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Pete, Pontiac Technician
Category: Pontiac
Satisfied Customers: 27833
Experience:  17 Years Pontiac Technician and training.
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2007 grand prix with 3800 engine, heater temp is cold

Customer Question

2007 grand prix with 3800 engine, heater temp is cold sometimes and warm other times. Blower works fine.
Submitted: 1 year ago.
Category: Pontiac
Expert:  Pete replied 1 year ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

With the engine running and warmed up fully and heater set to hot air and turned on feel the heater core hoses leading to the heater core under the hood at the firewall.Both hoses should be very warm to hot to the touch and right at the same temp.If you have one that is very warm or hot and the other is allot cooler this indicates that the heater core is restricted.

From here you can try and flush it out by removing the heater core hoses from the heater core and clamp off the hoses.Then take a garden hose and flush one end of the core until the flow is clear and free moving and then flush the other end.Once this is done reattach the heater core hoses and run the engine topping off the coolant level.If the heater works then the issue is resolved.If one hose is still hot and the other allot cooler then the heater core will need replaced unfortunately.

If both hoses are hot and you do have good air flow from the fan inside the car but cool to cold air most of the time this can indicate the hot/cold temperature actuator on the heater box is faulty and needs replaced.This is most common next to a restricted heater core.This would need to be tested further to be sure but is usually the cause here.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.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