Weird aux light issue!

[suprz]

This is on a 2006 Ford E450 chassis. I have a motorcycle carrier that I had some cheap magnetic towing lights on, on our last trip, I noticed that all the lights worked ( turn, brake,hazards, except the running lights... I figured that it was the 7 to 4 pin connector because I had the same problem while using my jeep towing a UHaul trailer. So now, I got some new LED lights, wired them up, AND got a new 7 to 4 pin connector, and I have the same issue! Now here's where it gets really weird... I checked the adaptor with a voltmeter and all the pins are fine! I checked the adaptor by itself plugged into the motorhome with the voltmeter and again all pins get power except the running lights... So I check the new adaptor on my jeeps 7 pin socket and get the same results! Everything but the running lights! So, I know the adaptor is good, I know the carrier light wiring is good too... So am I supposed to believe that two separate vehicles have exactly the same issue? I checked the 7 pin on the motorhome, and get no power to any of the pins when the running lights are on. Thoughts?? (all the lights function fine on the motorhome)

[enblethen]

This may help. Look at F1-24
fuse block

[wa8yxm]

This was on a car, not being towed, and not an RV but I got stopped for no tail lights.. Sure enough they were not working.

I traced teh fault to a connector It was in a place where wheels tossed water up and it was SUPPOSED to hit a plastic panel but the panel was cracked so it sprayed all over the connector.. Result.. I bypassed every pin on that plug with soldered jumper wires and sealed them.

Later I had a problem with my Freezer. it runs on 12 volts normally (120 volts when I have to) Well it was not being fed.. Voltmeter showed 11.something when no load droppign to zilck undewr load.. Problem was in a wire.. Thankfully there is but one wire between the battery and the test point.

I sliced out the bad part. soldered in a jumper and sealed it.

[enblethen]

Many Fords have fuses for the trailer connector. Check your owner's manual if you have one.

[suprz]

I got under the motorhome and followed the wires for the 7 pin, and it comes out from behind the drivers side rear tail lights. So it looks like I will have to pull the entire tail light assembly to check how the wires are attached and see if the brown wire is not connected etc...

[RoyB]

Google image

Most often these are ground issues when they get to doing wierd things...

ETRAILER is a good place to goto to look at wiring diagrams etc...

Roy Ken

[MEXICOWANDERER]

"I checked the 7 pin on the motorhome, and get no power to any of the pins when the running lights are on"

I cannot think of a better place to start fixing things than right there

[Sam_Spade]

YOu need to check the grounds in the connectors.

IIRC, there are TWO pins that are supposed to be ground.
BOTH are supposed to be used for increased reliability; a cheap and dirty installation might use only one. If the next guy cutting corners decided to use the OTHER one.....you have a bad ground.

And yes, some of the lights will work without a good ground, sometimes.