Rth: very strange brake/ turn signal problem

[40TUDE]

Let me start by sayin that I am relaying this info. My father and brother are driving cross country in 99 hundy. The right turn signal works normally, when the left turn signal is turned on, the brake lights engage and there is a pulsing felt as if the brakes themselves are trying to engage. No idea what would cause this. I will say that I know the sunroof did leak at some point. Any help appreciated.
Thanks

 

[geocruiser]

Let me start by sayin that I am relaying this info. My father and brother are driving cross country in 99 hundy. The right turn signal works normally, when the left turn signal is turned on, the brake lights engage and there is a pulsing felt as if the brakes themselves are trying to engage. No idea what would cause this. I will say that I know the sunroof did leak at some point. Any help appreciated.
Thanks

Could possibly be faulty wiring in the trailer lights/control wiring (if the truck is so equiped), especially if the wires were spliced into the truck's wiring during installation.

I would have them look in the rear quarterpanel area, behind the taillights, or under the truck to see if they could find any wiring that looks bad.