2017 Kenworth T880 - AC Blowing Warm Only at Idle

Question

Having an issue with my 2017 T880. The AC blows ice cold when I'm moving down the road, but as soon as I slow down or stop at a red light, the air gets humid and warm.

I checked the refrigerant charge with a manifold gauge set; pressures are 30 low / 225 high at 1500 RPM. But at idle, the high side creeps up to 350 and the low side stays around 50. The fan hub seems to be engaging, but I'm not sure if it's pulling enough air. The condenser is clean and doesn't have any bent fins or debris blocking it.

TacomaTess · Answer

✅ Confirmed fix: The problem was the electric fan override switch and the binary pressure switch. The fan wasn't kicking into high speed when the AC head pressure increased. Replacing the AC high-pressure switch on the liquid line fixed the communication to the ECM to command 'Fan High' whenever the AC is on and the truck is stationary.

FreightlinerFred · Answer

If your high side is hitting 350 at idle, you definitely have an airflow issue. Even if the fan is spinning, the clutch might be slipping. Check the solenoid that stays onto the fan hub. Also, verify that the fan shroud isn't broken or missing, as that will kill your cooling efficiency at a stop.

2017 Kenworth T880 - AC Blowing Warm Only at Idle

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