Wiring a dolly with electric brakes

noiva · 02-14-2006, 12:56 PM

I've recently seen an ad for a Master Tow dolly with regular electric brakes like a trailer, not the typical surge brakes they usually come with. My question is: since the tag axle on my 370 already is an electric trailer brake, and has a brake controller (without a manual override), would there be any unusual things to know if I wanted to hook up the dolly with the electric brakes? I'm thinking particularly about such things as, would I need a 2nd controller for the dolly since the tag controller doesn't have any way to over-ride the tag brake force? Assuming the need for 2 controllers, would there be any conflict between the two? How could they be electrically separated, or would they need to be? Anyone ever done this before? How did you do it?

Thanks,

lewster · 02-14-2006, 04:46 PM

Tim,

I've never seen it done but it should work (in theory, of course). I would use a separate controller for the dolly so it would be treated just like towing a normal trailer. This would allow you to set the gain on the controller properly for the load of the dolly and car and would not interfere with the settings or operation of the tag axle and the braking of the MoHo.

I don't see any issues with wiring as long as you do a completely new install with the new controller and use it's own 7 way plug, etc.

noiva · 02-14-2006, 05:42 PM

Quote:

Originally Posted by lewster

Tim,

I've never seen it done but it should work (in theory, of course). I would use a separate controller for the dolly so it would be treated just like towing a normal trailer. This would allow you to set the gain on the controller properly for the load of the dolly and car and would not interfere with the settings or operation of the tag axle and the braking of the MoHo.

I don't see any issues with wiring as long as you do a completely new install with the new controller and use it's own 7 way plug, etc.

Lew,

Thanks. Do you see any issues with splicing into the wiring at the same places the tag controller is wired, or should I at least run the wire that actuates the brakes separately to the rear of the coach (and then into the 7 way plug)? I'm thinking if I don't I could get braking activated on the tag from the new controller. Does that sound correct?

lewster · 02-14-2006, 06:12 PM

Tim,

Try to isolate the new wiring as much as possible to avoid any 'feedback' issues. Using the same splice points might give you feedback. You might need diode 'isolators' to prevent the current from going from one controller to the other if this condition happens. I've seen it on flasher circuits that pulse the controller. This would be on the brake light circuits only, as the power, running light and turn signals would be the same. By that I mean making the connection for the controller to the cold side of the brake pedal wire itself, not to the one running to the other controller.

OTOH, as long as the controllers are each set for their individual purposes, there might not be a problem in sharing the wiring as they will each be activated at the same time anyway. I would definitely separate the power, ground and brake wire (blue) leads though from each controller.

noiva · 02-14-2006, 06:47 PM

OK, one other question. Everyone who's written me about towing with a dolly has said they were very satisfied with surge brakes. Some don't even use any brakes, but that is now illegal in most states, and I really don't want the added load without brakes anyway. Since the surge brake dollies are less expensive, and there could be some issues with running 2 controllers, perhaps I should just stick with looking for one with surge brakes. Any opinions/experiences with that?