I am sure this has been asked and answered already but I am new and don't know how to find. My hummer only seems to switch between the drive modes when it is cold out. 4 high- 4 high locked etc. i have replaced switch and actuator motor to no avail. Am i missing something? When i start it sometimes indicator light doesn't come on and i switch to 4 high locked and back then it comes on with a clunk from underneath. I only have 70k miles. A lot of times i don't here the clunk even though the light indicates 4 high unlocked and i feel the tires jump so i know it hasn't been disengaged. The actuator was an auto zone reman the new switch came as NOS. so everything works great when it is cold out, stops working correctly when everything starts to warm up. Maybe wiring? Where would i look? Also, "service 4wd" does not come on in any situation.

 

MOVED from the Drivetrain Area where it says: "This section is an archive of older posts, please post new questions in the specific model section. Thank you! "

 

I'd had similar trouble on my '08. I swapped the actuator with reman too. Still did not work as expected. I returned it and got another reman from same parts place and have had no trouble since. Maybe they sold you the one I returned!
I did have a buddy with Snap-On scanner check out the H2 before returning it. The scanner confirmed the operation was not right. Of course the orginal was having poblems too. He checked it out for free... If that wasn't free I would have still returned it and swapped. His scanner it some really good high dollar one not cheap one that only reads engine light codes.

 

Thank you! Really was what I was thinking!