2000 Silverado 1500

This has been happening for a while now. The temperature has to be below 30 degrees, then the heat/cool door will constantly open and close when it is set to hot. The control is turned all the way clockwise. But if you turn the knob 1/4 of a turn counter clockwise the door will stop banging. The only problem is that it will not happen if the temperature is at 35 degrees or above. I have not been able to figure this one out. It is a real PIA.

This has been happening for a while now. The temperature has to be below 30 degrees, then the heat/cool door will constantly open and close when it is set to hot. The control is turned all the way clockwise. But if you turn the knob 1/4 of a turn counter clockwise the door will stop banging. The only problem is that it will not happen if the temperature is at 35 degrees or above. I have not been able to figure this one out. It is a real PIA.

directly above the transmission interior hump is the location of this temp door ..remove assy and check for obstructions..in the ducting

When it is warmer I will take a look at the ducting for any obstructions.

I also have another annoying problem, at around 40mph the truck will surge. The rpm will go up and down maybe 100 RPMs and the speed will also move up and down maybe a half a mile an hour. I have replaced the fuel regulator about 2 years ago. The fuel filter has been replaced also. It is so much easier to work on the wife's truck. When it comes to oil changes and working under the truck. My pontiac is a real pia to do the oil changes.

When it is warmer I will take a look at the ducting for any obstructions.

I also have another annoying problem, at around 40mph the truck will surge. The rpm will go up and down maybe 100 RPMs and the speed will also move up and down maybe a half a mile an hour. I have replaced the fuel regulator about 2 years ago. The fuel filter has been replaced also. It is so much easier to work on the wife's truck. When it comes to oil changes and working under the truck. My pontiac is a real pia to do the oil changes.

your surges at 40mph may indicate a transmission problem. at this
speed the torque converter will engage this causes a 100rpm drop and a shift feel..If this is pronouced it may mean transfliud replacement ,and a plug change and wire resistance measurements.

this transmission fluid has changed it is now dextronVI.dextron III is bad for our transmissions as it does not flow properly and lubricate as it should ....GM put out a tsb about this in 2005...

how often and what transmission fluid do you use ?

transmission filter must be replaced also..

I usually change trans fluid every 50k. I need to change it again and also the trans filter. It is going to be in the 40's later in the week. I will get get a filter and pan gasket. As far as the fluid I used dextron VI, but i did not know that thanks for the update.