Mfi trailer brakes

[aarons1k]

I was reading some other posts about mfi surge brakes and backing the trailer up... I always thought u could only back trailer up with the key in the tounge ? Some said depending on how your trailer harness was wired it could over ride it , with out keg ???

 

[itsdgm]

The fifth wire (blue) on the trailer wiring harness is for trailer brake lockout. This wire should be connected to the vehicles reverse lights. So when the tow vehicle is put in reverse a solenoid opens up a valve on the trailer actuator and releases the pressure in the brake lines. This enables the trailer to be backed up without activating the surge brakes.

Edit: the above would be for normal operation. The reverse lockout key is if the above system fails. Hope that makes sense.

 

[aarons1k]

The fifth wire (blue) on the trailer wiring harness is for trailer brake lockout. This wire should be connected to the vehicles reverse lights. So when the tow vehicle is put in reverse a solenoid opens up a valve on the trailer actuator and releases the pressure in the brake lines. This enables the trailer to be backed up without activating the surge brakes.

Ok I am going to have to look for the blue wire , cause I can't back up w the key out ...

 

[itsdgm]

The blue wire would be on the trailer side. Not sure what color to look for on the Chevy. But here's a diagram of a 7 way round connector found on most vehicles. So you would want to see power on the reverse light connection when the vehicle is placed in reverse.

 

[Boat Crazy]

Your truck may only have a 4 wire plug. If that is the case you can buy an adapter that has 4 plugs and one additional wire coming out of it to wire into your reverse lights. Than the other end has a 5 wire plug That plugs to trailer. If your truck has a 7 wire plug you can buy a 7 - 5 wire adapter. All these can be purchased at a local automotive store.

 

[aarons1k]

I usually always unplug my trailer before I back it in the water ..... Is that why they give you the key too?

 

[aarons1k]

Your truck may only have a 4 wire plug. If that is the case you can buy an adapter that has 4 plugs and one additional wire coming out of it to wire into your reverse lights. Than the other end has a 5 wire plug That plugs to trailer. If your truck has a 7 wire plug you can buy a 7 - 5 wire adapter. All these can be purchased at a local automotive store.

Okay my Trk has a 7 pin , and the boat has a flat 4 pin connector , so I have to cut the 4 off and install a five ?

 

[Boat Crazy]

No, when you back in the water your trailer should back up with no brake resistance because you are backing down a ramp. You should not need your brakes pinned even if you have 4 wires To back down the ramp Because your brakes are not surging forward.

 

[Boat Crazy]

Okay my Trk has a 7 pin , and the boat has a flat 4 pin connector , so I have to cut the 4 off and install a five ?

Nooooo ! do not cut any wires. Go to your local walmart or auto store and buy a 7 -5 pin adapter. Plug the adapter into your truck and the trailer into the other end. WALAAA! you can now back up without the brakes pinned.

 

[Boat Crazy]

@Aaron Stammet Are you saying the trailer only has a 4 wire plug? I am thinking it should be a five wire plug On the trailer. 4 male, 1 female.

 

[aarons1k]

Are you saying the trailer only has a 4 wire plug? I am thinking it should be a five wire plug On the trailer. 4 male, 1 female.

I just went to check , they guy zip tied a 7-4 onto the trailer 5 pin lol I just ordered a 7-5 . Thanks for the clarification and help ! Now I will be able to back it up w out messing w that key every time lmao!

 

[aarons1k]

No, when you back in the water your trailer should back up with no brake resistance because you are backing down a ramp. You should not need your brakes pinned even if you have 4 wires To back down the ramp Because your brakes are not surging forward.

Ok ! Perfect ! I haven't had it in the water because this xrappy IL weather !!

 

[Boat Crazy]

I just went to check , they guy zip tied a 7-4 onto the trailer 5 pin lol I just ordered a 7-5 . Thanks for the clarification and help ! Now I will be able to back it up w out messing w that key every time lmao!View attachment 20838

When you say ordered? You can purchase the 7- 5 adapter at any auto or walmart store. Cut the zip tie and, pull the 5 plug off, plug to your 7-5 adapter and all should be good.

 

[aarons1k]

When you say ordered? You can purchase the 7- 5 adapter at any auto or walmart store. Cut the zip tie and, pull the 5 plug off, plug to your 7-5 adapter and all should be good.

Yeah I ordered it since i am leaving from Florida Sunday am the boat is staying home but I'll take the sun and sand !

 

[Boat Crazy]

The brake pin you are using to back up is designed for emergencies. Wired correctly, you should not need it for normal operation. That said, make sure you have it for emergencies.

 

[aarons1k]

The brake pin you are using to back up is designed for emergencies. Wired correctly, you should not need it for normal operation. That said, make sure you have it for emergencies.

Ok , makes more sense now , my other trailer didn't have brakes so this is all new

 

[Boat Crazy]

Glad you can put this all behind you. Now, go enjoy Florida.

 

[aarons1k]

Glad you can put this all behind you. Now, go enjoy Florida.

Thanks !!!!

 

[sysinu]

Remember that your surge must not be active when you put the truck into reverse. The back-up light from your 7-pin adapter connects to the 5th pin and that effectively activates a solenoid that does a bypass of the hydraulic fluid... So in short, if your surge brakes are already on and you put her into reverse, the brakes are still going to be locked.

P.S. I hate surge brakes.

 

[txav8r]

The brake lockout key is also used when you use a vehicle that doesn't have light hookups, like a tractor or other yard vehicle. But like @Boat Crazy says, it isn't for normal use...unless your brakes are messed up and you have to bleed them to disable and then use the key to prevent inadvertent application...ask me how I know about this. lol