Bri-Mar Dump Trailer Battery Charging automatically ?

[Redbug]

I have an 06 GMC. It has the standard 7 pin hookup. I also have a dump trailer. The trailer battery will charge from the vehicle when the lights are turned on. That's the way GMC wired the truck from the factory. There is a blurb about it in your truck owner's manual. I'll bet yours is the same.

 

[Reg]

(Assuming electric trailer brakes).
Don't confuse breakaway battery charging with battery re-charging for the dump hydraulics/electrics.
Check this, but I'm reasonably sure that the breakaway battery is REQUIRED to be charged by the tow vehicle, the dump battery charging might well be optional.
I think the 7 wire plug has two +12V in it, one called +12V and the other called "AUX".
The AUX is probably the one to use for the dump battery re-charge.

 

[Diamondpilot]

You are right about that 12V and the Aux. I am a trailer dealer for boats and many of our trailers have hydraulic surge brakes. Some have electric brakes and some had the dreaded electric over hydraulic setup. With drums there is very little problem backing up but with disc brakes on the trailer that is another thing. We hook up what is called a cut out solenoids inline with the surge brake actuator and the trailer brakes. It receives its signal from the tow vehicles reverse lights via the Aux pin on the 7 way round trailer plug. I have seen some manufactures also hook it up to the running lights. Bad idea in this case because then you have no trailer brakes when the tow vehicles lights are on. I can not imagine what they are thinking.

Chris

 

[Redbug]

Good point Reg...I believe you are right on the two +12 volt pins in the 7 pin hookup. Now, you got me to wondering about my breakaway battery, (not the dump motor battery). I need to check it to make sure it is charging. I would assume the breakaway battery is charging full time? The AUX is the one for charging the dump battery on my truck. Good points...glad you brought it up.

 

[Diamondpilot]

It is not charging assuming the trailer is wired correctly to industry standards and you or someone else has not installed the fuse in your truck. This is a common problem I see with GM trucks in my trailer business.

Chris

 

[FritzII]

I should have added that it's a factory trailer package 7 pin setup and a factory harness on the Bri-mar.

The breakaway battery and dump battery are the same.

Turning on truck headlights does not make any difference.

40 amp and 30 amp fuses under hood are good and wiring is connected and correct.

Looks like I need to trace the wires on the factory Bri-mar pigtail ?

I picked up an online copy of the Bri-mar manual and it's looking like they do not factory wire it to charge the battery in the trailer. Looks like it's time to figure out their wiring.

 

[AlanB]

I should have added that it's a factory trailer package 7 pin setup and a factory harness on the Bri-mar.

The breakaway battery and dump battery are the same.

Turning on truck headlights does not make any difference.

40 amp and 30 amp fuses under hood are good and wiring is connected and correct.

Looks like I need to trace the wires on the factory Bri-mar pigtail ?

I picked up an online copy of the Bri-mar manual and it's looking like they do not factory wire it to charge the battery in the trailer. Looks like it's time to figure out their wiring.

I just looked at it I think it was page 138 and it showed it too me being there, but there is no substitute for running down the wires.

Should be a quick one with a test light, I don't think there is a diode or anything there, so you should just be able to read 12V on the trailer connector disconnected, then turn to your truck and you should have 12v on the matching truck side connector as well.

 

[FritzII]

This may not be too bad. It looks as if Bri-mar uses an 8 ft pigtail with 6 conductor cable and 6 pin male/female modular plugs. I'll bet I can tap their letter "D" which is what they have listed for +12 volt DC on the modular plug. Letter "D" is a black 12 awg wire.

I like the cutout idea so I don't blow the fuse under the hood. If I remember correctly the fuse is 30 amp and the unused aux. terminal is 40 amp. I think I have just the thing in my "Odd Stuff" drawer.

 

[FritzII]

I just looked at it I think it was page 138 and it showed it too me being there, but there is no substitute for running down the wires.

Should be a quick one with a test light, I don't think there is a diode or anything there, so you should just be able to read 12V on the trailer connector disconnected, then turn to your truck and you should have 12v on the matching truck side connector as well.

I don't know if the trailer battery is connected to the +12 volt terminal "D" on the modular plug, but I can find out real fast now using your method.

 

[Diamondpilot]

Fritz, stop for a minute.

Have you added the fuse to the under hood panel of your truck???? It does not come in from the factory, no matter what type of tow package you have. I have had to add them to many GM trucks through the years. I have not messed with a 08 but did one this winter to a 06 DMAX and a 07 DMAX and had to add the fuse to the panel on both of these trucks to make them charge the trailer. Both trucks had the tow package and the 7 pin harness but bottom line is GM leaves the fuse out and you need to buy one and put it in the right spot.

The best way to check this is to start the truck and go back to the 7 pin plug on your truck. Take a volt meter or test light and put the positive lead (red) on the pin at the 1 o'clock position as you look at it and the negative lead (black) on the pin at the 7 o'clock position. You should see 12+ volts here with the truck running. If not, you need the fuse. Trust me on this one, I sell trailers and work on these problems weekly. Not saying you don't have a problem with the trailer but start at the front, truck, and work to the back.

Chris