My air conditioner is not working?

Good morning.

The AC compressor is commanded on by the PCM. It grounds the control side of the relay when it sees the signal from the low and high pressure switches.
Have you checked the pressure switches?

Roy

https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak

20 PSI would still be a low charge. That system should hold between 32 and 38 ounces depending on the cab. You put in 24oz if the cans were full. You should be able to use a set of gauges and add in the rest and then see if the system cycles. However with the system pressure at 0 you should start by pulling a full vacuum on the system and see if you can find the leak, or with the last can use one that has dye in it. That way you could find the leak instead of just needing to keep adding R134a.

The core in the port is replaceable if it's leaking. Mo9st parts stores have those in stock. You can usually get a vacuum pump and gauge set as a loaner tool as well. That would let you pull it down and see if it has any leaks as well. If you want to opt for the dye it works as long as you can get to the area that leaks, normally that is a fitting or on that truck it could be a bad condenser core as they are known for cracking. For a UV light you can get a low cost one in stores like Walmart. They work pretty good.

Which engine and cab do you have? I can look up the correct diagram for it and see what is in the system.

Those switches are a pull to ground system so one side should be ground and the other side should have battery voltage. However that voltage comes out of the PCM after being turned on by the control module. To test the switches all you need to do is jumper them. The high switch is supposed to open at high pressure while the low side closes if there is enough pressure. If you jumper them and still have nothing then check that Fuse 12 in the IP fuse block and the 10 amp compressor fuse in the underhood block are both good.

If it's the backlighting it shouldn't be the issue, but as the entire thing is all one board it's possible that the board is corroded and that is causing the issue. I doubt it's PCM related as that is normally only connected to control the engine as the AC cycles, so when the compressor engages the PCM sees the extra load and kicks the rpms up a bit and increases the alternator output to compensate for the load on the electrical system, In your case the loads are not switching on. If jumping the switches made no difference then there is a control issue. Likely in the control module in the dash.

Okay, from here you are going to need a scan tool that can watch the PCM signals to see if the data signal from the control head to the PCM is working. Then go to the PCM up front in the engine compartment and see if it is triggering the ground control circuit at pin 43 in connector 2 (Dark green wire with white stripe). If that is going to ground in response to the dash controls but the relay isn't switching that wire has an issue between the PCM and the relay. If the control signal shows on with the scan tool but the pin at the PCM isn't grounding then the PCM is faulty.

85 should go to ground when the A/C is on. As it isn't you need to get to C2 and see if the wire does go to ground there. Using a jumper to ground at that end would tell you if it's a wiring issue or if there is something in the PCM causing an issue. This is when you need a scan tool that can see the inputs and use the bi-directional controls to turn the output on and off. If you get nothing then the PCM is the problem.

Hi,

If the system won't take freon and only works by jumping the low-pressure switch, check the Schrader valve on the low-pressure side to see if it is stuck. For it to work when jumping that switch, it has to be low on Freon.

They make replacement Schrader valves for the vehicle, but you will need to vacuum and recharge the system. You will need an A/C manifold gauge set to do it. Also, when you connect the gauges to the low-pressure side, you will know if that is the problem. It won't show any pressure. The only thing that will cause that is if there is no freon in the system or the valve is stuck.

Here is a link you may find helpful:

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

Let me know if you have other questions.

Take care,

Joe

You are very welcome. If possible, let me know what you find or if you have other questions.

Take care,
Joe