heater blowing luke warm air - the heat only blows luke warm air. i changed the thermostat already and going to have the coolant reversed flushed. any other ideas??

the heat only blows luke warm air. i changed the thermostat already and going to have the coolant reversed flushed. any other ideas??

Based on what you're saying my first thought would be the heater core is clogged or simply shot.

thats what i was thinking about being clogged because if it was shot wouldnt it not blow any heat, im trying to think of all solutions before starting the 8hrs or so do change the core

jguzzier1999 wrote:thats what i was thinking about being clogged because if it was shot wouldnt it not blow any heat, im trying to think of all solutions before starting the 8hrs or so do change the core

They do occasionally have intermittent failure, like a light bulb that flickers but it’s more likely packed with gunk and often that gunk is corrosion you’ll have a hard time at best getting out.

Definitely worth trying a hard flush to see what happens.

Yes, get it flushed first. GM's are know to get air trapped in system. This will cause heater core to only get warm, not hot. System needs to be burped system.

one way to tell if the heater core is clogged is to grab the two hoses that feed into the firewall and feel if there is a difference in temp. should not be much of a difference if the core is flowing properly.

if you think there is air in the system try removing the overflow tank cap *while the engine is cold* then turn the engine on and let it run for a few minutes. this will help the air bubbles flow through the system and out the overflow tank
(assuming you have the same pressurized overflow tank as they started using in 1999).

thanks for the replys will be doing tomorrow fun day ahead

Have you checked to make sure the blend door is moving all the way to "hot"?

How do you check if the blend door is moving all the way to hot?

I would listen to see if you can hear the door moving at all when you change the heat settings. You will have to listen closely, with the blower on it's slowest speed. The blend door actuators are known to go bad. That would cause the blend door to become fixed in one location, which could be at a "warm" setting (allowing both cool and warm air into the cab, making the air only luke warm.