Make: Western Star
Engine Size: 500 Cat
Refrigerant Type: 134A
Pressure Low: empty
Pressure High: empty
Country of Origin: Canada
Have to do a ac system on a highway truck. I found a leak on it last year, fixed the leak and it worked good till owner had a line rub threw so he lost the charge. When I charged it the last time I wasn't able to get the full 5.5lbs in it. Truck has a big bunk on it with ac in the bunk similar to rear ac in a van. It seemed like there was no freon getting to the lines into the bunk. Under the bottom of the expansion valve on the fire wall 2 lines come out from underneath the expansion valve to go to bunk and these lines were warm. Could it be possible these lines have been blocked off at the valve????? I put about 3.5lbs in and the the front system worked flawlessly, 42F on the hottest day but nothing in the rear. It seems to make sense that if the rear is isolated it will hold less. I have seen bunks blocked off before if something malfunctions and the owner doesn't want to pay to fix it they block it off.
Look for an electric valve in the lines to the rear. It would be wired to open only when the rear fan is on. This system probably has dual TXV's, so the rear TXV could be blocked. I suspect the lines leaving the front TXV are just teed into the system before the valve, and the front TXV only controls the front evaporator.
If there's an electric valve, you also need it to stay open during evacuation in order to properly evacuate the system. Hotwire it if necessary.
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