2000 tahoe heat problem

I have a 2000 tahoe with manual heat controls. After driving for 2 hours straight the panel becomes inop if the temp control is on max, no matter the mode or fan position. If I stop for 20 minutes it works fine and will not act up for two or three months. Any help would be appreciated.

Same thing happened to mine. EXACT symptoms. I had mine fixed at the dealer and it was a blend valve not working. They told me it had to be replaced and it has worked since.

Recently my rear heat does not work. It never warms up. Seems another sticky blend valve but this time "really stuck" and in the cold position. I am going to pull it apart later today.

I have the exact same problem. If you are not paying attention, you will flat out get roasted when it gets stuck like this. I just recently made a trip and made sure the temp setting did not go over midway to keep this from happening. Worked fine this way, but I would still like to have the problem fixed.

Where exactly is this blend valve located? Is it in the engine compartment or is it located behind the control panel?

The blend door motor is located on the passenger side under the dash and the 5mm bolts(2) point straight at the floorboard.Take the insulator panel off under the glove box(3 7mm screws) and you will see the little black motor almost against the firewall. EASY fix. I also went ahead and replaced the a/c control panel to prevent any further problems or possibility of problems on the next trip. 2 minutes is all it takes to replace so don't let anyone charge you an arm and a leg and a kidney and a car payment,etc...to replace this.My total bill for factory GM parts was right at $120 and now I have peace of mind when my family is travelling. The blend door motor will take about 15 minutes at the most.Hope this helps.