This is my first post on this forum and I'd like to thank all those that share their information. This forum has really helped me to understand 4X4 operation.I have a 99 Blazer with a 4 button switch panel and front axle electric vacuum controller mounted on the firewall. When the ignition key turned on, the lights on the switch panel operate very intermittently, either on or off. When they do operate, the switch appears to operate normally. I checked the switch with an ohmeter and it checks out OK. I think the TCCM is defective. The next step is to check for any codes at Auto Zone. Can this condition also be caused by an intermittent motor assembly on the transfer case?Next purchase is a GM Blazer repair manual, the Haynes manual I purchased is of little help in this area.Thanks for all your help.

 

The Haynes manual is of little value in all areas You won't regret buying the GM shop manual, 3 manuals, over 3,000 pages covering your year Blazer only.

Check the electrical connector at the TCCM in the passenger kick panel. If water gets into the connector, the pins and sockets corrode. Clean them up and use silicon dielectric grease when you plug it back together.

 

Dude I have the same problem. Take out the 4 buttOn bezel and clean the electrical connections going to the buttons. That will more than likely fix it.

 

Thanks for your responses guys. I have cleaned and applied diaelectric grease to all the connections on the switch, TCCM and the transfer case. I still believe I have a bad TCCM and I will be able to tell more accurately when my GM shop manuals come in. Thanks again.