Trailer brake lights not working

[jcox07]

Got no brake lights working on the trailer but everything else works on tow vehicle to include the brake lights and everything works on the trailer except the brake lights. Check the ground at the tow vehicle and trying to find where the trailer would be ground at....any suggestions

[lcoleman]

There should be a ground pin in the plug. I think the whole circuit grounds back to the tow vehicle, not on the trailer itself.

[MARKP]

Checked the ground pin yesterday. It had less than .1 ohms resistance, measured on the trailer hitch.

The thing has me stumped. We can hotwire past the brake controller and get 12v to the correct pins by pushing the brake pedal. Verified 12v getting to the brake controller but not getting anything out when you step on the pedal. Manually operating the controller works fine. Tried two different controllers with the same result.

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[lcoleman]

Any problem in the actual plug going into the controlller? Bent/slipped pin or something?

[jcox07]

Just changed the plug on the trailer and now the turn signals and brake lights aren't working on the ambulance or the trailer so now it's worse.

[oldmuscle69]

Start by re checking the tow unit outputs,step by light. Then recheck the trailer connector. Next up is the connector for your trailer. pull it down and check every wire. Recheck the diagram from trailer to see what goes where as far as lights go.Double recheck the grounds.

[TedV]

everything works fine with the Excursion hooked to the trailer, but all goes fubar with the bambulance, right? don't let anything but the wiring touch when testing with the excursion. The ball hitch will substitute for a ground lots of times. Intermittent problems will be grease and corrosion on the ball and hitch