Breakaway switch and brake lights

[bearwayne]

Yesterday, I replaced the cable that connects the 5th wheel to the 7 pin connector on the truck. Luckily, the cable I ordered used the same color scheme as the existing cable (I tested old and new cable with a multimeter) and after connecting everything, the tail lights, turn signals, brake lights and running lights all worked as they should.

Then I decided to test the breakaway switch. I could not tell that anything happened when I pulled the pin. I checked the wire from the breakaway switch and I had voltage. Today, I tested it again after filing the contacts in the breakaway switch with a nail file. Again I had voltage (I think it was 12.5V), but the brake lights don't come on and I don't hear the brakes humming. I reattached the cable to the tow vehicle, and I can hear the brakes humming when the brake pedal is pressed as well as when the manual switch is pressed on the brake controller.

Shouldn't the tail lights come on when the breakaway switch is tested? I suspect that not enough current is passing through the breakaway switch to activate the brakes and the brake lights (I don't have an ammeter to test it.) I have already ordered a new one from Amazon.

[Bobbo]

I think it was the steel rims making the compass deflect. The magnets are electromagnets. They are not magnetized unless energized by the controller. If they were magnetized all the time, the trailer brakes would stay locked up all the time.

[bearwayne]

I did a little research this morning and now I understand why the breakaway switch does not connect to the brake lights. What I didn't realize is that the brake lights are controlled via the turn signal connections and is actually managed by the tow vehicle. I found a wiring diagram at ledtrailerlights.com that labeled those pins as "left/brake light" and "right/brake light" whereas the diagram that came with my new cable labeled those pins "left" and "right" which end helped confuse me!

As for the compass test, how close to the wheel does the compas have to be? I just tried it and with the breakaway pin pulled, the needle was pulled from North to Easr-West when I placed the compass on the outside of the wheel in the well of the rim. Trouble is, it did the same thing with the pin back in place on the breakaway switch. So, I assume it was the effect of the magnets moving the needle and not the 12VDC flow.

[rrupert]

westend wrote:
Yeah, you should get some more current through the switch to make the lights work. I'd suggest to install another battery on your truck.

I don't think you read any of the above posts.

[dougrainer]

westend wrote:
Yeah, you should get some more current through the switch to make the lights work. I'd suggest to install another battery on your truck.

NO lights ever come on when the Breakaway switch is pulled loose. Besides, the lights are minimum amp draw compared to 4 brake magnets. Doug

PS, what good would an extra battery on your TRUCK do if the Break-Away switch is pulled?????????? That means the trailer is not connected to your truck anymore, so what good would an Extra Truck battery do? The Break Away is engaged by the TRAILER battery.

[westend]

Yeah, you should get some more current through the switch to make the lights work. I'd suggest to install another battery on your truck.

[SoundGuy]

bearwayne wrote:
Shouldn't the tail lights come on when the breakaway switch is tested?

Think about it - "testing" the breakaway switch system by pulling the lanyard is no different than the lanyard pulling free under actual circumstances when the trailer has broken free from the tow vehicle. In the unlikely event that disaster has occurred what would be the point in the trailer's brake lights illuminating as it hurtles down the road trying to kill anyone in it's path? :R The sole purpose of that breakaway system isn't to save your trailer but to minimize damage it can cause to others ... and illuminated brake lights aren't going to contribute to that goal in any way. 😉

[DrewE]

Bobbo wrote:
You will have to take our word for it. The brake lights and the brakes are 2 completely separate circuits. Your tow vehicle activates both when braking. Think about this, the brake lights are on or off. They are all or nothing. They don't get brighter the harder you press the brakes. The brakes are proportional. The harder you press the vehicle brakes, the more power is sent to the trailer brakes, the harder the trailer brakes are pressed. The breakaway switch only activates the brake circuit. It is not hooked to the brake light circuit so they don't illuminate.

If the cars following you when you have your trailer break away can't tell there is a problem, the brake lights probably won't help.

Furthermore, on trailers, the brake lights are on two separate circuits and are also the turn signals. You really wouldn't want your left brake flipping on and off whenever your left turn signal is on.

[Bobbo]

You will have to take our word for it. The brake lights and the brakes are 2 completely separate circuits. Your tow vehicle activates both when braking. Think about this, the brake lights are on or off. They are all or nothing. They don't get brighter the harder you press the brakes. The brakes are proportional. The harder you press the vehicle brakes, the more power is sent to the trailer brakes, the harder the trailer brakes are pressed. The breakaway switch only activates the brake circuit. It is not hooked to the brake light circuit so they don't illuminate.

If the cars following you when you have your trailer break away can't tell there is a problem, the brake lights probably won't help.

[bearwayne]

Thank you all for your replies! I will try the compass test and report back. I think I understand why the brakes don't hum with the breakaway switch activated vs the brake controller--DC vs. PCM. The brakes don't click because the wheels aren't moving. I'm not yet convinced about the brake lights but if the compass test shows the brakes are activated, I'll be happy! 😉

[dougrainer]

IF you get a spark/arc when testing the BLUE brake pin, there is current going to the magnets. OR, connect to your truck, pull the breakaway and attempt to pull forward. IF the brakes are operating the tires will lock and skid. Doug

[red31]

At the bottom of this page is an electric brake animation, you can see the magnet needs to move (the wheel needs to turn) for the brakes to activate

http://www.axleinc.com/electricbrakesdrums.html

[RoyB]

I was testing my brake drum drag and noticed sometimes when I engaged the electric brakes nothing happened until I turned the wheel about a quarter turn...

Must be some kind of mechanical thing has to happen first ???

Also on my fifth wheel I hear the tone when the electric brakes are engaged but on my POPUP trailer I don't hear a tone...

I know the brakes were engaged as I was using a compass I carry in my glove box and the needle was changing when the brakes were engaged...

Roy Ken

[Gdetrailer]

bearwayne wrote:
Yesterday, I replaced the cable that connects the 5th wheel to the 7 pin connector on the truck. Luckily, the cable I ordered used the same color scheme as the existing cable (I tested old and new cable with a multimeter) and after connecting everything, the tail lights, turn signals, brake lights and running lights all worked as they should.

Then I decided to test the breakaway switch. I could not tell that anything happened when I pulled the pin. I checked the wire from the breakaway switch and I had voltage. Today, I tested it again after filing the contacts in the breakaway switch with a nail file. Again I had voltage (I think it was 12.5V), but the brake lights don't come on and I don't hear the brakes humming. I reattached the cable to the tow vehicle, and I can hear the brakes humming when the brake pedal is pressed as well as when the manual switch is pressed on the brake controller.

Shouldn't the tail lights come on when the breakaway switch is tested? I suspect that not enough current is passing through the breakaway switch to activate the brakes and the brake lights (I don't have an ammeter to test it.) I have already ordered a new one from Amazon.

No, the brake lights are not wired to the breakaway switch..

No you will not hear any "humming" at the brakes, the break away switch sends pure 12V DC to the magnets.. There is no way pure DC will "hum" in any way shape or form..

You can check to make sure your brakes are working when the break away switch is activated by using a compass, by jacking up the wheels and trying to turn them by hand.. or my favorite way, use your vehicle (with the trailer to vehicle cable disconnected) and see if the brakes slide the tires..

[boogie_4wheel]

The wheel brakes and brake lights are separate circuits. Actually the brakes lights are divided into left and right side...
The breakaway switch will not activate any lights, only supply the brake magnets with the trailer battery voltage.