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Old 04-09-2016, 12:21 PM   #21
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Have you tested the plug on the truck, to make sure you have running lights there?
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Old 04-09-2016, 12:22 PM   #22
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My GMC had a factory installed towing package but the dealer never hooked up the charging wires during dealer prep.

I had to do this myself.
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Old 04-09-2016, 12:30 PM   #23
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Ya, I tested the 7 pin on the truck and everything shows power, seems odd to me that all the marker lights and the rear running lights would be faulty at the same time - suggests to me that it's not just the bulbs. Would there be a separate circuit for just running lights?
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Old 04-09-2016, 05:29 PM   #24
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Many pickups have separate fuses for the trailer light wiring that go back to the 7 pin connector. Might check the fuse panel in the tow vehicle.
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Old 04-09-2016, 05:35 PM   #25
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If you are getting voltage for everything at the 7-pin connector the next step is to connect the trailer and check the voltages where the 7-pin cable connects to the trailer wiring. This will tell you whether it is in the 7-pin connector/cable or the trailer wiring.
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Old 04-09-2016, 05:40 PM   #26
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Originally Posted by Davinderr View Post
Thanks to everyone for the hints and tricks. I have checked the truck fuses and 7 pin connection truck side, and cleaned all the plug contacts and am getting brake and signal lights, but still no running lights when plugged into the running truck with the lights on. Am I still missing anything? I should mention that I do not have the trailer battery hooked up at this time as the trailer is still in storage. Could this be the source of my trouble? Sorry if these seem like newb questions, we are fairly new to RV ing. As always, any thoughts are appreciated.
Neither the house batteries nor the break away battery have anything to do with the running lights. The running lights operate off the TV battery. One of these posts gave the 7-pin config. locate the circuit pin for the running lights at the TV plug and test for power at the TV outlet. Use a volt meter or test light. If the TV outlet has power, it has to be the TT. You may be looking at corroded terminals behind the 7-pin connector on the TT. If your plug has been hanging with the pins toward the ground, moisture can get into the plug causing corrosion. It pays to put the TT plug in a plastic bag for long storage and tape it closed to seal the moisture out,

If you have brake lights and turn signals on the TT, it is not a common ground problem. It could be a ground specific to the running lights.On an aluminum skinned TT, the running lights may be grounded to the skin. With fiberglass, there has to be a hot wire and a common wire to each running light. If you have power behind the TT 7-pin connector, ground could be the culprit.

Be it the hot or ground, the first thing I would be looking for is a corroded terminal. I have seen corrosion inside crimped terminals, so look closely.

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power, tow vehicle

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