flashing lights

i have a 2003 chevy venture and when it rains or after it rains and sometimes for no reason my head lights flash on and off for 30 mins or more at a time i have tried replacing the bulbs but did not seem to help. please any susgestions at all!!!!

Ok, never heard this one.
There is a known problem where the taillights get water in the harness connector. You need to clean and inspect both rear lamps for this conndition. When the wires do get wet in the connector, what you generally see is the left & right turn indicators come on when you step on the brakes. Also the signal will flash very fast when the brakes are used. The short effects other things in the van as well, once I had the radio display flash on and off with the turn signal indicators. Cleaning and drying the connectors in the tail lights solved these problems.

The lift gate in the rear of the van leaks in the rain as well. At the point on the roof where the two wire bundles enter the lift gate, there is a water seal that goes bad and allows water to enter the cabin and pool on the floor just inside the lift gate. It can also short those wires out.

I know it seems silly to suspect the taillights when the headlights are acting up, but check your wiring back there.

John