10.8
FAN OPERATIONAL CONCERN (ON/OFF TYPE)
4. Measure resistance between auxiliary fan control wire and a good ground.
[a] If the measured resistance is greater than 1,000 , an open exists in the auxiliary
fan control wire, or auxiliary fan control is configured and not wired, or the switch
is bad. Repair open or replace the switch if an auxiliary fan control is used. If this
feature is not to be used, disable the auxiliary fan control with the programming
station. Refer to section 10.8.10.
[b] If the measured resistance is less than or equal to 1,000 , refer to section 10.8.9.
Perform the following steps to troubleshoot fan always on. The steps that led to this procedure do
not indicate a problem with the fan control logic in the ECM. The fan operation is normal if the
steps that you checked led you to this section.
10.8.6
Check for Output Open
Perform the following steps to check for an output open:
1. With ignition off, locate OEM supplied wire used for Fan Control #1.
2. Determine where the wire terminates. (e.g. fan solenoid, relay, data module, etc.)
3. Disconnect the Fan Control #1 wire at the solenoid/relay.
4. Turn ignition ON.
5. Measure resistance between the fan control #1 wire and a good ground, battery (-).
[a] If the measured resistance is greater than 48,000
or open, an open exists in the
FC#1 wire. Repair the open. Refer to section 10.8.10.
[b] If the measured resistance is less than or equal to 48,000 , refer to section 10.8.9.
10.8.7
Check for Output Short
Perform the following steps to check for an output short:
1. With ignition off, locate OEM supplied wire used for Fan Control #1.
2. Determine where the wire terminates. (e.g. fan solenoid, relay, data module, etc.)
3. Disconnect the Fan Control #1 wire at the solenoid/relay.
4. Measure resistance between the fan control #1 wire and a good ground, battery (-).
[a] If the measured resistance is greater than 1,000
or open, refer to section 10.8.9.
[b] If the measured resistance is less than or equal to 1,000 , the output wire is
shorted to ground, keeping the fan off. Repair the short or replace the wire.
Refer to section 10.8.10.
10.8.8
Check Override Request
Perform the following steps to check the fan override switch:
1. Is the fan override switch on?
All information subject to change without notice.
10-38
6SE497 9709 Copyright © 1997 DETROIT DIESEL CORPORATION
