2004 Envoy xl Rear blower motor continues to run when turned off, runs full blast running or with ignition off, front switch has no effect, rear switch has no effect. pulled rear fuse, please advise on fix. poss rear blower resistor?
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The relay in your blower motor is stuck on, there is a TSB for this issue. Replace the blower motor resistor and you'll be back in business. How does the resistor get power if the fuse is pulled? Replacing the resistor will cure both problems. TSB is a technical service bullitin seen below Subject:HVAC Blower Motor May Run Continuously After Vehicle is Turned Off (Replace Blower Resistor Relay)Models:2004 Chevrolet Avalanche, Silverado, Suburban, Tahoe, TrailBlazer, TrailBlazer EXT2004 GMC Envoy, Envoy XL, Sierra, Yukon, Yukon XLwith Manual Control HVAC (RPO CJ3)Built Prior to August, 2003
Check the connection at the heater blower motor resistor.Wiggle or pull connector off and look for a melted pigtail these get very hot and usally are the cause of fan motor problems.Its located on passenger side of heat duct mounted with 2 screws.
Sounds like a "fan motor speed controller" or FMSC.
Either that module has gone out...or we're not getting the signal from the control panel sometimes called the EATC.
Lincoln has an EATC (for electronic air temp control)...GMC has something similar.
There is a way to run a diagnostic test of the EATC but am having trouble finding it for GM models.
If EATC test is done and fails...it will tell you it failed and would need replacing.
If EATC passes...it will tell you it passed and the fan motor speed controller would be at fault.
Usually, when a speed controller fails, the blower motor either doesn't turn OR it runs full blast.
Both parts EATC and the FMSC are expensive.
Since yours is running full blast...at least its providing air.
I'd try to run a diagnostic check to be for sure and maybe your parts might be less expensive and available at your local parts store.
Your problem is the Relay which is encased inside the Heater/AC Resistor Module. This is a very common problem with GMC and Chevy Trucks. The Relay's return spring fails and the relay is held closed by gravity. The only fix is to replace the Resistor Module. I have a 2004 Silverado and have replaced the Module 3 times and the Blower Motor twice. The Orange wire feeding the Module is always Hot (12V) and feeds the Relay Contact for Highest Blower Speed. Hence the Blower runs all the time even with the Key off and removed.
Service VME - HVAC Blower Continues To Run with Key Off
Some 2003 Full-Size Pickup / Utility A/C blower motor continues to run even when the key is removed from the ignition. The root cause is an internal failure within Linear Power Module ( LPM ) or also known as the Blower Motor Control Processor. The service fix is to replace the LPM (P/N 52495874).
I had the same thing on my 2004 Envoy and it was the blower motor resistor. Dealership wanted $240 to replace and I did it in 20 minutes for about $50. Bought the part at NAPA. I found out by searching on Google how to replace it. Hope this helps.
I had this same problem, With it running and heat and blower on full blast remove and unplug the rear faceplate for the rear heat.
Unplug for about a min.
Shut off engine.
Cycle the key 5 times.
Plug in the plug to the face plate.
For about a min. nothing will happen no heater no blower.
After the multiplex system refinds its address, the rear heat will then work again.
this worked for my 04 trailblazer.