Electrical Maintenance (Rev 1/99)
48
26. Turn variable resistance until the cab box shows “00”
degrees.
27. LEDs PL3 and 6 should light.
28. Turn the variable resistance until the cab box shows
“-05” degrees.
29. LEDs PL3, 4, and 6 should light as well as the top left
LED in the cab box display.
30. Turn off the cab box and power supply. Move jumpers
on W1 and W2 to the opposite positions. Turn R16 to
position #3.
This test will checkout most circuits on the board. It will not
test a circuit that may be broken or burned out between the
relays and all the connector pins that were not connected to
in this test. To test these, a volt meter or external lights
would have to be connected to each pin and observed for the
proper results.
P.C. Board P/N 41-1812 and P/N 41-1619
Test Procedure
1. Connect a 12 volt DC power supply, positive to GS1
stud hole (2 circuit) and negative to GS3 stud hole (CH
circuit).
2. Connect 12 volt positive to pin 1 of connector P6 (ACD
circuit).
3. Connect pin 3 and pin 5 of connector P4 together (this
connects 12 to CH).
4. Connect pin 1 of connector P2 and pin 1 of connector
P4 together (this connects 8B to 8HA).
5. Plug the cab box into the P.C. board with the cab box
harness.
6. Connect a variable resistance (620 to 1200 ohms) to the
two pin connector on the cab box harness (this simu-
lates the thermostat sensor).
7. Plug in the six relays as specified on the board.
8. Replace any fuses that are missing or blown.
9. With the power supply turned on and the cab box
turned off, PL3 only should light.
10. Turn cab box on and turn the setpoint to “00” degrees.
11. Turn the variable resistance until the cab box shows
“05” degrees.
12. LEDs PL1, 2, 3, 5, 8, and 11 should light as well as the
LED in the cab box display between the digits at the top
of the display and the snowflake LED.
13. Turn variable resistance until the cab box shows “00”
degrees.
14. All LEDs except PL3 should go off.
15. Turn the variable resistance until the cab box shows
“-05” degrees.
16. LEDs PL1, 2, 3, 5, and 9 should light as well as the
LED in the cab box display to the top left of the digits.
17. Move the jumpers from W3 and W4 to W1 and W2
positions and turn R17 fully counter clockwise.
18. Turn the variable resistance until the cab box shows
“05” degrees.
19. In about 1 minute the circuit should go into the defrost
mode. In this mode LEDs PL3, 7, 8, and 11 should light
as well as the defrost indicator on the cab box.
20. In another minute and 15 seconds the circuit should
come out of the defrost mode. LEDs PL1, 2, 3, 5, 8, and
11 should light.
21. Turn cab box and power supply off.
22. Disconnect pin 1 of connector P6 from the positive side
of the power supply. Connect pin 4 (or 5) of connector
P5 and stud hole GS2 to positive.
23. Turn power supply and cab box on.
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