Q: Vents blowing cold Air. Heat inop.

asked by on December 16, 2016

Denali had cold air blowing from the vents when heat was on. REplaced thermostat flushed rad and heater core and lines. Still blowing cold air. Checked Damper door by the glove box, I can move it manually but just changes the air flow from blowing by your feet to blowing out the defrost vents. I'm wondering where the Temp blend door is and if something is wrong with it?

My car has 87000 miles.
My car has an automatic transmission.

Heater is not working Inspection $79.99 - $89.99 Get a Quote

Hey there:

If your engine is not overheating and you’ve flushed the core and coolant correctly, it’s possible that you may have an electrical issue causing the heater to not function correctly. I’d start by checking fuses and relays powering the heater core first before you begin to remove components. If the issue does not clear up after checking electrical, there may be a problem with your heater controls. You might want to purchase a service manual for your 2003 GMC to get specific locations of all control vents before you remove the dash; as it’s very complex under there and can be difficult to repair and replace. If you’d like to have a professional mobile mechanic assist you, contact our team and set up a heater is not working inspection.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

What others are asking

A mechanic says I need tie rods, gave weird estimate I think

To perform an alignment, there can't be any "excess" wear in the suspension simply because the tolerances in an alignment are very tiny. If there is wear, as you try to adjust and set the alignment, the suspension simply moves...

engine has developed a high pitched whine sound

Hi there. Usually a high pitched sound as you are describing is caused by a bearing, pulley or belt that is worn out. Since there are multiple possible sources under the hood of your vehicle that could cause this noise,...

Ok i had to replace my car battery for my 2003 vw beetle it cranks over but wont start so i check the oil i put a quart in it

Be sure the battery is actually fully charged and securely connected with no corrosion on the terminals. Confirm that the engine immobilizer system (security system) is not activated thus preventing the car from starting. If the immobilizer system is on,...

Engine knocking noise in 2003 Honda Civic

A knocking noise is never a good sign on an engine. If the sound appears once, then the engine is started and gets louder when you rev the engine then it may be a rod knock meaning that the engine...

My landrover discovery is extremely bouncy at random times. I was told I needed my abs sensor replaced so I did so. The bounce has

Some of the Disco's were equipped with an optional air suspension system. The system works well for the first few years, but once it starts giving problems, it quickly becomes an expensive nightmare. Converting it to a standard spring-shock absorber...

My 2009 GMC Sierra is making a clunking noise in the rear end. It happens when the truck is in Drive, but while I am applying the

It is possible that you could have a loose leaf spring shackle causing this noise. If the truck does not have leaf springs on the axle does possible that it has an arm that acts as a control arm that...

My car wont go above 40 mph,has a burning smell,and has a noise?

Hi There, What you are describing sounds like you may have a clogged catalytic converter. The catalytic converter converts toxic exhaust gases into less harmful pollutants that are suitable to be expelled into the atmosphere. When the catalytic converter is...

My truck struggles to start and stay running

This sounds like a fuel pump that is weak to start the vehicle and then stops pumping after ten minutes when it heats up. Have the fuel pressure checked to see if it is holding pressure and keeps pressure when...

No fuel flow from tank

It sounds like you may have a faulty fuel pump or a bad fuel pump relay. The relay wires should have ground on two wires, power on one wire and switched power on another wire. To activate the fuel pump...

Related articles

A Buyer's Guide to the 2012 GMC Yukon Hybrid
The The GMC Yukon is about as big and powerful as any SUV can ever get. However, in the past, that also meant paying a large sum every time you hit the pump. GMC has addressed this problem with their...
How to Get GMC Dealership Certified
GMC car dealerships offer automotive technician jobs to mechanics who are certified through one of the many programs they have available.
A Buyer’s Guide to the 2012 GMC Canyon
In In today’s world where it seems as if carmakers are determined to deliver only the largest vehicles possible, the 2012 GMC Canyon offers a compact pickup that holds its own. From a 4-cylinder that offers more horsepower than other...