Electrical/Vacuum Trouble Diagnosis; Operational Test - GMC G Service Manual

IB-18 AIR CONDITIONING

ELECTRICAL/VACUUM TROUBLE DIAGNOSIS

When diagnosing problems in the electrical and vacuum
systems, refer to "System Operation" and "Functional Test."
For electrical wiring and vacuum diagrams, refer to figures
19, 20, 21, 22 and 23.
Ports on rotary vacuum valves are illustrated to provide
simplicity in following vacuum schematic lines, but are num­
bered in consecutive order on the actual valve.

OPERATIONAL TEST

To determine if the electrical, vacuum and refrigeration
systems are operating efficiently, do the following:
1. Operate the blower at four speeds and check the
compressor clutch engagement. This indicates that
the electrical circuits are working.
2. Check the hand felt temperature of the evaporator
inlet pipe and accumulator surface. The same tem­
perature indicates a properly charged system.
3. Operate the A/C control selector (mode) lever to dis­
tribute air from the outlets. This will check the vacuum
and diaphragm function.