I have a 92 bonneville and for some reason the heat works somes times but rarely. If the car is already hot and i turn on the car, the heat starts to work but then within a minute it blows out cold air. Right before cold air comes out, the electronic temp. display flashes. I have replaced the thermostat and am not sure what to do from here. Any help would be appreciated, thank you.

Hmm,
When is the last time the coolant was changed? We could start with that basic.
I'm worried that the heater core is shot?? You would see antifreeze leaking into the cabin if that was the case. Maybe a blockage somewhere in the coolant system??

Adam

i havent changed the coolant since i have had the car. i know the person that had it got a tune up for it (4-5 years ago). I'm gonna flush the coolant sytem and chech that. I dont see any leaking anti-freeze so hopefully it'* not the heater core. In my car the climate control is all electronic and i noticed that when it does begin to blow out cold air the set temp. Flashes.

I did a coolant flush but the heat still does not work. I talked to a mechaniche gave a few things that could be wrong. BCM malfunctio, defective climate control console, or blend door inop.