what would cause an elect./ vacum 4/w/d on a 93 jimmy not to work?

Question

1993JIMMY 4w/d won't work, it has a shitch on the dash that shows a yellow light when i try to switch to 4w/d H.. thanks

Answer 1

First check the fuse, next check the vacuum hose going to the switch and last check all the electrical wiring as being secure.
If everything seems OK, take it to a qualified tech for diagnosis.
Master tech 40 yrs.

Answer 2

It's a vacuum problem. Your vacuum supply runs from the differential to the transfercase, and then runs to the intake manifold. You could possibly have a vacuum switch at the differential causing your problem too!
I'd recommend jacking the front end up and putting in 4WD and checking vacuum at the differential, if no vacuum found, go to transfer case. You'll have a vent tube and a vacuum tube, check for vacuum there. If no vacuum found, trace up to the intake manifold and you should find your problem.
Now if you check the defferential and you do have vacuum, replace the vacuum switch.
Hope this helps!

Answer 3

Good advice above. Vacuum leaks are the main reason. There can be other problems, but check the basics.