[GMC/Jeep]

I just bought a 2000 GMC 1500 3 weeks ago, heater worked great. I had surgery on my ankle and the truck sat for 2 weeks while I was on crutches. Well my wife took the truck to get straw the other day and about melted the heater was working great, the next day I drove it same thing. Drove to work yesterday and was very chilly, I could only feel heat comming out while the blower was on number 2 setting. On the way home this morning just enough heat to defrost the windows. I've checked the heater hoses-both are warm, so I'm ruling out the core for right now. Any ideas?

 

[ChevyFan]

I just bought a 2000 GMC 1500 3 weeks ago, heater worked great. I had surgery on my ankle and the truck sat for 2 weeks while I was on crutches. Well my wife took the truck to get straw the other day and about melted the heater was working great, the next day I drove it same thing. Drove to work yesterday and was very chilly, I could only feel heat comming out while the blower was on number 2 setting. On the way home this morning just enough heat to defrost the windows. I've checked the heater hoses-both are warm, so I'm ruling out the core for right now. Any ideas?

How many miles on it? I think someone else had this issue recently, where the heater core seemed to be functioning properly in and out, something to do with the fan itself? Anyone recall that conversation?

 

[GMC/Jeep]

The truck only has 70,000 miles on it. The fan works on all settings and power levels, the heat output just changes from day to day. I had read on another site about an actuator under the dash somewhere that controls the door for the heat out put from the core-anyone know where it is for sure or a possibility?

 

[collinsperformance]

maybe a bad blend door or resistor?.....mike

 

[ChevyTech]

I agree check to see if the blend door motor is functioning and the go after the resistor. Typically if the resistor is going bad you lose fan speeds but you never know.