Author Topic: AC cold at idle - hot while driving  (Read 148 times)

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Offline zagracing

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AC cold at idle - hot while driving
« on: July 03, 2020, 10:43:30 AM »
Hey Lads,
So interesting problem and I will review all to get to the fix as quickly as possible.
Bullet Points:
- 1998 Damon Ultrasport - CAT275 on Freightliner Chassis
- Entire AC system was replaced by me except the evaporator
- Dual fans on condenser
- New bypass valve on heater (cable actuated)
- Everything operates nominally

So I am seeing a charge at idle in 80 degree ambient temps of 30 on the low side and about 125-130 on the high side.
At idle, the system is getting down to the 50 degree range. Not super cold but that's 30 degrees below the ambient which is healthy.

As soon as you start driving the rig, the air goes warm and I have never encountered this before. I put the gauges on the system at idle and rev'd the engine but the pressures remain static - they do not rise or fall but under load, something changes.

Since the AC / Heater bypass is cable actuated, I don't suspect it to be related to vacuum
It could possibly be a system that has been overcharged triggering the high pressure switch when moving and building too much pressure but I don't have a means to run gauges while driving.
Honestly can't think of anything else so I come to you guys.

I know that typically, for most AC issues the reverse is true so maybe I am on the other side of that? Too much Freon triggering the high pressure switch when moving.
Any help is greatly appreciated while I continue my research on the net

Also - can anyone tell me how much R134a goes into the Freightliner XC chassis by volume and or weight?

« Last Edit: July 03, 2020, 11:33:11 AM by zagracing »