Ok can't figure this one out. I have no heat and have troubleshooted a lot of things. First thing I noticed was the inlet to the heater core was out but not the outlet. So I flushed the heater core. Now both hoses are getting hot but still no heat. Blower motor is working, Car is coming up to correct temp. I have checked both air mix actuator and they are working fine. I tried the battery reset (pull the negative side for 5min). Still no heat just semi cool air. What am I missing?

Please tell us what year and model you have.

Sorry!

2000 Pontiac Bonneville SLE

Do you have automatic controls? Any problems with the temperature display showing the correct outside temperature? Could you see the actuators move?

Automatic Controls. No problems with the temp display. Yes I could see the actuators move. I took them off and turned the shaft by hand to see if it made a difference.

So, you manually moved the doors for the air mix on both the passenger and the driver'* side to full heat, and the symptoms are the same? That would rule out internal temperature sensors, sun load sensors, and the control unit. Not much left. Does the A/C compressor shut off when it should?

Yes I moved both sides and I also tried that actuator that changes the mode (floor, defrost, etc..) and they all worked fine. Yes the a/c compressor does shut off and the air is not cold but not hot. It is a very mild warm (if that makes sense). Not enough to heat it up when the temp. starts to drop.

I keep wondering if the coolant is actually running through the heater core or if there is enough pressure on the system for it to flow correctly.

Through your testing, you've pretty much ruled out everything but the heater core. Have you also checked to make sure the coolant level is proper? If it'* low, that could starve the heater core.

Actually Dick...he flushed the coolant and ruled out the core as well.

Foamy, is the air output good, just not warm enough? Do you have an air compressor where you could alternate between flushing with water, and then air?

Bill, I see that he flushed out the core - but don't see anything about flushing the coolant. With the actuators turned by hand to full heat, that rules out anything with the controls. I've had cores that would pass enough to warm the hoses, but not the air. If you have other ideas, post 'em up - because I'm running out of them.