Repeat Rear Blower Motor Failure Or Inoperative - keywords AC climate gasket HVAC module processor resistor screw speed thermal

This PI was superseded to update model years. Please discard PIT3656.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

After replacing the rear HVAC blower motor processor (resistor), repeat failures have occurred. This concern may be caused by one of the following two items:

1. It has been noted when replacing this module, the "thermal gasket" that rests between the blower motor resistor and the HVAC case may fall off the HVAC case or the resistor. This thermal gasket is a thin square piece of aluminum (foil type) that mounts between the resistor and the HVAC case. With this gasket missing, the resistor temperature will raise until a thermal limit inside the module is reached. Then the resistor will default to an inoperative state. When the resistor lowers below its thermal state, the rear blower motor begins to operate again.
2. A second concern may occur when the screw(s) that retain the blower motor resistor are lost and a longer screw(s) are used as a replacement. If the screws are too long, the module will not apply enough pressure against the thermal gasket or make contact and the thermal gasket cannot dissipate the heat generated from the resistor.

To avoid this concern, follow eSI Document ID # 748863 completely.

1. Make sure that when removing the blower motor resistor from the HVAC case, the "thermal gasket" does not drop behind the HVAC case. When installing the blower motor processor, make sure the thermal gasket is installed between the blower processor module and the HVAC case. It will be necessary to apply the supplied grease to the gasket. The "thermal gasket" must be free of any dirt. If the thermal gasket is missing and cannot be found in the vehicle, a new blower motor resistor can be ordered and the new thermal gasket is packaged with the blower motor resistor.
2. If either of the retaining screws are lost, replace them with the exact length and diameter that was removed. If both screws are lost, it will be necessary to obtain the size and diameter screw from a like vehicle.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.