC on, circulate on, and set to coldest. Then slowly open the low side. The pressure on the low side goes right up to ~67. Compressor won't kick on though so very little to no r134 is getting pulled in.

Yup, fuse under the hood is good. And from the research I've done there isn't a main relay to access to be able to jump/replace.

I want to try and jump the compressor while it's attached but there isn't much room in there. The power steering pump is right above it and in the way. I'm struggling to see where I can connect the leads

Right. But once i turn the truck on to charge it and open the low side to let the r134 in, the pressure goes to ~67. Compressor isn't kicking on though.

 

It would be good if you had a wiring diagram of the AC system and blower motor. On other Toyotas there is a heater fuse that powers the blower motor and heater relay. The heater relay powers the AC fuse and there is a relay between the AC fuse and magnet clutch (labeled something like AC MG relay maybe). With a wiring diagram you could test for voltage at different points, for example, with blower fan on and AC switch on, test for 12 volts at AC fuse (1 probe on battery negative, 1 probe on AC fuse socket terminal).

 

How did you pull a vacuum?

 

they changed the r134 cans to a kind of self sealing top, just because you pierced the top of the can doesnt mean that freon is leaving the can. You might have to open and close the piercing valve until freon flows.

 

I was wondering if there was a chance that my can was faulty. I've pierced it and tried to use the can to recharge 4 or 5 times now. Problem is, the can is still full so I wasn't sure how I could remove the valve without letting all the r134 escape.

With a vacuum pump.

 

Machine should give you an option to fill up via the high side or low side. Make sure engine is running and AC is set to Max recirc and High settings.

 

What about the gauges how did you have that setup and operated?

 

Can you temporarily jump out the low pressure switch to get the compressor to run drawing in the freon?

 

When I rebuilt my AC system on my truck, I didn't have to jump the compressor to make it draw in. I followed this tutorial:
https://www.tacomaworld.com/threads/1st-gen-a-c-system-replacement-how-to-seized-compressor.293204/

Maybe you have a blockage in your line, or maybe the manifold?

 

You can turn the freon can upsidedown for a second to get liquid in, then wait a little and turn it again for a second. You don't want too much liquid in the system on the low side or it can damage the compressor. When the freon leaves the can you can feel the can get cold.

Don't fill through the high side or the compressor will overpressurize the freon can and cause it to explode. It might have that warning on the can.

 

sometimes you have to screw and unscrew the piercing valve on the can to get it to flow.