Pontiac Repair: 2005 Pontiac Montana sv6 rear blower problem, blower motor resistor, pontiac montana

Question
QUESTION: I have an 05 Pontiac Montana sv6 3.5L v6. I am having a problem with the rear blower unit. The blower runs on high all the time unless the fuse is pulled. Changing the front control has no effect on the the blower and the display for the fan on the rear entertainment center reads "disabled". I have already replaced the blower motor relay, which I really thought was going to take care of the issue. After finding a TSB online I have also checked the wiring under the passenger side and found no visible wire damage. Any other thoughts would be appreciated.

ANSWER: Hi Sean:

well this is a poretty complex system eve n know it doesn't seem that way. It can be an issue with either control head or the blower motor controler. if you unplug the rear control head does the motor continue to run? if so I would think that would eliminate an issue with the rear head it's self and that would narrow it down. If you had a true scan tool you could read the HVVAC control head (front) data and see if it indeed is trying to control the motor on at Hi speed all the time or not. The control head on that is programable I belive there was a service bulletin back in the day to address multiple issue but I do not remeber exactly what the issue it addressed were. My guess i not what you have going on but I'm not sure. did you try a used control head or a new one?

---------- FOLLOW-UP ----------

QUESTION: Thanks for your quick reply.  I realize that this is a complex issue. When you say "unplug the rear control head" are you talking about the whole rear entertainment system where the controls are?  If so, no, I have not unplugged that. The blower did stop when I unplugged the blower motor resistor, but I assume that's normal. From service records on the vehicle it appears that in 11/2003 there the "Vehicle entertainment wiring and/or connector repair or replacement (n6632)" as well as on 6/2007 there was "heater and air conditioning control replacement (D0362)".  So I'm not sure if I will be able to diagnose this problem apart from taking it to a dealer who has a computer and other diagnostic equipment seeing as the parts are not just cheap enough to swap out if I don't really know what the problem is. I have no problem doing the work I just need help diagnosing the issue.  Thanks for all your help to me and others it's a real blessing especially in times like these when people don't have as much to spend on vehicle maintenance.

Answer
Yes unplug the rear entertainment unit. that sends a signal through the front control head to run the rear fan. if you unplug the blower control module the fan will turn off that is what controls the fan speed from the signal of the control head (front). Those are warranty codes for specific repairs. I don't know how you could have had a 2003 date on a 2005 van. Those vans had all kinds of wierd issues with the rera enttertainmet unit the control head and the diaplay. That could have been a repair for the display not the control head. We had issues with the control head "wowing" and blinking in and out.