TEST
ACTION
APPLICABILITY
2
Turn the ignition off.
Reconnect all previously disconnected components.
Connect the 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.
Set the time to 10ms/Div.
Set the voltage range to +20.0v.
Set the offset to 4.00v.
Set the Probe to X10.
Start the engine.
Press the ATC’s PWR switch on.
Using the X10 Scope Probe, back probe the Front Blower Motor Control circuit in the
Front Blower Power Module C1 harness connector.
NOTE: The Blower Power Module provides a 12.0 volt signal to the ATC over
the Front Blower Motor Control circuit. The ATC provides a variable duty
cycle ground to the 12.0 volt signal based on input from the Front Blower
Speed Control switch.
NOTE: When the blower speed is set to low, the ATC Module provides a short
duty cycle (less time grounding the signal voltage).
NOTE: As higher blower speeds are requested, the ATC Module increases
the duty cycle (more time grounding the signal voltage).
NOTE: When the highest blower speed is requested, the duty cycle increases
to where the signal pattern is almost a flat line (with brief voltage spikes).
Set the blower speed to low, then slowly raise the blower speed to high while
observing the DRBIII
t display.
The voltage on the scope patten should cycle from approximately 0 volts (duty cycle
on) to 12.0 volts (duty cycle off) for all blower speeds.
The duty cycle pattern should change smoothly as the blower speed changes from low
to high.
Does the DRBIII
t display the voltage range and duty cycle as described above?
All
Yes
→ Replace the Front Blower Power Module 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.
645
HEATING & A/C
*FRONT BLOWER RUNS AT ONLY ONE SPEED - ATC —
Continued