Heater blows cool air at idle

[69thunderbird]

my heater does not blow warm air at idle, i could leave car running all day and heater would not blow warm air to melt ice on windshield.

after driving for 5-10 minutes heater will warm up but when i pull up to traffic light it begins to blow cool air again. the problem occurs at all fan (low, high, etc) and venting (floor,defrost, etc) options

noticed this intermittently in summer with AC too - of course with opposite affects, going from cold to hot, but random enough to not notice if it occured more at idle or while driving.

anyone else have this issue?

 

[sx sonic]

How's your coolant level?

 

[Blue hedgehog]

^ this.
When the coolant level drops, you can get an air pocket in the heater core. Higher engine RPMs will make coolant flow into the heater. When they drop again the coolant stops flowing, and the cold air comes back.

 

[69thunderbird]

coolant

i'll check the coolant level - guess if it's low, that will be the next problem to chase.

 

[Chevrolet Customer Care]

Hi 69thunderbird,

I’m sorry to hear of this concern with your heater. I cannot guarantee anything but I would like to take a further look into this for you. Please send a private message with your VIN, current mileage, preferred dealership and full contact information if any extra help is needed. I look forward to hear from you!

Kristen A.
Chevrolet Customer Care

 

[Sonic]

This is a known problem and is either or a combination of:

1) low coolant
2) bad thermostat
3) leaking/bad water pump

I am closing this due to the fact there are existing threads about this topic already. Call your dealership and tell them you have one or all three of the problems I listed and take the car in to be looked at.