I've encountered a similar issue before with my last van. exactly what Greg suggests below is what  I found. I had installed the trailer harness incorrectly. Re-checked my trailer connections until I found the problem. My lesson learned: don't trust the color coding of the wires. Check them with a volt/ohm/continuity meter.

Gregg
90 Westy

Sent from my mobile device

On Mar 27, 2011, at 7:37 PM, Greg Potts <greg@POTTSFAMILY.CA> wrote:

> Hi Jonce,
> 
> Sounds to me like the brake light circuit has been crossed into the
> parking light circuit, which connects in turn to the dash lights.