TEST
ACTION
APPLICABILITY
7
Turn the ignition off.
Disconnect the ATC C2 harness connector.
Disconnect the Rear Booster Fan Rear Control Switch harness connector.
Measure the resistance of the Rear Fan Sense Return circuit between the ATC C2
harness connector and the Rear Booster Fan Rear Control Switch harness connector.
Is the resistance below 5.0 ohms?
All
Yes
→ Go To 8
No
→ Repair the Rear Fan Sense Return circuit for an open.
Perform BODY VERIFICATION TEST - VER 1.
8
Turn the ignition off.
Reconnect all previously disconnected components.
Connect DRBIII
t X10 Scope Probe CH7061 to the DRBIIIt.
Select the following from the DRBIII
t menu: PEP Module Tools; Lab Scope; Live
Data; and Lab Scope.
Select the following Lab Scope settings:
Set the time to 10ms/Div.
Set the voltage range to +10.0v.
Set the Offset to 2.00v.
Set the Probe to X10.
Start the engine.
Press the ATC’s PWR switch on.
Press the REAR fan mode switch on, so that it is in manual mode. The word
9REAR9
should display on the ATC display panel. The word
9AUTO9 should not be displayed.
Turn the Rear Booster Fan Rear Control Switch to the AUTO position.
Using the X10 Scope Probe, back probe the Rear Fan Sense circuit in the Rear
Booster Fan Rear Control Switch harness connector.
Slowly turn the Rear Booster Fan Rear Control through each of the 12 switch
positions (Auto, Off, & Spds 1 - 10) while observing the DRBIII
t display. The voltage
should increase gradually from approx. 0.06 to 4.9 volts with no spikes or signal drop
out.
Was any loss of signal observed while rotating the switch?
All
Yes
→ Replace the Rear Booster Fan Rear Control Switch in accordance
with the Service Information.
Perform BODY VERIFICATION TEST - VER 1.
No
→ Replace the Automatic Temperature Control (ATC) in accordance
with the Service Information.
Perform BODY VERIFICATION TEST - VER 1.
609
HEATING & A/C
REAR FAN POT OPEN (ACTIVE) - ATC —
Continued