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Pete, GMC Mechanic
Category: GMC
Satisfied Customers: 27814
Experience:  GM training and dealer tech for 14+ years. Diagnostics
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2007 GMC Yukon Denali the passenger side of the windshield

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2007 GMC Yukon Denali the passenger side of the windshield won't defrost or defogger but the driver side does fine

My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

This can be caused by a restriction in the defrost grille or heater box blocking flow to the passenger side defrost.On some models there are two mode doors for the defrost,one for the drivers side and one for the passenger side.If the passenger side mode actuator is faulty this can also cause this here.I would have the actuators checked/tested to see if any need replaced as well as the defrost grille checked to see if these are o.k.If these are all found to be o.k. then I suspect an internal blockage in the heater box itself with it needing possibly removed and then inspected and repaired.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Customer: replied 8 months ago.
Where is the pass defrost door solenoid?

Looking at your model here this one actually only uses one mode actuator.It is shown below.

If the air is blowing cold on the passenger side and warm on the drivers when defrost is on then the fault is with the temp actuator for the right side as shown below.If it is blowing warm but low or no air flow from the passenger side of the defrost then this usually indicates a restriction in the passenger side defrost grill or an issue in the heater box itself internally with a door that is stuck not opening properly and the heater box usually needs removed and taken apart for inspection and repair.

Let me know if you need anything else and feel free to rate my help here as this is how I receive credit for my time.Your 5 star rating is appreciated

Thanks Pete

Customer: replied 8 months ago.
It's not that it's cold, it's that it isn't blowing

I apologize for the delay.Since it is not blowing this usually indicates a broken door in the heater box or something fell into the defrost vent blocking flow or part of the interior heater box seal came apart in the heater box blocking flow.This would indicate the heater box usually needs taken apart for inspection and repair.

Thanks Pete

Customer: replied 8 months ago.
Just for clarification the drivers does blow, just not pass

Correct.Since there is only one mode actuator this indicates the mode actuator is working since the drivers side blows.The fault then is blockage or restriction in the heater box that is blocking air flow on the passenger side.The heater box usually needs removed and taken apart and repaired to resolve this here.

Thanks Pete

Customer: replied 8 months ago.
Removing the box is a big job isn't it?

Unfortunately on this model the entire dash has to be removed.You might see if you can remove the blower motor and any other bottom components from the heater box and get lucky and find a component jammed blocking air flow at the bottom of the heater box but if this is all found to be o.k. then the dash and heater box has to be removed.

Thanks Pete

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