2000 Venture dashboard lights

My 2000 Venture has 111,500 miles and has been pretty much trouble free. Recently when I turn on the headlights ( or they come on automatically with the sensor ) the dashboard lights all go out. They turn on for a milli-second, then go dark. I searched and searched, and then took it to a dealership where it had some other maintenance done to it.Their guy told me that it was probably due to the remote starter or the 10 disc CD player that I installed. I double, and triple checked my wiring, and found no pinched or chaffed wires. He then said that it seemed to be coming from the grey wire out of the switch to the different circuits. I again traced this as much as I could do and found nothing. I bought the Haynes manual, and followed their proceedure to test the switch itself, and it tested OK. Does anyone have any ideas, because I'm at loss for what to check next! Thanks in advance for any advice!

You're right, this can not be a failing switch. I wish I knew what it was, on my 98 Venture it happened suddenly while I was driving.
In normal situation whenever the headlights are turned on the radio and overhead dims down a bit. Only now on mine they dim down for a split second and then turn completely off just like megapea was saying. I'm wondering if there is some kind of relay that has gone bad.

I was suggested to just try to replace the headlight switch. I purchased the part to replace the dimmer/headlight switch, unfortunately the brand new part does the same thing. As soon as the ligths are turned on the radio/clock, dash and overhead console ligts all go out.

I tried disabling the DRL (Daytime Running Lights) - no luck.

What I did notice though was that if the car is not running (no key in ignition) and I turned on the headlights and hit the "recall" button on the radio - the cadio/clock backlight works - usign the dimmer wheel I can even adjust the lighting for the radio/clock. So as I think of it - this means there's nothing wrong with the switch. However as soon as I turn the ignition key to any other position than "off" the dash lights go out when the headlights are turned on.

PLEASE - if anyone has any ideas of what this could be or has resolved this problem - please, please let us know.

On the above problem try looking at the DRL module these go out all of the time and can cause eratic dash headlamp problems.

Also if you are not blowing fuses and light are going dim then cutting off in the tail gate section look at the rr wiper motor assy and the lic plate lamp wire they frey and short out was a bear to find more in ple e-mail me I am going threw this now with multi problems.