AC not cooling

Tacoma 2008, reg cab 2.7L

Lately I’ve been having issues with my AC. Only blows hot air in all vents a little cold just on the driver side when I start the engine and drive for a bit. In the day gets very hot in my area around 100 F.

- I replaced the expansion valve thinking it was that because when the compressor kicks in the low side goes to 0 psi. High pressure side stay always at the same pressure of about 175 psi. Once the compressor kicks in it never disengage so it will stay always on.

- The LED on the AC button does not blink so I would say rpm sensor is working normally.

- if I disconnect the high pressure side sensor the compressor shuts off and the pressure on the low side increments. So maybe is something related in the compressor? What you guys think?

 

Sounds like you have a low charge, if you replaced the expansion valve then you must have recharged the refrigerant right?

 

Did you pull a vacuum on the system and add the correct amount of refrigerant after replacing the valve?

 

A/c work is not very accessible to the DIY mechanic. Step 1 in almost every diagnostic situation is to verify the correct charge amount, and this requires a service machine that most people don't have access to.

Hooking up manifold gauges and looking at pressures is not a reliable way to tell how full the system is. The gauges can show pressures up to 60-100 psi and it still may be mostly empty

Without knowing exactly how much refrigerant is in there it's basically impossible to trouble shoot the system. Well, maybe not impossible but you can expect to waste quite a bit of money throwing parts

From what you describe it does sound like a low charge level

 

Yes sadly, I pulled vacuum and checked for no leaks. I recharged the system with 20 oz of R134A as I read even used a scale to weight the cans.

Before replacing the valve I recharged the system once and overcharged it because the relief valve let some gas out.

im running out of ideas so will take it to a mechanic

 

This kinda sounds like a plugged condenser, be careful not to burn yourself as it may be hot but turn the system on and feel if there are any cool spots on the condenser. If there are then there is a restriction in the condenser.

 

I was thinking that too.
175 on High side, but 0 on the low side.

 

I would expect to see much higher than 175 if there was a blockage. Normal high side pressure is well over 200 on a warm day

Still sounds like a low charge to me

 

True if the service port was on the inlet side of the condenser but it is on the outlet side and so is the pressure switch.
The OP said the relief valve popped on the compressor (those typically pop around 500 psi) but gauge pressure was 175.

The tell will be if the condenser has a cool spot or the liquid line exiting it is cool.

 

Ah, I missed the part where he said the relief valve popped. That's almost has to be a blockage somewhere right?

 

Thats what the evidence so far suggests but let's see what the condenser temperature check reveals.

I've diagnosed several plugged condensers by checking for a cold area and/or cold liquid line.

 

Update:

Well I took the truck to a mechanic to check inside the AC lines and the condenser. Looks like the compressor is damaged due to overheating, the oil is all dirty so the receiver drier filter and condenser. I will order new compressor, condenser and filter sadly. The will need to clean the AC lines and hope the evaporator is still in good condition. For some reason I am not surprised after 200K miles of use.

 

That will do it, filter/dryer is completely plugged.
Kinda looks like someone may have put stop leak in it at some point, that stuff will kill an ac system like that.

 

Update:

So after 3 weeks I finally got the AC working again. Compressor, condenser and filters had to be replaced. I bought a Nissens compressor and the new sensor didn’t work for some reason. The old sensor had to be installed and now it’s working perfectly fine.