• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
Blower Motor Resistor Assembly B+ | 1 | 1 | -- | -- |
HVAC Control Assembly Ignition | 1 | 1 | -- | -- |
Blower Motor Control | 1 | 1 | 2 | -- |
Low Speed Control | 1 | 1 | 2 | -- |
Medium 1 Speed Control | 1 | 1 | 2 | -- |
Medium 2 Speed Control | 1 | 1 | 2 | -- |
High Speed Control | 1 | 1 | 2 | -- |
Blower Motor Resistor Assembly Ground | -- | 1 | 1 | -- |
Blower Motor Ground | 2 | 1 | 1 | -- |
1. Blower Motor Inoperative 2. Blower Motor Always On |
The HVAC control assembly applies voltage to the blower motor control circuit that corresponds to the selected blower speed. The resistors and the blower motor are in a series circuit. The following list represents the number of resistors in series with the blower motor per particular speed request:
• | Low speed-3 resistors |
• | Medium 1 speed-2 resistors |
• | Medium 2 speed-1 resistor |
When the operator requests High speed, the HVAC control assembly applies voltage to the blower motor through the high blower motor relay.
Control Module References for scan tool information
Ignition ON, mode selector set to Panel, cycle the blower motor from LOW to HIGH using the blower motor switch. The blower motor should operate in each speed position.
⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. |
⇒ | If the test lamp does not illuminate in each position, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control assembly. |
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
• | LOW - terminal E |
• | M1 - terminal D |
• | M2 - terminal F |
• | HIGH - terminal B |
⇒ | If the test lamp does not illuminate, test the appropriate control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control assembly. |
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the blower motor resistor assembly. |
⇒ | If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the blower motor resistor assembly. |
⇒ | If the test lamp illuminates but does not change intensity, test the control circuit for a short to voltage. If the circuit tests normal, replace the blower motor resistor assembly. |
⇒ | If the blower motor does not activate, replace the blower motor. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.