Problem: The vehicle was brought to the
shop because the A/C was not working.
Details: The tech connected a scan tool and
found no diagnostic trouble codes. Next he checked to be sure all
the related fuses had battery (B+) voltage. They did. After that,
the tech verified that the vehicle had a manual HVAC system with
a V5 compressor, then connected his A/C gages. The refrigerant
level was low, and the A/C compressor clutch would not engage.
He charged the A/C system with 1.1 lbs. of refrigerant.
NOTE: The low-side and high-side refrigerant
pressures at idle were: 75/140 PSI. At 2500 RPM, they were:
80/140 PSI. The A/C lines were warm, and the radiator cooling fan
was not running. He replaced the A/C pressure sensor, but it did
not help. At this point he called ALLDATA Tech-Assist.
The Tech-Assist consultant advised to first verify that the
evaporator temperature sensor, engine coolant sensor and
high-pressure sensor readings were within specifications. He
added that, if the tech found no problems, he should check the
A/C compressor control valve in the back of the compressor for
debris and make sure that the valve moved freely.
Confirmed Repair: After verifying that all
three sensor values were within specifications, the tech
inspected the A/C compressor control valve at the back of the
compressor. It was stuck. He replaced the control valve and the
air conditioner blew cold air again. Fixed!
BONUS Tech-Assist A/C Tip!
How to Test for Large A/C Leaks When the Charging
Station Refuses to Charge
Say a vehicle is brought in with no refrigerant in the A/C
system or you have completely evacuated the system. If the
recovery/charging station determines that there is a “large
leak”, it may not allow you to recharge the system. How to find
the leak under those conditions?
Easy! Use a nitrogen leak test kit to find the leak. You can
fill the system with nitrogen as per the kit’s instructions and
listen for any hissing sounds, and/or use the supplied solution
to create bubbles at the leak site.