I'm scheduled to drop my car again Monday, but...

While I drive my heater is great, but when I stop at a light the blower starts to blow cold. Once I start driving again it back to hot. Basically, I can't get heat while the car sits. Can anyone advise why this is happening so I can tell the dealer (who is clueless)?

 

You're probably low on coolant. Have you checked it?

 

I will now, but I checked it a week ago and it was fine and I had the problem then too.

 

Another alternative if the coolant level is fine is that the water pump itself is bad, or going bad.

 

Do you have the system on "auto" when this occurs or do you have it manually set to heat?

 

I tried both and it blew cold on both settings

 

Sounds like it has an air pocket.

That will cause the problems you are having. If it was a waterpump then the car would indeed overheat and very quickly I might add.

You can look at the heater hose on the passenger side near the firewall and there is a bleeder on it. Open it up (MAKE SURE THE CAR IS NOT HOT!!!!) and see if air comes out. If not then close the valve and start car and open it slowly.(Don't take the bleeder all the way out, just till the coolant starts to seep out.)Let some of the coolant come out and it should push the air out with it. Accelerate the engine 2000 to 3000 rpm rapidly and should push the air out. Close the valve. Repeat if necessary.