On my 06 3500 I have the factory 7 pin trailer plug and the 4 pin plug. The lights on my 5th wheel trailer work fine connected to the 7 pin plug. However when I connect my quad trailer up to the 4 pin connector all the lights work except the right brake light and rt turn signal. I have checked all the fuses I could find and checked the wiring, all seem ok. The voltage reading at both plugs is 12 volts when brake pedal pushed. Thanks in advance for any ideas.