AC Troubleshooting

[Filthy Filbert]

My AC is not working.

Discovered I have the new garbage R1234 system. So I ordered the adapters to use with my AC gauge set. Thinking "probably a bit low. Let's check pressures and top off as needed" well, I found that I'm at 90 PSI in the system, which seems like enough that I should at least satisfy the pressure switch and get the compressor to cycle to give me high and low pressures.

So, on to the next step in troubleshooting. But I'm not sure where the pressure switch is. Did they move it into the compressor? I see 2 pigtails coming out of the compressor but I don't know what each one is for. Is there a FSM that I can download anywhere with the wire schematics and all the different sensor locations?

I'm going to be annoyed if I have to replace a $300 compressor because of a $10 switch that used to be inline before the oriface nozzle on the older R134 systems...

 

[Filthy Filbert]

Nobody has done any troubleshooting of their AC? I even tried to access the sensors and stuff with my AlphaOBD but I don't know what I'm doing. I go into body computer, HVAC, it shows connected but I can't see how to view status or condition of sensors, power to the AC clutch, etc.

 

[QwikKota]

Should be a pressure transducer on the high side line. Perhaps 68308727AA?

 

[Filthy Filbert]

Should be a pressure transducer on the high side line. Perhaps 68308727AA?

Is that on the high side at the compressor? I was curious why the compressor had 2 pigtails on it. I'm not used to that.

Also, I have AlphaOBD. Why can't I see the system pressure and whether it has a good signal or not, or how to tell if the PCM is commanding the AC clutch to come on or not? The software is just not very user friendly.

 

[QwikKota]

Is that on the high side at the compressor? I was curious why the compressor had 2 pigtails on it. I'm not used to that.

Also, I have AlphaOBD. Why can't I see the system pressure and whether it has a good signal or not, or how to tell if the PCM is commanding the AC clutch to come on or not? The software is just not very user friendly.

Away from the compressor there is a transducer/pressure switch on the high side line. The upper connector should be for the clutch and the lower rear connector should be for a pressure transducer or solenoid.

Not familiar with that software/tool but you should be able to hear the clutch click if there is enough pressure in the system.

 

[Filthy Filbert]

Away from the compressor there is a transducer/pressure switch on the high side line. The upper connector should be for the clutch and the lower rear connector should be for a pressure transducer or solenoid.

Not familiar with that software/tool but you should be able to hear the clutch click if there is enough pressure in the system.

So there's 2 pressure transducers? I'm trying to figure out what the plug circled in blue is for and whether it should be a switch or a transducer that sends an analog signal. I don't hear the clutch clicking at all over the sound of the engine idling. It's definitely not spinning though, and pressures never fluctuate between high side and low side. Is there a set range the pressure transducers need to be in between or would it be possible to trick the computer into turning on the AC Clutch with short(12v+) and open(0v)

 

[markabby]

So there's 2 pressure transducers? I'm trying to figure out what the plug circled in blue is for and whether it should be a switch or a transducer that sends an analog signal. I don't hear the clutch clicking at all over the sound of the engine idling. It's definitely not spinning though, and pressures never fluctuate between high side and low side. Is there a set range the pressure transducers need to be in between or would it be possible to trick the computer into turning on the AC Clutch with short(12v+) and open(0v)

my 2020 shows a large fat harness connected there

 

[QwikKota]

That bottom lower one is what I'm talking about as well. It may be a solenoid that closes if it sense pressure loss. My home a/c has that to save the freon from leaking out. I would think you would need to close the circuit on the clutch as well as open that solenoid but the latter may be riskier.

 

[crash68]

It may be a solenoid that closes if it sense pressure loss. My home a/c has that to save the freon from leaking out.

Solenoid valves are not installed to stop refrigerant from leaking out, typically they're used to stop the migration of refrigerant when the compressor isn't running usually in systems with long line sets.
I have attached some wiring diagrams of a '15 truck, one is for manual temp control the other is the automatic temp control (dual zone trucks).

 

[Filthy Filbert]

I found a pressure transducer up by the passenger inner fender. I can't probe it without damaging insulation though, so I'm hesitant to try or I'll have further problems in a couple years from corrosion.

