I have a ram 1500 that will not go into 4wd. I think it is a vacuum problem as my heater controll will not work as well. When I pull the 4wd shifter into 4 high or puch into 4 low it is changing but the 4x4 light dont come on ( i just replaced it so I know its good). In 4 low it changes to low gears but the front axel dont lock in. I just got the truck so trying to figure it out. And the heater temp dont shut off or change either. I removed the glove box and switched the controls around and the door didnt move that has the vacuum ram on it right behind the glove box. Any help would really help. Thank you

 

https://dodgeforum.com/forum/dodge-r...s-section.html

 

As for the 4WD issue, check the vacuum hoses at the CAD housing on the axle. If either of those are messed up, it will cause it to not function.

 

Since the heater controls don't work either, I suspect the problem is going to be up by the intake manifold, where the bag o' snakes vacuum lines are. Probably something disconnected/broken.

 

i have this same problem, but when i do put it in 4wd there is a kind of squeeking sound coming from the front end somewhere.....

 

ok it took awhile but found several vacuum leaks. now the 4wd works but my blend door motor for the ac dont along with the vacuum accuarto for the fresh air door. off to pick and pull i guess. anyone know what years will interchange for dash parts?

 

The blend door on a 2001 is operated with an electric motor. Make sure the motor works. If not, you most likely need one of these to fix it. http://www.heatertreater.net/index.html