View Full Version : Brake lights & Trailer brakes.

04-04-2010, 09:34 PM
I've presented this scenario to a few folks and got varried responses. Let's try it here

I pull a 24 ft cargo trailer with electric brakes and a Tecnosha controller.

Simple part: Apply the brakes in the coach and the trailer brakes are applied.

I've been told by the trailer dealer that the trailer brakes work off the motorhome's brake lights. Makes sense, right?

I then noticed that when the engine retarder is engaged the coach brake lights come on. I asked the triler dealer if that means the trailer brakes are applied when the engine retarded is engaged. His response was "I would think so. If you are slowing the coach you want the trailer brakes to be applied as well." Makes sense too, right?

Now the big question is this. Does the coach know the difference between the brake lights and the hazzard flashers? Are my trailer brakes being pulsed with the flashers when I'm climbing a steep grade at 25 or 30 MPH?

Since I don't know the answer, I have been adjusting my brake controller to the off position when I have to use the flashers going up a hill. I get nervous when I have to use the flashers going down hill.

Your thoughts?

04-05-2010, 02:19 AM
In all my 56 years I've never heard that one. The electric brake on your trailer is just a big DC electromagnet. Your controller is a variable resistor that applies a different amount of DC Voltage to the trailer magnet that applies the brakes. The switch that activates your brakelights does only that. Light on/Light off. When you press on the brakepedal your controller senses the position of the pedal and sends the amount of voltage that the controller is set to deliver down a wire just for the trailer brakes. Your connecter to the trailer has seperate wires for turnsignals, lights, brakelights, sometimes the turnsignal bulb is used as a brakelight, depending on how yours is setup, often another wire for 12 Volts DC to power your lights inside the trailer from the battery in your coach, and finally, another wire to your electric brakes on your trailer. What a run-on sentence! You need a different trailer guy!

04-05-2010, 08:12 AM

Thanks, your explanation seems the most logical. Perhaps that's why the guy at the trailer shop is at the desk and not in the garage':wink:'

Considering what you have told me, should I assume that the trailer brakes are not applied when the engine retarder is engaged?

04-05-2010, 11:08 AM
when you apply the brakes the controler [or whenever the controler is controling] should indicate the the brakes are applied, some lighted signal, strength,etc. i would think if there is no indication showing up on the controler then it should not be sending any voltage to the tow trailer.that is ofcoures if the brakes are wired up to the controler first.

04-05-2010, 07:55 PM
I'll bet the brakes on the trailer are applied by tongue pressure to the hitch. Check and see if you have a sleeve that the trailer tongue fits into then runs the rest of the distance( in a larger sleeve) to the hitch. It's been my experiance (20 years selling trailers) that this is a demand build feature on all small trailers weather they are set up for elec. brake systems or not.

Part of the reasoning behinde this that a lot of folks will pull barrowed or rented trailers without the lights hooked up or have the abitity to hook them up.

This feature would explain why your trailer brakes apply when the retarder kickis in. No power required.

04-07-2010, 02:03 AM
Nanaeve gave you the correct information on how electric brakes work from your controller to your trailer. Flashers don't have anything to do with the brakes on the trailer.