I have a 2001 Silverado 1500 2WD with a 4.8 liter V8. The heater will only blow luke warm air. Radiator is full of fluid, and I also changed the thermostat. Engine is running at the appropriate 200 degrees, but not hot air. Any ideas on what might be causing the heater not to blow out hot air?

Thank you

 

Usually it is a bad blend door actuator. It is under the dash on the passenger side. Another possible cause is a clogged heater core. With the engine at operating temperature lightly touch both heater hoses. If they are both hot then the core is not clogged, but if one is much hotter than the other, the core is clogged.

 

I had the same problem with my 99 and it was a clogged heater core and if this is your problem it can be fixed pretty simply. They usually get clogged just from debris like rust chips and stuff. All you have to do is disconnect the hoses from the firewall( be careful not to break the connection or anything), they should pop off pretty easily with a little wiggling. Take a water hose and shoot water into the left side(left if your looking at the front of truck) and it should clean off all the debris that is on the heater core. It should come out the other side with all the debris and you're done when it looks like the water is flowing pretty easily. When you are done connecting the hoses all back together drive your truck until its at operating temp and when you turn on your heater it should be nice and hot. I hope I was detailed enough and helps so you can your heater going again.

 

Thank you for the information. Can you tell me exactly where under the passenger side dash I can find the "blend door actuator"? Does this part typically need replaced, lubricated,...

 

The blend door actuator typically does go bad. Under the dash on the passenger side there is a cover that needs to be removed. I believe there are 2 screws to remove. With this panel removed it is easy to see it. They are all plastic with plastic gears and tend to go bad.

 

There's also another one on the driver side, tucked up under the wiring by the gas pedal. I'd try unclogging the heater core first honestly. Get it up to operating temp and see if one hose is hotter than the other, if it is then put a water hose on it and unclog it. If that doesn't do the trick then replace the blend door. Recently did both of these on mine. Only needed to unclog the heater core but already bought the actuator so I put it on too. While you're in there, if you haven't done it before, replace the 2 cabin air filters.

 

bought a 2004 and the passager side is very hot but I have to turn the heat on the driver side full blast to get hot air out of it. Any ideas?