GMC 1976 ZEO 6083 Maintenance Manual page 84

discussion of belt tensioning or replacement, re-
fer to "Belt Tension", SECTION 6K, ENGINE
COOLING.
COMPRESSOR FAILURE
If the compressor has failed mechanically to the
extent that metal chips and shavings are found in it,
the system should be checked for foreign material
and cleaned as described under Foreign Material in
the System .
FALSE COMPRESSOR SEIZURE
Slipping or broken air conditioning drive belts
and/or scored clutch surfaces may be experienced on
initial start up of an air conditioning compressor
after an extended period of storage or non-operation
of the compressor . This would indicate a seized com-
pressor; however, an overhaul or replacement of the
compressor may not be necessary .
During extended periods of non-operation,
changes in temperature cause the refrigerant in the
air conditioning compressor to expand and contract .
During this movement, lubricating oil carried by the
refrigerant tends to migrate from highly polished
surfaces in the compressor such as the ball seats and
axial plate. Without lubricating oil at these polished
surfaces, they "wring" together and appear to be
seized .
Before the time and expense of an overhaul is
invested, use the following check to determine if the
compressor is actually seized . With a wrench on the
compressor shaft lock nut or Spanner Wrench J-
9403 on the clutch drive plate, "rock" the shaft in the
opposite direction of normal rotation . After the com-
pressor is broken loose, "rock" the shaft back and
forth. This should be sufficient to return lubricating
oil to the "wrung" surfaces and allow the compressor
shaft to be turned by hand . Once the compressor
turns freely, rotate the compressor at least three
complete turns. Start the engine and operate the
compressor for a minimum of one minute .
This procedure will not affect a compressor that
is actually seized but should be attempted before
overhauling a compressor known to be idle for a
month or longer .
COLLISION PROCEDURE-ALL
SYSTEMS
Whenever a vehicle equipped with an air condi-
tioning unit is involved in a collision or wreck, it
AIR CONDITIONING SYSTEM
1- 6 7
should be inspected as soon as possible . The extent
or damage to any of all of the component parts and
the length of time the system has been exposed to the
atmosphere will determine the replacement of parts
and processing that will be required . The greater the
length of time of exposure to the atmosphere, the
greater will have been the chances for air, moisture
and dirt to have entered and damaged the system .
Every case may be entirely different so it is not possi-
ble to establish a hard and fast procedure to follow
each time . Good judgment must be used to deter-
mine what steps should be taken in each specific case .
The following procedure is presented as a guide
for use when inspecting a damaged vehicle equipped
with air conditioning .
1 . Remove the drive belt .
2 . Visually inspect the condenser, receiver-dehy-
drator, compressor, mounting brackets, conditioning
unit, all connecting lines and all controls to deter-
mine the extent and nature of the damage .
a. No repairs, such as soldering, welding or
brazing, should be attempted on the condenser be-
cause of its construction . If the vapor passages in the
horizontal tubes or return bends or manifolds have
been damaged in any way, the condenser should be
replaced with a new one.
b. The receiver-dehydrator should be re-
placed if there is any evidence of its having sustained
either internal damage or a fracture at any of the
lines or welded joints or if the system has been ex-
posed to the atmosphere for an undetermined period
of time .
c. Examine the compressor for any visible
external damage .
d. The evaporator should be examined for
damage and, if necessary, removed or replaced or the
entire unit processed where damaged or exposed to
the atmosphere .
e. All connecting lines and flexible hoses
should be examined throughout their entire length
for damage . If damaged in any manner, replace with
new lines.
f. Check all controls and connecting wires for
damage and replace with new parts where needed .
g. Check the clutch pulley for proper operat-
ion and freedom from damage .
3 . Install Charging Station.
4 . Purge the system .