No Tail or Running Lights - What Should the Voltage Be on a 7-Way Connector For Running Lights

Updated 04/08/2020 | Published 01/28/2010

Question:

Hello, we have a trailer with a 7 way connector. the brake and blinkers work but we have no running lights. Any ideas? what voltage should I read on the running light pin? There are two small lights and one three light bar on the rear with two wires for connection, one being a ground.

asked by: James

Expert Reply:

You should be seeing around 12 to 14V on the running light pin with the headlights turned on. If you have not already done so, check the grounds on the side markers and running lights make sure they are connected and not frayed. Check the running light circuit wire along the trailer and check for nicks for frays or loose connections.

Depending on the vehicle, you may have a blown fuse somewhere on one of the vehicle fuse blocks that provides power to the tail light circuit.

expert reply by: Patrick B

Eric A.

4/7/2020

I was installing a RV backup camera and the power supply taps off the upper running light. I had an issue with the camera and when I checked the DC volts it was 8.6 VDC coming off the running light, the lights worked fine, leaves me wondering if its a camera or voltage issue DO you have any ideas?Thank you

Chris R.

4/8/2020

It could definitely be a voltage issue on that circuit. You could test this by simply connecting the camera wiring directly to a 12V source like the battery. If it works then you know the running lights circuit is the problem. If this is the case there are a couple of things you can look at to increase that voltage. If you're using a smaller gauge wire for the circuit, you can replace it with heavier gauge wiring to decrease resistance. Also make sure the harness and light assembly grounds are securely attached to a bare metal surface, as a weak ground can lead to lower voltage too.

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