Diagnostic Procedure
*FRONT BLOWER RUNS AT ONLY ONE SPEED - DIAGNOSTIC PROCEDURE
| TEST | ACTION | APPLICABILITY |
|---|---|---|
| 1 | Turn the ignition off. Disconnect the Front Blower Power Module C1 harness connector. Disconnect the ATC C1 harness connector. Measure the resistance between ground and the Front Blower Motor Control circuit. Is the resistance below 10K ohms?
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All |
| 2 | Turn the ignition off. Reconnect all previously disconnected components. Connect the DRBIII® X10 Scope Probe CH7061 to the DRBIII®. Select the following from the DRBIII® 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® display. The voltage on the scope pattern 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® display the voltage range and duty cycle as described above?
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All |