7-Pin No Running Lights

dougrainer wrote:
IF you have truck running lights and just NO trailer running lights, you have the Trailer light fuse blown on your truck. Trucks and motorhomes built in the last 15 years, have a separate fuse for the truck lights and the tow plug lights. This prevents a tow vehicle short from taking out all the running lights. You even have a separate fuse for the Left and Right Turn signals on the tow plug. The usual location of the tow plug fuses is under the truck hood, not under the dash. Doug

Thanks, that is my next step tomorrow. I came home through south Texas with my emergency flashers on. As I said, all other lights worked so it wasn't an issue.

I will update tomorrow. Good info here.

RoyB wrote:
You need to determine if it is a problem with the trailer or truck. This is where my 7-way test adapter listed earlier comes in handy

You can also test your running lights on the trailer by just using a short wire between blades 3 & 4 on the trailer cable PLUG end. Your trailer battery has to be functional to do this.



Roy Ken

Thanks for the advice. I did what you said this morning and there are trailer lights. Next step, truck fuse.

IF you have truck running lights and just NO trailer running lights, you have the Trailer light fuse blown on your truck. Trucks and motorhomes built in the last 15 years, have a separate fuse for the truck lights and the tow plug lights. This prevents a tow vehicle short from taking out all the running lights. You even have a separate fuse for the Left and Right Turn signals on the tow plug. The usual location of the tow plug fuses is under the truck hood, not under the dash. Doug

You need to determine if it is a problem with the trailer or truck. This is where my 7-way test adapter listed earlier comes in handy

You can also test your running lights on the trailer by just using a short wire between blades 3 & 4 on the trailer cable PLUG end. Your trailer battery has to be functional to do this.



Roy Ken

katysdad wrote:
Check the fuse block under the hood, some vehicles have seperate fuses for trailer lights

Will do first thing in the morning. Thanks.

Check the fuse block under the hood, some vehicles have seperate fuses for trailer lights

No blown fuses that I can see. Hmm . . . What next? I followed the wires and no issues there. I had that problem with another tow vehicle but all lights were out.

I had no running lights. No one could figure it out.

One day I was under the RV looking at something else and saw where they ran the running light wires from one side to the other up and along the frame. The wires had come apart where they spliced it. It was hidden because they had used zip ties so it was not hanging down where it had come apart. :R

I carry one of these 7-way trailer lights testers (ETRAILER - AMAZON)...

If all of the LEDs on this tester works properly when plugged into the truck connector then your problems is on the trailer side...

Sure helps when looking for where the problem is...



Roy Ken

qtla9111 wrote:
Just hooked up and ready to pull out tomorrow morning. All lights; brake, signal, emergency, and brake controller work fine. No running lights. I have the diagram for the 7-pin connector. I have cleaned and tighted/untightened the connector for running lights to no avail.

Any suggestions? Thanks in advance.

https://www.etrailer.com/question-28070.html





This shows the picture of the terminals. If you don't have power to the wire for running lights, then the fuse in the tow vehicle might have blown.

On my motorhome, I proptly blew the fuse for my motorhome running lights when plugging in my brothers cargo trailer. What I did was measure the voltage at the rear terminal (after re-setting the fuse) and then found it was only 9 volts. I hooked up a 12 volt relay to a 20 amp power circuit from the battery (same that my water pump runs from) and then power that relay from the 9 volts (what is left after all the running lights cause a voltage drop across the line from the light switch to the back bumper).

Then the relay transfers a full 12 volts to the trailer on a separate circuit breaker. So my guess is my motorhome running lights are using 10 - 15 amps, and the trailer is using almost the same amperage, tripping the 20 amp circuit breaker. After installing the relay, now the trailer lights came from the 20 amp circuit, so I did not trip the CB again.

Fred.