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Open Roads Forum  >  Tech Issues

 > How to Activate Brake Magnets

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enahs

Washington

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Posted: 09/13/11 01:15pm Link  |  Print  |  Notify Moderator

What did I expect? I would expect to hear the magnets slap the drums. Correct, center is not ground — though it and other pins give a to ground light on the meter. But the question remains — should I be able to activate the magnets this way? I take it the consensus is that it should work. Crossing #2 and #4 should give me brakes.

* This post was edited 09/13/11 01:27pm by enahs *


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fpresto

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Posted: 09/13/11 01:40pm Link  |  Print  |  Notify Moderator

You may not hear the magnets. A quick check, although it works better with two people, is a simple compass placed near the wheel. When the magnets activate the needle will swing.


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othertonka

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Posted: 09/13/11 01:46pm Link  |  Print  |  Notify Moderator

You need to pull that emergency brake pin, to see if it works now before you ever have an emergency. If it breaks or won't come out, what makes you think it will work if you had a "Break Away" later on when pulling down the highway? If you can't pull it by hand, get a new break away switch and replace the old one. As for the magnets, you can jack up each axle and turn the wheel after you activate the magnets and see if you get a brake application at that wheel, then do all th others.


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RoyB

King George, VA

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Posted: 09/13/11 02:34pm Link  |  Print  |  Notify Moderator

One quick comment on pulling the BREAK AWAY switch. Might be a good idea to pull the trailer cable from the truck. This may not be good on your brake controller.

I find it best to go to electrical box under the trailer close to the batteries and remove the lid of this electrical box. Here you will see all of the color wires coming from the trailer plug that connects the trialer frame circuits. They will be connected together using a large twsit lock wire nut. These color wires will connect up "color for color"

I found it much easier to disconnect these wires and connect a small aligater test lead from the BLACK wire to each of the lights wiring colors GREEN-BROWN-RED to see if they all work properly. (NOTE DO NOT clip the battery voltage to the WHITE WIRE which is ground potential or sparks will fly and you may blow a fuse somewhere.) All of the other wires either go to LAMP or to the BRAKE MAGNETS. See list beow for wire functions..

The wire colors are as follows:

WHITE - GROUND (Goes to frame ground inside the trailer wiring)

GREEN - RUNNING (MARKER) lights

BROWN - Right Hand Signal Lights

RED - Left Hand Signal Lights

YELLOW - Backup lights (Not used on RVs (Will not be connected to anything)

BLACK - Positive (+) 12VDC from the Trailer BATTERY

BLUE - Trailer Electric Brakes

The RED wire and the BROWN wire is also the STOP LIGHTS depending on which position the turn signal lever on the truck is in.

Couple of comments about the Brake Magnets - There should be two wires going to each brake magnet BLUE and WHITE are usual colors. Even though the WHITE goes to frame ground it is a good idea to always have the WHITE also going to the return wire of the brake magnet and not use frame ground at the brake magnets for ground return..

Each BRAKE MAGNET will draw 3 AMPS when a full 12VDC is applied.

If you jack up a wheel to test the brake magnets just pull the break-away plunger and it should apply 12VDC from the trailer battery to the all of the BRake Magnets. You should have the trailer to truck cable disconnected doing this test. The brake action may not immediately snap into position as some may require an 1/4 to 1/2 turn movement before this happend (A mechanical thing)

Each brake magnet should emit a low tone hum noise that you can hear . they also create a localized magnet field which you can see activity using a compass.

Also note the newer trucks 2009 and up having OEM installed brake controller sample alot of things in the truck such as brake fluid pressure, speedometer sample, etc. They are also designed to not send a brake control voltage to the brake magnets by pushing the brake pedal if you are not moving at least 5-10MPH. The Manual brake controller lever should work under all conditions. I have personally tested this claim and it is indeed they way it is on my 2101 F150 Ford truck with OEM Brake controller. I have also confirmed this with FORD.

Also etrailer.com has all kinds if useful trailer drawings and trailer parts along with install instructions some with video's. Great prices on everything as well... Was very useful to me poking around my trailer wiring...

This was my method of testing the 7-wire cable circuits - I'm sure others will do it differently... My tests were run on my Starcraft 14RT OFF ROAD POPUP and my Flagstaff 8528RESS Fifth Wheel trailer earlier this year..


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HuckleberryHunter

Issaquah, WA

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Posted: 09/13/11 02:47pm Link  |  Print  |  Notify Moderator

fpresto wrote:

You may not hear the magnets. A quick check, although it works better with two people, is a simple compass placed near the wheel. When the magnets activate the needle will swing.


x2 I can't hear mine, but the compass shows me they are working.

wittmeba

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Posted: 09/13/11 03:32pm Link  |  Print  |  Notify Moderator

Its not the 7 pin thats hot - it is the 4 pin. You should be able to touch it to the 2 pin and have brakes. The 7 pin is an auxiliary and sometimes use for backup lights.

Be sure you have a fully charged battery or you wont get a full/true reading.






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Posted: 09/13/11 03:54pm Link  |  Print  |  Notify Moderator

And while you are checking the magnets.......should be checking brake function.

Yes ...a compass will deflect when magnet is energized but that doesn't mean brakes are working.
Jack up a wheel, check brake function and adjust brakes.

Also, that 'emergency pin'.....hard to remove ???? Then now is the time to remove it and make sure contacts are not corroded.....should feel some resistance when pulling pin BUT it shouldn't be 'hard'. Best time to replace switch is now....cheaper also.

enahs

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Posted: 09/13/11 07:17pm Link  |  Print  |  Notify Moderator

Thanks for all of the comments — they are very much apprreciated. I've been at this stuff for a long time — and I know the break-away works. One wheel has no brakes (when jacked and spun), all connections appear good; but I am proceeding to redo everything. BTW, all the brakes, drums, and backing plates were new less than 1000 miles ago. There is a problem with one brake — and it's frustrating to track it down. I'll post back and let you know what I find. Meanwhile, linking #2 and #4 does not activate the brakes on my Arctic Fox 27-5L.

* This post was edited 09/14/11 07:41am by enahs *

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