2016 RAM 3500 - AC Has Stopped Working?

**Rustyj2022** · 03-21-2023

2016 RAM 3500 6.7 Cumming Dually.

AC quit working suddenly; I took the truck to a local repair guy, who said it was low on refrigerant and added a few ounces.

No help; he said it had an electrical problem.

Since then, i have been two the dealer and two other shops, but still no AC.

We have replaced the low-pressure switch, TIPM module, and AC/HEATER CONTROL MODEL, and still no power on the fuse F62.

Does anyone have any ideas, or have you run into this?

Can the control on the ac control panel cause this issue?

Any help is appreciated.

Thanks

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**AK Bob** · 03-21-2023

Fuse 62 gets power from the AC clutch relay.

The AC clutch relay gets control side power from the run start relay and is ground-side switched by the PCM.

I will upload the schematic for you later today when I arrive home.

I would start by checking for battery voltage at pin 85 of the AC clutch relay with the ignition on.

If power is present, install a known good AC clutch relay.

Edited post to add schematic.

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**AK Bob** · 03-22-2023

Attached is some additional A/C troubleshooting information from Mitchell.

See marked yellow sections on page 3 of 6.

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**Rustyj2022** · 03-22-2023

Any idea which relay is the AC?

I don't see anything but a 10 amp fuse for AC Clutch.

The attached photo of my TIMP was replaced with a brand-new oem one a couple of days ago.

No luck with that, either.

RAM TIPM PHOTO.jpg

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**AK Bob** · 03-22-2023

Originally Posted by Rustyj2022

Any idea which relay is the AC?

I don't see anything but a 10 amp fuse for AC Clutch.

The attached photo of my TIMP was replaced with a brand-new oem one a couple of days ago.

No luck with that, either.

RAM TIPM PHOTO.jpg

I guess that's what I get for trusting the Mitchell wiring diagram.

I physically checked my 2014 fuse box for that A/C clutch relay but couldn't find it.

I will take a look at the OEM wiring diagram and report back.

Sorry for the misleading information.

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**AK Bob** · 03-22-2023

Originally Posted by Rustyj2022

Any idea which relay is the AC?

I don't see anything but a 10 amp fuse for AC Clutch.

The attached photo of my TIMP was replaced with a brand-new oem one a couple of days ago.

No luck with that, either.

RAM TIPM PHOTO.jpg

Okay, see the OEM wiring diagram attached.

Apparently, the A/C clutch relay does exist, but it's on the Power Distribution Center (Fuse Box) printed circuit board along with the Run/Start relay.

I suspect what is possibly happening in your case is you are not getting voltage to fuse 62 because the control side of the A/C Clutch relay isn't being grounded by the PCM on C2 pin 6 (A/C Clutch control), possibly because the PCM isn't getting the correct signal from the A/C Pressure Transducer (see attached for location).

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**Rustyj2022** · 03-23-2023

Thank you.

I will take a look tonight when I get in and report it back.

It has had all of us baffled.

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**Rustyj2022** · 03-23-2023

AC low-pressure sensor has been replaced with an new OEM one.

Is there a way to check the PCM to see if it is bad or not sending a signal?

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**AK Bob** · 03-23-2023

Originally Posted by Rustyj2022

AC low-pressure sensor has been replaced with an new OEM one.

Is there a way to check the PCM to see if it is bad or not sending a signal?

The PCM needs to provide ground to the control side of the AC clutch relay.

I will check with a test light on the battery positive to see if that wire is being grounded.

If not, perform a bypass test and ground that wire.

If the compressor clutch engages, this will confirm if this is the only problem.

Next, I would confirm that the pressure sensor sends a signal to the PCM with a scope.

You could have open or shorted wiring between the PCM and fuse box on the ground wire or a similar situation between the PCM and pressure sensor.

Before replacing the PCM, you would need to check all powers and grounds at the PCM and confirm the AC pressure sensor is sending the correct signal and that this is the only signal that the PCM needs to issue the grounding command to the AC clutch relay.

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