GMC 1976 ZEO 6083 Maintenance Manual page 749

24E- 10 ROOF MOUNTED AIR CONDITIONER
REFRIGERATION SYSTEM DIAGNOSIS
AIR CONDITIONER FAILS TO COOL
lead with the black tip goes to it . The start
capacitor is checked with the tester switch in
position "A" ; a run or fan motor capacitor in "B".
Plug the tester into any 120 volt source . Push the
button down and look at the light on top of the
tester . If the capacitor is good the light will
flash off and on . If the light stays on it indi-
cates a short; if it flickers it indicates a leak ;
replace the capacitor.
2. Start Relay 2 . Remove leads and check with ohmmeter for con-
tinuity between start winding terminal and start
capacitor terminal . If the contacts are open, re-
place the relay. Clip amprobe around lead to the
start capacitor. Start the compressor. It should
show two or three amps for only a couple of sec-
onds, then zero current when the relay cuts out.
If current continues after the compressor starts,
replace relay.
Problem Remedy
1 . Compressor starts and runs .
1 . If the compressor starts and runs then the
problem is in the refrigeration system and more
checks can be made . If the compressor fails to
start and/or run steadily, check the electrical
system .
2. Temperature check. 2. Place a good refrigeration thermometer close
to the center on both the return and blower sides
of the evaporator . If the temperature difference
is from 18 to 23°F . (9 to 13°C .), the system
is okay . It is cooling the air as much as it can .
If the temperature difference is less than 18°F .
(9° C.), check further before opening the refrig-
eration system .
3. Clean components, fan motor 3. Clean any dirt or obstructions that may effect
rotation .
the operation of the air filter, blower wheel, and
evaporator fins . Check fan motor rotation . Blower
should pull air through evaporator without
obstruction .
4. Leaks o_ r kinks 4. Inspect coils, lines, and connections for pinch,
kink, or obvious leak indicated by compressor oil.
5. Capillary tube obstruction 5. Feel along the capillary tube for a temperature
(figure 13). change . It should be the same temperature at both
ends . If not, it is restricted, and must be
replaced .