4 wheel drive problems

2000 Envoy, when trying to put into 4-hi or Auto 4. Lights on switch just blink. Sometimes they stop and the 4WD seems to work, but when you start to speed up the lights start blinking again, indicating it is not engaged. I have already changed the Auto transfer case control module because it was bad. Now I am thinking it is the electronic shift motor in the transfercase. Also whats up with these EXPENSIVE Xenon headlights, can I go back to the standard lights?

try the front axle switch, then the encoder motor , all parts can be found online for atleast 1/2 of cost from the dealer.

Yes you can go back to standards. Just check out your friendly local car parts store and use their computers to search for a matching standard bulb.

I found the problem by putting the vehicle up on four jack stands. I tried to get the fwd engaged and it would start to rotate the front tires. But when i accelerated they stopped rotating. I changed the electric shift motor and while the old one was cracked and letting corrosion inside it did not help. What I found was a vacuum line from the fire wall to the vacuum ball below the battery that engages the front axle had a burn hole in it. There was not enough vacuum when I accelerated to keep the axle engaged. Replaced the line and problem solved. Goes to show that even with all the computers and electronics, sometimes it is still the simple things.