Blinkers Do Not Work with Running Lights On on a 2007 Freightliner XL Classic  

Question:

Expert Reply:

You will first need to make sure that the new tail lights are wired the same as the old ones. There are basically 2 types of wiring systems. First there is a 2-wire system that has combined turn signals and brake lights on the same circuit/bulb. And there is a 3-wire system that has separate circuits/wires and bulbs for turn signals and brake lights. On many tail lights the functions of the wires is listed on the back of the assembly. Since there isn't a standard wire color/function code you would have to wire in the lights by function, not color.

If you are using the right type of tail light assembly then the issue could be a bad ground. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light. Make sure that the ground wires or studs are attached to clean and corrosion free bare metal surfaces.

expert reply by: Michael H

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