Troubleshooting Pop Up Camper Trailer Left Signal/Brake Light Not Working  

Question:

Expert Reply:

The first place I always check is with the bulbs. The 1157 Incandescent Bulbs # DI79VR are easily damaged internally and not always visible. If you do not have a known good spare you can simply swap it with the passenger side bulb since you know that works properly. This will allow you to eliminate the chance of the bulb being bad.

If the bulb is know to work then I recommend checking with any fuses that you may have on your vehicle. If your tow vehicle came from the factory with the trailer wiring it will have fuses that regulate the power to the trailer. You can check your owners manual for their placement.

Next I recommend using a Test Light # PTW2992 to ensure that you do have positive power going to the connector when the left turn signal/brake lights are activated. On the vehicle connector this will be the center of the 3 female connectors. If you do not have power the issue is on the vehicle side of your harness.

If you are getting power to all circuits of the vehicle connector you will want to verify the ground wire on the left taillight is good. With the age of your 1970 Starcraft Starmaster 8 the ground wire from the taillight may go to the trailers frame or run all the way back to the trailer connector. You will want to ensure that the wire is not damaged, the Test Light # PTW2992 can also check for a good ground connection or you can use a Multimeter # PT89ZR to check the continuity between the negative of the side of the taillight assembly and the trailer side connector.

I have added an article below that covers the trailer lights on a basic 4-way wiring that you can reference for additional information.

expert reply by: Bud M

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