Trailer running lights fuse blows if exhaust brake is used

[BnR]

Hi,
New member looking for information....I have a 2006 Damon Astoria that the previous owner had setup to tow his pickup. I have a boat to pull and what I found is that if the exhaust brake on the MH is on and used, the 20amp fuse for the trailer running lights will blow. If I leave the exhaust brake switched off the trailer lights all work as expected.

Since I'm new to DP motorhomes and how people setup of TOAD's....is there something with the exhaust brake setup that would cause this fuse to blow when my trailer is plugged in? I would like to fix this soon as we are heading to Lake Shasta soon and will be pulling the boat over the passes and I would like the exhaust brake option to work.

Will also add the when I bought the MH the previous owner said something about if towing a trailer and the exhaust brake is on the trailer brakes will lock up when the exhaust brake kicks in....this did not happen on my boat trailer. The boat trailer brakes do not lock up when the exhaust brake kicks in.

Thanks for any insight in this-

Bob

[MSHappyCampers]

Hi Bob! Welcome to IRV2! We're sure glad you joined the gang!

Sorry, never heard of that one! Have fun and keep her between the ditches!

Good luck, happy trails, and God bless!

[Gary RVRoamer]

On many coaches the exhaust brake triggers the coach brake lights to come on. If the trailer brakes are also activated by the brake light switch, it too brakes. Some owners hate that, while others like it. The main worry is that the trailer brakes may heat up on a long gentle downhill. The type of brake controller plays a role - those that are not inertial will gradually increase braking (more amps) the longer the brake is active. Inertial controllers won't do that based on time alone - they modulate for the amount of braking actually being applied on the coach.



I don't know what may be unique about your Astoria but obviously the exhaust brake is causing more amps thru the light circuit. You need to identify exactly what that 20A fuse actually serves and then see what happens when the brake comes on.

[FIRE UP]

Originally Posted by BnR

Hi,
New member looking for information....I have a 2006 Damon Astoria that the previous owner had setup to tow his pickup. I have a boat to pull and what I found is that if the exhaust brake on the MH is on and used, the 20amp fuse for the trailer running lights will blow. If I leave the exhaust brake switched off the trailer lights all work as expected.

Since I'm new to DP motorhomes and how people setup of TOAD's....is there something with the exhaust brake setup that would cause this fuse to blow when my trailer is plugged in? I would like to fix this soon as we are heading to Lake Shasta soon and will be pulling the boat over the passes and I would like the exhaust brake option to work.

Will also add the when I bought the MH the previous owner said something about if towing a trailer and the exhaust brake is on the trailer brakes will lock up when the exhaust brake kicks in....this did not happen on my boat trailer. The boat trailer brakes do not lock up when the exhaust brake kicks in.

Thanks for any insight in this-

Bob

Bob,
Well Sir, first off, other than the exhaust brake activating the brake lights on the coach, it has absolutely NOTHING to do with any other operation, especially lighting. It is a mechanical operation that, closes off the exhaust, to create back pressure in the coach engine exhaust system which, slows you down due to the back pressure. And, due to the fact that you're slowing down when the exhaust brake is in use, it also activates your brake lights, on the coach.

But, guess what, so does your brake pedal activate the brake lights. So, in theory, if the activation of the brake lights by the exhaust brake caused a fuse to blow, so should the activation of the brake lights by applying the brake pedal.

Now, I've been a boat person for decades and, about 99.99999999999% of the boat trailers I've EVER seen and towed, had SURGE brakes on them. There was absolutely ZERO electrical involved since the tongue of the boat trailer has a mechanical surge hydraulic brake master cylinder on it. Now, that's the norm.

But, there is also a high end boat trailer, normally at least a three axle one, that utilizes an electronically operated, hydraulic application, set of disc brakes on the boat trailer axles. Just how many of those are in operation, not a clue. But, if yours is one of those, and, you tow it with a D/P that has an exhaust brake, well Sir, yep, you're gonna get operational trailer brakes due to the exhaust brake activating the coach brake lights which, will send a signal to the electro/mechanical/hydraulic brake master cylinder on the boat trailer.

But, even in that case, there is absolutely ZERO reason for any fuse(s) blowing when the braking is in operation. Brake lights and running lights are totally separate. I myself, am suspecting that something else is a problem here. You don't say what kind of braking system you have on your boat trailer. If you have a standard surge brake master cylinder, you may be getting a short of some sort as your coach is applying the exhaust brake due to the wiring maybe close the operation of that master cylinder, just a guess here.

Without seeing your operation and checking out all the wiring, including the wiring at the trailer plug on the coach, the plug that comes from the boat trailer that plugs into that coach plug, and a few other things, this is hard to analyze and come up with an accurate answer. keep us informed. I'd like to know what's the issue here.
Scott

[l1v3fr33ord1]

Bob-

What make and model of trailer brake controller is installed in your coach?

[BnR]

Thanks for the replies everyone. I need to dig into the coach and see if I can find what brand/model of tow controller the previous owner had installed. I agree, the boat trailer has surge brakes and the exhaust brake should do nothing but turn on the brake lights.

I also posted this question on a Malibu boat forum I'm on too and the consensus there seems to point at a possible short in the trailer. But I'm not sure on that since the trailer lights seem to work fine if hooked up to my truck or the motorhome if the exhaust brake is not enabled/used.

Will post more info when I get details....

Bob

[FIRE UP]

Originally Posted by BnR

Thanks for the replies everyone. I need to dig into the coach and see if I can find what brand/model of tow controller the previous owner had installed. I agree, the boat trailer has surge brakes and the exhaust brake should do nothing but turn on the brake lights.

