Heater/blower Won't Shut Off

George.501Blues · January 11, 2008

I have a 2003 GMC Sierra and just today when I shut my vehicle off I noticed the heater was still moving air. At first I thought this might be normal and it would shut off after a slight delay. However, once I pushed the power button on the heater the blower still continued to run. I waited in the truck to see if it would shut off but in still continued to run. I check the web to see if I could find a solution and stumbled upon a site which told another user to try pulling the fuse. I tracked down the fuse and pulled it, which did stop the blower, but when I put the fuse back in the blower kicked in again. I tried disconnecting the battery and pulling the HVAC fuse but the blower still runs. I check this websites for answers and it looks like it could be anything from faulty wiring to the heater controls. Just wanted to see if anyone has run into this problem before. Any ideals on how to diagnose this problem. It is winter here in Alaska (right around 10 degrees) and without a heater it could be rather unconfortable. Thanks in advance.

pwall · January 11, 2008

HI.

I had the exact same issue in my truck about a month or so ago. It was the heater control module.

It cost me @ $400 to have it fixed at the dealership (part alone was $250).

GMTRUCKTECH · January 11, 2008

Your blower motor resistor is shorted replace it. It's located under pass side of dash right next to blower motor.

George.501Blues · January 12, 2008

I just wanted to say thanks to both of you for answering my questions. It was the the blower resistor and cost me about $98.00 just in case anyone was wondering. I replaced it myself and it was fairly easy.

George.501Blues · January 11, 2008

First thanks for replying back so quickly.

Second I see I got two different areas to check, the blower motor resistor or the heater control module. The question is how can I tell which one to replace?

Here some more information regarding the issue. I have no control of the fan speed as it appears to be somewhere between high and low. I can not power off the heater/AC unless I pull the fuse. The rest of the heater module appears to be working as I can still get defrost/floor and vents to move air. I would assume I would need a professional to fix the heater control module, but what about the blower motor resistor? Is this something an average joe could do?

Thanks again for your help and input.

pwall · January 11, 2008

This might help.....when the heater control module went out, I could not control anything.....vents, fan speed, temperature, etc. It was full-blast, full heat, all vents.

GMTRUCKTECH · January 11, 2008

Found some bull's that may help you.

Subject:Front Blower Motor Inoperative or May Not Shut Off In Extremely Low Ambient Temperature Conditions (Replace Blower Motor Control Module) #06-01-39-002B - (04/12/2007)

Models:2004-2007 Buick Rainier

2004-2006 Cadillac Escalade Models

2004-2006 Chevrolet Avalanche, Silverado, Suburban, Tahoe

2004-2007 Chevrolet TrailBlazer Models

2007 Chevrolet Silverado (Classic)

2004-2006 GMC Sierra Models, Yukon Models

2004-2007 GMC Envoy Models

2007 GMC Sierra (Classic)

2004-2006 HUMMER H2 Models

with Automatic Temperature Control HVAC System (RPO CJ2)

This bulletin is being revised to include the 2007 Silverado/Sierra (Classic) and midsize utility models. Please discard Corporate Bulletin Number 06-01-39-002A (Section 01 -- HVAC).

Condition

Some customers may comment that the front blower motor is inoperative or continues to run after the vehicle has been shut off.

Cause

These conditions may be caused by a blower motor control module failure. This failure will only occur when the vehicle is operated in ambient temperature conditions of -23°C (-10°F) or below. GM expects most failures to occur in Alaska or northern Canada. Dealers outside of the regions where extremely cold temperatures are encountered should NOT order the part listed below. Dealers outside of cold weather regions that install this part will be subject to warranty claim review.

Correction

Important: Replace the blower motor control module ONLY if the vehicle experienced a blower motor control module failure in extremely cold ambient temperature conditions. This information DOES NOT apply to any other blower motor conditions.

Technicians are to replace the blower motor control module, also called the Linear Power Module (LPM), with the P/N listed below. Refer to either the Blower Motor Control Processor Replacement or Blower Motor Processor Replacement-Auxiliary procedures in SI. After replacement of the blower motor control module, the customer may notice a slightly higher than expected blower motor speed at any of the blower speed settings.

Parts Information

Part Number

Description

Qty

89018849

Module Assembly, Auxiliary Blower Motor Control (Rear System on Escalade ESV, Suburban, Yukon XL)

1

89018964

Module, HTR & BLO & A/C CONT (Front system only vehicles - Except H2)

1

89023355

Module Assembly, Blower Motor Control (H2 models)

1

89024926

Module Assembly, Auxiliary Heater & A/C Control (Rear System on Escalade, Yukon, Tahoe)

1

Warranty Information

For vehicles repaired under warranty, use:

Labor Operation

Description

Labor Time

D0890

Module, Blower Motor Control - Replace

Use Published Labor Operation Time

Add

Diagnostic Time

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

Subject:Blower Motor Operates on High Only or Repeat Blower Resistor Failure - kw GMT800 GMT805 GMT820 GMT830 AC heater heat front air manual HVAC electrical wire high inoperative speed #PIT3081 - (07/22/2004)

Models:.

The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.

Condition/Concern:

Customers may comment that the A/C blower only operates on high or repeat blower resistor failures. Cause is a mis-positioned harness from the blower motor assembly to the right I/P fuse block C4 causing harness rub through at right I/P metal support.

Recommendation/Instructions:

Repair wiring and reposition blower motor harness away from the right I/P support. You may also want to insulate the I/P support bracket with foam tape to prevent any future concerns. Refer to SI Document 885398 for further details on wiring schematics for this circuit.

.

Please follow this diagnosis 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. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.

Models:

(03-05 Chevrolet All Full Size Trucks And Utilities) and (03-05 GMC All Full Size Trucks and Utilities)

.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION