Problem:Compressor Clutch Inoperative - (Pages 7, 8, 9, 10 and 11)626 Diesel
Test Conditions: (1) Key at "ON" (Engine off)(2) Fan switch at "1"
(3) A/C switch "ON"
Note: Air should flow from outlets. If no air flow, see Blower Motor Inoperative (626 FWD) in the 1983 Technical & Troubleshooting Manual before proceeding.
MANIFOLD GAUGE SET:
Step 1. Connect a manifold gauge set to the service valves and observe the refrigerant pressure.
Note: The ambient temperature must be 32~F (0~C) or above.
CHECKING RESULTS
A. If the refrigerant pressure is below 30 +/- 3 PSI (2.11 kg/sq.cm) check the system for a refrigerant leak.
B. If the refrigerant pressure is above 30 +/- 3 PSI (2.11 kg/sq.cm) proceed to Step 2.
FUSE BLOCK:
Step 2. Check the following (4) fuses and then proceed to Step 3.
FUSE NAME AMP
Air Cond. 15
Meter 10
Cooling Fan 20
Audio 15
Use the designated fuse if blown.
AIR CONDITIONER SWITCH CONNECTOR:
Step 3. Check the blue-yellow and both blue wires for power at the A/C switch connector.
CHECKING RESULTS
A. If all wires have power and the indicator light is on, proceed to Step 5.
B. If all wires have power and the indicator light is not on, proceed to Step 4.
C. If power exists in only the blue-yellow wire, replace the A/C switch.
D. If no power exists in the blue-yellow wire, check for a loss of continuity between the 15 AMP fuse marked "Audio" and the A/C switch connector.
A/C SWITCH CONNECTOR:
Step 4. Ground the blue-red wire at the A/C switch connector.
CHECKING RESULTS
A. If the indicator light does not come on replace the indicator bulb.
B. If the indicator light comes on, check the bluered wire for a loss of continuity between the blower resistor and A/C switch connector.
Note: The compressor clutch should operate even though the indicator light does not come on. After repairing the indicator light problem proceed to Step 5.
TERMINAL #6 A/C CONTROL BOX:
Step 5. Check the blue-green wire for power at the A/C control box (Terminal #6).
CHECKING RESULTS
A. If power exists, proceed to Step 11.
B. If no power exists, proceed to Step 6.
TERMINAL #3 A/C CONTROL BOX:
Step 6. Check the blue wire for power at the A/C control box (Terminal #3).
CHECKING RESULTS
A. If power exists, proceed to Step 7.
B. If no power exists, check the blue wire for a loss of continuity between the A/C switch and the A/C control box.
CHECKING BLUE-GREEN WIRE AT A/C CONTROL BOX:
Step 7. Check the blue-green wire for power at the A/C control box (Terminal #8).
CHECKING RESULTS
A. If power exists, proceed to Step 8.
B. If no power exists, check the blue-green wire for a loss of continuity between the 15 AMP fuse marked "Air Cond." and the A/C control box.
COLOR CODE FOR CONTROL BOX:
Note: The following color code changes between the "Air Cond." fuse and the A/C control box.
YELLOW WIRE, CHECK FOR POWER AT A/C CONTROL BOX:
Step 8. Check the yellow wire for power at the A/C control box (Terminal #9).
CHECKING RESULTS
A. If power exists, proceed to Step 9.
B. If no power exists, check the yellow wire for a loss of continuity between the 20 AMP fuse marked "Cooling Fan" and the A/C control box.
TERMINAL #5, CHECK AT A/C CONTROL BOX:
Step 9. Ground the blue-red wire at the A/C control box (Terminal #5).
CHECKING RESULTS
A. If the compressor clutch engages, check the blue-red wire for a loss of continuity between the blower resistor and the A/C control box.
B. If the compressor clutch does not engage, proceed to Step 10.
JUMPER WIRE ACROSS BLACK WIRES AT A/C CONTROL BOX:
Step 10. Use a jumper wire across both black wires at the A/C control box (Terminals 1 & 7).
CHECKING RESULTS
A. If the compressor clutch does not engage, replace the A/C control box.
B. If the compressor clutch engages, check both black wires for a loss of continuity between thermistor probe and A/C control box (Terminals 1 & 7). Also check the black wire for a loss of continuity between ground and A/C control box (Terminal #7). If continuity exists in the above black wires, follow the (4) steps below in order to troubleshoot the thermistor.
CHECKING THERMISTOR RESISTANCE:
RESISTANCE CHECK:
(1) Remove the wire connector from thermistor.
(2) Connect an ohm meter to the thermistor terminals in order to check if the resistance falls within the two lines in the graph below.
NOTE: The temperature inside evaporator should be the same as ambient temperature when checking resistance.
(3) If the checked point is within the two lines, the thermistor is normal.
(4) If not, the thermistor is defective and must be replaced.
CHECK FOR POWER AT COMPRESSOR CLUTCH CONNECTOR:
Step 11. Check the blue-green wire for power at the compressor clutch connector.
CHECKING RESULTS
A. If no power exists, proceed to Step 12.
B. If power exists, repair or replace the magnetic coil.
JUMPER WIRE LOCATION:
Step 12. Remove the boot connector at low pressure switch and use a jumper wire to jump across both terminals of the boot connector.
CHECKING RESULTS
A. If the compressor clutch does not engage, check for a loss of continuity in the blue-green wire between low pressure boot connector and compressor clutch connector. Also, check the blue-green wire for a loss of continuity between A/C control box (Terminal #6) and low pressure switch boot connector.
LOW PRESSURE SWITCH CHECK:
B. If the compressor clutch engages, follow the
(3) steps below in order to troubleshoot the low pressure switch.
(1) Unplug the connector from low pressure switch.
(2) Use an ohmmeter to check low pressure switch terminal for continuity.
(3) If no continuity exists, the low pressure switch is defective and must be replaced.