Ok so what your saying is that with the tail lights on and the brakes on
the the left side (drivers) does not work but with the lights off the brake
lights work fine or visa verse .....//you have a high resistance in the
ground on the drivers side ....//it can handle the park light (its most
likely dimmer on that side) but when the brake is added it is to much
current for the circuit to handle ...check the circuit with an Volt /ohm
meter ...it could be a socket or if you have trailer wiring harness it
could be were the spliced it in ....// the ohm meter will help ...//most
likely its corrosion so you may have more than one wire that is open
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