Heater works intermittently 98 Tahoe

[briantahoe]

Hey all,
Hope someone can help.This is the front section of the cab.
The heater blows cools air while idling ect., parked, stoplights. While driving the heater blows hot air for about 10 min, then it blows cool air. I turn off the heater, because it's not keeping the cab warm. It's cold outside and now getting cold inside. After a few minutes I turn the switch on for the heater and... nothing.
The blower isn't working, no hot air no cool air, nothing. After about 5 + minutes the heater turns on blowing hot air. For about another ten minutes. This cycle goes on and on. I've check the heater core under the dash and it's SUPER HOT to the touch. Just replaced the blower motor resister last night. Hope it prevents the blower from shutting down. Went on a small run, the heater blows hot air except when it's idling, stoplights, parking reading a map. Check the antifreeze and it full.
A couple of weeks ago went on a long ride and notice the temp gauge was dangeriously rising. Pull over to an auto store and filled up the radiator 50/50 dexcool. Thats it any ideas? thanks for your time and help.

 

[SunlitComet]

you need to look at the blower switch. beside controlling speed it controls weather or not the controller turns itself off and specifically moves actuators to certain positions as a result.

---------- Post added at 10:02 AM ---------- Previous post was at 10:01 AM ----------

when the off function is commanded by the switch certain things should disable themselves.

 

[briantahoe]

Thank You Sunlit Comet,
Went and purchased a heater blower switch today and I'm in the process of putting everything back together but from what I can tell the heater is BLASTING SUN HOT AIR! It's CRAZY hot, WOW! Almost passed out from the heat. LOL!
Going to drive up the snow cap mountains tomorrow for the final test, can't wait!
Hope that fixes it.
Thanks again for your response, Great Help!

 

[inthechateau]

I would have guessed the vac switch under the hood , but after he said teh core was hot it eleminated that suspect. Did not realize the switch did more than just kill the blower fan.

 

[SunlitComet]

should also add that when system is active. if the temp dial is in the max cold indentation water valve is commanded off. the whole rest of that dial will command open the water valve.