I also posted this question on a Malibu boat forum I'm on too and the consensus there seems to point at a possible short in the trailer. But I'm not sure on that since the trailer lights seem to work fine if hooked up to my truck or the motorhome if the exhaust brake is not enabled/used.

Will post more info when I get details....

Bob

Hey Bob,
Thanks for getting back here. Now, here's the deal. Whether or not, you use the exhaust brake or, apply the brakes in the coach, or apply the brakes in THE TRUCK if you're towing the boat with the truck, any one of those, exhaust brake, applying brakes in the coach, or applying brakes in the truck, will cause a "surge" of your trailer to push against the brake master cylinder on the trailer tongue. And, if there's a short in the trailer wiring, near that master cylinder, that's causing you to blow fuses IF and when, the trailer surges, then that fuse should blow ANY TIME, any of those above conditions are in place.

If you are towing your boat with the coach, and apply the brakes enough for a good surge, and you don't blow any fuse, then something's' amiss here. Again, because all the exhaust brake does is slow the coach which, causes the trailer to surge forward which, causes the trailer brake master cylinder to activate the brakes on the trailer, simple. But, if it's ONLY the exhaust brake that causes the blown fuse, this is a Rod Serling Twilight zone issue for sure.
Scott

[BnR]

Just thinking...is there anyway to engage the exhaust brake easily without actually starting the motor up and moving? Would like to test voltage at the MH trailer connector and see if it spikes up for some reason when the exhaust brake engages.

Bob

[RiverBurt]

Originally Posted by BnR

Just thinking...is there anyway to engage the exhaust brake easily without actually starting the motor up and moving? Would like to test voltage at the MH trailer connector and see if it spikes up for some reason when the exhaust brake engages.

Bob

You can hook up a 12-volt battery directly to the solenoid and it will engage.

[BnR]

Originally Posted by RiverBurt

You can hook up a 12-volt battery directly to the solenoid and it will engage.

Might have to try that over the weekend...guessing I would need the key in the on position for the brake lights to come on?

I snooped around for a few minutes this evening and there is a red light in the dash with a decal around it. "BrakeMaster" "When the bulb is lit the brake lights on the tow vehicle are on"

So it appears it is a Brakemaster system....

Bob

[RiverBurt]

Originally Posted by BnR

Might have to try that over the weekend...guessing I would need the key in the on position for the brake lights to come on?

Logical assumption. But at least you’re not running or moving. Will logically isolate an electrical problem from a mechanical one!

My bet’s on mechanical, but we shall see.

[NevadaNick]

My boat trlr has electrically actuated disc brakes and my DP never had an issue. You likely have a short somewhere.

[FIRE UP]

Originally Posted by BnR

Might have to try that over the weekend...guessing I would need the key in the on position for the brake lights to come on?

I snooped around for a few minutes this evening and there is a red light in the dash with a decal around it. "BrakeMaster" "When the bulb is lit the brake lights on the tow vehicle are on"

So it appears it is a Brakemaster system....

Bob

Bob,
A very, very large percentage of the vehicles on the road today, including motorhomes, trucks, cars and more, actually have the brake lights energized with the brakes are applied, WITHOUT THE KEY IN THE IGNITION! Our '15 Jeep JKUR has brake light activation without the key in the ON position or even in the ignition. But, our other toad, an '11 GMC Sierra 1500 Extended Cab 4x4, MUST have the key ON in order to activate the brake lights. So, Not all cars/trucks/motorhomes etc. are built alike.

Now, as for testing the exhaust brake without the engine running, yes, you can do that. But, there's two sections to that operation. The electrical solenoid that, when energized, will open and allow air to proceed to the air control cylinder, that's connected to the exhaust brake valve. The electrical solenoid is a simple solenoid. Not much to it. It's open, or it's closed, no in between.

As for the air cylinder, pretty much the same only, just air is involved with its operation. You can disconnect the air line from the electrical solenoid and, if you have an outside source of air, you can then apply it to that airline that leads to the exhaust brake. When you do that, you can see that exhaust brake in action. But, even with that kind of testing, pretty sure you're not going to see anything that's going to relate to your problem. At least it would be pretty tough to correlate any exhaust brake valve action, with your particular problem.

This will be interesting to see just what the actual cause of your problem is. Do keep us informed.
Scott

[l1v3fr33ord1]

Bob-

The Roadmaster BrakeMaster system (link here) is for towed vehicles. It is not a trailer brake controller.

You also state that your boat trailer uses a surge brake. If so, it does not require a trailer electric brake controller. Correct?

This means you are only interested in making sure that the standard four signals, i.e.,

left turn/stop
right turn/stop
marker
ground

make it to the coach hitch connector and across the umbilical without problems. Have you tested for those signals at the hitch connector yet? It would help to know they work correctly even without the exhaust brake actuating.

The behavior the prior owner reported could be explained by a connection between the coach exhaust brake signal and the trailer electric brake controller wire. When the exhaust brake goes on, a full 12V would appear at the trailer electric brake controller pin on his trailer, causing the electric brakes to lock up.

Anyway, run some tests on the hitch connector pins and tell us what you find.

Consult your owner's manual for a diagram showing which pins have what signals, as the coach came from the factory. For a coach of your vintage, it is possible that the factory design came with separate turn and brake signals. If that is the case, someone may have wired in a 3-to-2 adapter (link here) to make the signals "standard" at the hitch connector pins. If so, the converter may have failed.

Finally, here is a link to wiring diagrams for "standard" connectors.