Trailer Brake Help

[RDrancher]

My flatbed is in the shop so I need to tow my GN with my old F350. All lights work but the trailer brakes will not activate either with the slider or pedal. GN connected to the flatbed truck and brakes work.

F350's Prodigy controller show no connection to the GN.
Brakes work fine when the F350 is connected to my other trailers.

Controller checks out fine, both for the slider and brake switch.
Using a 6-7 way adapter, but....
Voltage checks out fine at the 7 way trailer brake output terminal on the adapter when the brakes are applied.

Switched trailer brake and 12 volt constant connections on the trailer's plug to check brakes.
Plugging in with the 12 volt connection instantly activates the trailer brake magnets.
This would indicated that the trailer brake wire is working.
Switched the wires back to normal position and no brakes / controller shows not connected.

So...what am I missing?

 

[Diamondpilot]

My flatbed is in the shop so I need to tow my GN with my old F350. All lights work but the trailer brakes will not activate either with the slider or pedal. GN connected to the flatbed truck and brakes work. F350's Prodigy controller show no connection to the GN. Brakes work fine when the F350 is connected to my other trailers. Controller checks out fine, both for the slider and brake switch. Using a 6-7 way adapter, but.... Voltage checks out fine at the 7 way trailer brake output terminal on the adapter when the brakes are applied. Switched trailer brake and 12 volt constant connections on the trailer's plug to check brakes. Plugging in with the 12 volt connection instantly activates the trailer brake magnets. This would indicated that the trailer brake wire is working. Switched the wires back to normal position and no brakes / controller shows not connected. So...what am I missing?

On many 6 pin to 7 pin adapters they have two wires internally that can be switched. Check that.

If it were me though I would junk all the 6 pin stuff and replace the plug on the truck with a 7 pin. That's what everybody is using nowadays.

Chris

 

[RDrancher]

Chris, I took apart the adapter just to check and it's wired correctly. I actually have a 6 to 6 adapter that I use for rental dump trailers since you never know which way they're wired.

What I can't figure out is why I show voltage at the truck's brake output when the controller is activated AND why I can energize the trailer brakes with constant 12 volts from the plug. That means the truck is fine and the trailer's plug and brake wire are fine. I'm stumped.

 

[GPintheMitten]

Couldn't this be corrosion in the connector or similar mechanical connection in the connectors?

 

[KennyG]

Couldn't this be corrosion in the connector or similar mechanical connection in the connectors?

I think you're onto something. The connection the tester is making to both the truck and trailer side could be better than the connector pins are making. Also, when you get 12 volts with a tester (no load) it may not be the same as you get when applied to a load if there is resistance in the connector. Can you test a wire on the trailer downstream of the connector?

 

[joefromga]

In this case you can use a test light because the load is probably drawing more current than your multimeter does because of its low internal resistance.

Probably a ground problem or bad connector issue. You can even use a trailer bulb if you don't have a test light. Solder or wrap the center and the outside to 12v+ and ground. May light up may do nothing but probably barely lit.

How doesn't that trailer get ground? If through the hitch check corrosion on the GN mount and then the ground on the trailer itself.

 

[Diamondpilot]

Chris, I took apart the adapter just to check and it's wired correctly. I actually have a 6 to 6 adapter that I use for rental dump trailers since you never know which way they're wired. What I can't figure out is why I show voltage at the truck's brake output when the controller is activated AND why I can energize the trailer brakes with constant 12 volts from the plug. That means the truck is fine and the trailer's plug and brake wire are fine. I'm stumped.

Just because there is voltage that does not mean there is amperage.

I would look closely at the trucks ground a brake wire. Check with a test light, volt meter, and amp meter.

Chris

 

[mikesee]

Do the trailer brakes activate when you pull the break away pin? Not sure if that will help but it would be another bit of information.

 

[timswi]

We chased this down on my neighbors trailer by using a volt meter at the magnets and working towards the truck to find where the issue was..Often grounds are the problem, that's a fairly easy check. We found that the connectors at the magnets were lightly corroded and a ground was iffy.

His was like yours power everywhere but at the brakes...We ended up replacing the 7 pin connector and the breakaway battery for good measure.

 

[RDrancher]

Thanks for the advice guys. I'll start down the line on the trailer after work tomorrow and see what I come up with.