My daughter has a 2002 blazer with about 42,000 miles. She came back from college for the weekend and on the way her heater seemed to blow cool air when she stopped at a town on the way. The next day while driving around town the "check guages"
light came on the the temperature guage showed hotter than normal. It then returned to normal. However, it seems that when she is stopped for any period of time the heater no longer blows warm air ( even stopped for a stop light) but when driving the heater seems to work normally. I haven't checked the coolant level or anything else yet ( as she is using the vehicle right now) but thought this was wierd enought that maybe someone here might be able to point me in the right direction to solve this.
Thanks in advance for any help.

 

She is now back an it does appear that the Dexcool level is low. No obvious evidence of a leak but low never the less.
Thanks for looking

 

Do you know if its throwing any codes? Thermostat may have to be replaced.

 

Sounds to me like she is low on coolant. Fill up the overflow tank, and watch it for the next few trips. Not that you have a leak, however as the air is bleed from the system it will replace it with coolant. Make sure the coolant level stays up in the overflow tank. Air does nasty things to Dexcool.

 

Reminds me of an old chevy van I owned. Hippy looking thing, shortbed, custom paint job and bed, oh well. When she started getting older she developed a leak that caused me to remember an even older way to check for level and condition of water. If it didnt blow hot air, it was low and i had to add some. Talk about lazy. Odd part was, I could never know for sure, cause it would go weeks with no problem and then all of a sudden be a little low.

Reason I remeberred that was because I am even older than that and before we all just filled our cars with something called "coolant", we simply used water. Up in the north country we would add antifreeze during the worst times. To make sure we actually had MOVING, thawed out water, we would also turn on the defroster as soon as we started the car and hope for a little temperature change (upwards) that indicated water was moving through the system. If it didnt go up slowly in the defrost (heater core)it (the engine)got real hot real quik cause the water was frozen. Shutting her down in time often thawed things out real good.


I agree it is low on water and a small leak may exist. That does not put the thermostat out of the question though. Keep a carefull eye on everything for a couple of weeks.