Heater problem
2005 Silverado V8 Two Wheel Drive Automatic 42000 miles

I have a 2005 Chevy Silverado that is having a problem with the blower control switch. The 5 speed went out first while 1 - 4 still worked. Then 4 went out. I still have 1-3. This all happened during the summer so I only noticed it with the AC. I recently turned on the heater and found that the blower only worked in 1 - 3 and the heater does not blow hot air consistently. It sometimes blows warm, then cold and the truck temperature also fluctuates from about 200 to 255. If I turn off the heat, back to cool, the vehicle temp goes back to 200 and stays there. I read that the blower resistor is a common problem and I have considered that, but the engine temp flux also has me concerned. Can the resistor cause that too? Its going to be getting cold soon, so any help would be greatly appreciated.
Jim

 

heater fan speed is the blower resistor; the temperature going to 255 is BAD thats an overheat condition, and the heat going in and out of warm air is a surefire sign of low coolant, or air pocket sin the coolant, when its cold, fill it, leave the cap off and run it until it goes into open loop, or full temperature, make sure its full then and cap it, call it good, check it next time its cold
should take care of that; might not hurt to check for coolant leaks

 

Ah, its amazing how we take new vehicles for granted. But its a new truck, how can it be low on coolant or have a leak? Well, yes, the coolant was very low, as were a few other fluids so check them all, causing air bubbles to flow through the system and causing it to overheat. After topping off the coolant, the problem went away. The fluctuating heating problem anyways. The blower motor resistor plug was indeed burned and needed to be replaced. Just for everyones info, dealer replacement resistors are about $65 while the replacement plug is $100 or more. I got one on line for about $20 so shop around. Luckily, it was a cheap fix and didnt result in any significant damage to the engine. I do have to find out where the coolant is going if it is in fact leaking because it is simply a time factor.