heater not working.
on 2004 Chevrolet Avalanche 1500

heater not working already replace thermostat. coolant has to be replenish every other day no leaks and no water in oil.

Asked by for the 2004 Chevrolet Avalanche 1500
there is a leak if you have to add. have a shop pressure check it for you.

1 more answer
I agree with Roy. You have coolant going somewhere. If the coolant level drops it creates an air pocket and can stop circulating to the heater core, causing the loss of heat. We would be happy to look at it for you. www.fenskiauto.com