I did jump power to the AC clutch and immediately got nice cold air inside the cab, so I think there's a signal problem somewhere. Wish my AlphaOBD would show me status of sensors and clutch engagement. it says "connected" when I connect to HVAC through the body computer, but I can't figure out how to monitor pressure transducers or AC Clutch commanded condition.

I see no blown fuses on the panel by the battery on the driver side fender.

I may attempt a hail mary and try the transducer on the passenger fender, but I don't remember, can those be removed without evacuating the freon, or will removing the transducer vent off all the freon?

Does anyone know if the 2020 Classic wiring would match up with a 2015? After my weathertech floor mat fiasco, I have zero faith that this truck is like any other modle year...

 

[chaosh1]

I found a pressure transducer up by the passenger inner fender. I can't probe it without damaging insulation though, so I'm hesitant to try or I'll have further problems in a couple years from corrosion.

I did jump power to the AC clutch and immediately got nice cold air inside the cab, so I think there's a signal problem somewhere. Wish my AlphaOBD would show me status of sensors and clutch engagement. it says "connected" when I connect to HVAC through the body computer, but I can't figure out how to monitor pressure transducers or AC Clutch commanded condition.

I see no blown fuses on the panel by the battery on the driver side fender.

I may attempt a hail mary and try the transducer on the passenger fender, but I don't remember, can those be removed without evacuating the freon, or will removing the transducer vent off all the freon?

Does anyone know if the 2020 Classic wiring would match up with a 2015? After my weathertech floor mat fiasco, I have zero faith that this truck is like any other modle year...

No it cant be removed with pressure on the system.

I suggest piercing the insulation and check for power in and out of the transducer. Obviously if you have in and no out its the transducer or a pressure problem otherwise its more upstream as in the a/c control panel

 

[QwikKota]

Solenoid valves are not installed to stop refrigerant from leaking out, typically they're used to stop the migration of refrigerant when the compressor isn't running usually in systems with long line sets.
I have attached some wiring diagrams of a '15 truck, one is for manual temp control the other is the automatic temp control (dual zone trucks).

Leaking out and migration aren't the same thing? Hah

 

[crash68]

Leaking out and migration aren't the same thing?

To someone who knows refrigeration, leaking out means the system is losing the refrigerant.
Stopping the refrigerant from migration means your keeping the liquid refrigerant on the high side of the system as to not flood the low side with refrigerant which can damage the compressor during start up.

 

[Filthy Filbert]

No it cant be removed with pressure on the system.

I suggest piercing the insulation and check for power in and out of the transducer. Obviously if you have in and no out its the transducer or a pressure problem otherwise its more upstream as in the a/c control panel

Shoot. I read somewhere that there was a shrader valve under the transducer and that it could be removed with freon in the system.

I know my pressure is good. I haven't taken high/low readings while it's running, but at steady state/engine off I'm reading 90 psi on both gauges, and when I put power directly to the AC clutch the low pressure side started forming condensation and the vents were blowing cold.

...It's tempting to toss in a switch to manually turn off and on the AC clutch as needed but I really don't want to do that. but if changing the transducer will vent off the system, a $1 switch sounds better than $200 in freon. I'm gonna miss R134. I could pick that stuff up at Rural king for $5 a can!

 

[markabby]

there's cans of r1234 available.

Pardon Our Interruption...

 

[Filthy Filbert]

there's cans of r1234 available.

Pardon Our Interruption...

Oh. That's a lot cheaper than I was seeing the last time I looked around

 

[QwikKota]

I removed the valve core on my Dakota once while under about 30 psi. Holy hell, that was an experience. I doubt you can remove it without losing almost all of your refrigerant. I got the replacement back in before I lost all pressure but it was not a safe thing to do.

 

[Filthy Filbert]

there's cans of r1234 available.

Pardon Our Interruption...

By the way, buyer beware! What was a good price was actually NOT a good price. I did not read the fine print and just saw the photos in the ad. When the box arrived and I opened it, I said to myself "Hell, these cans are empty!"

I'm used to R134 that comes in 12 oz cans. These are roughtly the same size but they are only filled to 4 oz!!! it takes 3 cans to equal one can of R134. R134 is around $0.60 per oz give or take. This R1234 ended up being $5.00 per oz!!!!!

Thankfully I didn't need any refridgerant and discovered a missing fuse thanks to the electrical scematic that was posted above. The lid to the fuse panel leaves a lot to be desired and I was looking in the wrong location.