A/C working only when truck is moving

[mario_rubio]

2018 Ram 2500 6.7L Cummins Turbo Diesel

The problem is that when the truck is not moving (for example, stopped at a traffic light or idling at home), the air conditioning does not work, and many times the compressor releases refrigerant gas, as if due to high temperature or pressure. (I know it is normal for it to release gas due to temperature or excess refrigerant.)

I have already replaced the fan clutch, checked the high and low fan relays, and they are fine. I also checked the harness from the fuse box to the fan, and it is fine. I confirmed that the relays are receiving 12V. I also checked the fuses, and they are all good.

The A/C only works properly when the truck is in motion.

I’ve noticed that the fan is always on, but it does not seem to increase speed even when I turn on the A/C. It seems like the high-speed function of the fan, which should activate under certain conditions, is not engaging. I initially thought it was the fan clutch and replaced it, but that was not the issue.

Does anyone have any advice on what to check or what to do next?

Thank you in advance

[email protected]

 

[dashbarron]

My pickup's AC works when idle, but works better when in motion. Noticed this just anecdotally when I got it, definitely blows cooler when moving. I thought it was a alternator sort of thing where it wanted more volts coming out to run the compressor harder. 100% talking out of my ass here.

 

[nlambert182]

Most work better when moving than when idling. Talking about the fan... it will always spin to some degree but what temp does the engine get up to when driving? Mine doesn't really start howling until warmer months where the outside temps get up past 70-80F, and the coolant temp gets to >195.

Another point, in 2018 the thermostat was replaced for a lower temp one, so operating temps don't get quite as hot as years prior. Years prior used a 200 degree and 2018 uses a 190.