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Old 05-29-2008, 08:16 PM   #1
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New electric brakes don't

Just got one of my new Dexter axles mounted. When I hook up the brakes they do not activate. I am suspicious the brake problem developed before axle was replaced. Shortly before I changed the axle while towing with the old axles I tried to apply the trailer brakes manually and I did not feel the trailer brakes activate. I have power coming into the trailer from the brake controller to the 7 way. I know brakes are hooked up electrically in series. I am suspicious that when one brake out of 4 is disconnected and I hook a test light between the leads the test light does not light, but, when I ground the test light to the frame and probe either the black or white lead coming out of the belly of the trailer the test light goes on for either lead. When all 4 brakes are hooked up I still get nothing. Shouldn't one lead be negative and not light? I don't know for sure if the old 2 brakes are working as the wheels on that axle are on the ground. I suspect a short or a bad ground somewhere possibly at the 7 way connector box in front of the trailer. I know the brakes were working earlier this year, and I didn't change anything. Any suggestions where to start poking aroound? I know it is unlikely that both brakes on a new axle don't work, but can I test them by hooking up a 12 car battery to the leads and see if they activate. I am also assuming the new electric brakes don't need to be adjusted before 1st use?.
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Old 05-29-2008, 08:47 PM   #2
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If you have a battery in the trailer take the 7 way plug and while holding it so as to look at the end with the tab at 12 oclock. With at least one wheel jacked up have someone spin that wheel and while it is spinning with a piece of #12 wire jump between the 11 and 7 oclock connections on the connector. If the wheel stops the brakes and trailer wiring are OK.

Do not use a smaller piece of wire as the full brake load will be in that wire and it may melt in your hands if you are using a lighter gage.

The brakes are wired in parallel. The only way one brake could cause a complete failure is if one of the magnets was shorted to ground, highly unlikely with new axles.

As for the wiring of the brakes themselves it does not matter which way you connect the 2 wires. DC circuits, IE the magnets, are not polarity sensitive.
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Old 05-29-2008, 09:15 PM   #3
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Quote:
Originally Posted by HowieE
If you have a battery in the trailer take the 7 way plug and while holding it so as to look at the end with the tab at 12 oclock. With at least one wheel jacked up have someone spin that wheel and while it is spinning with a piece of #12 wire jump between the 11 and 7 oclock connections on the connector. If the wheel stops the brakes and trailer wiring are OK.
I will try that, but I'm not sure if it will tell me much I do not already know, which is: I have electricity coming from the brake controller into the trailer.

What I do not know is why both the black and white leads coming out of the belly pan for the brake hook ups are hot when the brakes are applied. One should be a ground should it not? The test light lights up when grounded to the frame when either the black or white lead is tested and the brake pedal is depressed or trailer brakes applied at the controller. When the test light is connected between the black and white leads and the brake pedal or controller applied the light does not light. When the brakes are not applied from the TV there is also no light. This does not sound right to me and I suspect a wiring problem between the 7 way and brakes. But I am not 100% sure.

Can I just hook up a car battery or 12v battery charger to the brake leads on the new axle to check the brakes themselves are OK?
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Old 05-29-2008, 09:30 PM   #4
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One line needs to go to ground. If your ground line is not connected, then both lines will show voltage in reference to ground. Determine which line is bringing controller output to the brake unit and ground the other one. As noted before your brakes should be connected in parallel, not in series. Look at the diagram I posted on ur other thread yesterday.
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Old 05-29-2008, 09:36 PM   #5
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Electric Brakes for Complete Idiots

Quote:
Originally Posted by HowieE

The brakes are wired in parallel. The only way one brake could cause a complete failure is if one of the magnets was shorted to ground, highly unlikely with new axles.
I was told earlier the brakes were wired in series like those pesky christmas lights when one bulb goes they all go.

The magnets on the new brakes should be good, but I still have one 37 year old axle, with 37 year old brakes, still on the trailer. Could a magnet on the old axle be shorted to ground and that is why both my leads to the new brakes test hot? And if so and the brakes are wired in paralell I could disconnect the leads to the brakes on the old axle and then the brakes on the new axle should work? Do I understand that right?
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Old 05-29-2008, 09:44 PM   #6
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Ground wire

Quote:
Originally Posted by Excella CM
One line needs to go to ground. If your ground line is not connected, then both lines will show voltage in reference to ground. Determine which line is bringing controller output to the brake unit and ground the other one. As noted before your brakes should be connected in parallel, not in series. Look at the diagram I posted on ur other thread yesterday.
The only way I know of to determine which line is bringing controller output to the brake is black is hot and white is ground. So If I hook connect the black lead to one lead going to the brake and ground the other lead from the brake to the trailer frame the magnet should activate right?

Then can I assume I have a bad ground somewhere and start playing electric detective to find the bad ground?
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Old 05-29-2008, 10:35 PM   #7
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Marshall, check your "Master Ground" for continuity. For more info, view this video:

Ground wire 411 - Airstream Life
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Old 05-29-2008, 11:54 PM   #8
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Marshall;
Go to the hensley mfg web site, click the "tru control" tab. Read the "Better braking report". May help you out.
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Old 05-30-2008, 06:55 AM   #9
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Brakes are in parallel. Not in series

Connect each black wire to the hot side of the wire coming from the truck and the other white connection to a good ground on the trailer. If all else fails, run a good ground lead to each of the brakes and connect the other end of that wire to the best trailer frame ground spot you can make by scrapping off the rust and drill and tap a good hole. Coat the connection with silicone sealant after you make sure it is good. Another place to make the ground connection is to the ground wire in the cable coming from the Truck or the trailer battery ground.
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Old 05-30-2008, 06:56 AM   #10
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Quote:
Originally Posted by Lumatic
What I do not know is why both the black and white leads coming out of the belly pan for the brake hook ups are hot when the brakes are applied. One should be a ground should it not? The test light lights up when grounded to the frame when either the black or white lead is tested and the brake pedal is depressed or trailer brakes applied at the controller. When the test light is connected between the black and white leads and the brake pedal or controller applied the light does not light. When the brakes are not applied from the TV there is also no light. This does not sound right to me and I suspect a wiring problem between the 7 way and brakes. But I am not 100% sure.

Can I just hook up a car battery or 12v battery charger to the brake leads on the new axle to check the brakes themselves are OK?
Yes you can but that will nly thest the brake itself. Sounds like we have to prove the wiring also.

Both wirres are brought to the brakes because Airstream returns the ground side back to a common ground point.

The fact that you have old and new on the trailer lets back up a bit. Open all the wire connections on all the brakes. Now test for power at each brake. You should only see power on one wire at each brake. If you see power on both leads I would look into the umbical cord plug for a short between power and gound. If you only have power at one lead per brake go ahead and connect one brake at a time and while someone is spinning that wheel test from the controller.

If you come to a brake that is not working as expected you have defined the location of the problem.
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Old 05-30-2008, 08:54 AM   #11
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Thanks yall I have followed up on everyones ideas and things are slowly getting clearer in my head.

One idea that has not been mentioned, but I might as well, disconnect the umbilical and check the break away while I'm at it.

If I disconnected all the brakes and hooked the leads going to a single brake direct to a car battery or charger to test the brake could I send too much amps and damage the magnet?
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Old 05-30-2008, 09:25 AM   #12
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You can test as you described, but don't leave the current on for more than a few seconds. the magnets use a lot ofpower and will overheat if left on. You can also test the break-away switch, but likewise don't leave it activated for more than a few seconds.
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Old 05-30-2008, 01:24 PM   #13
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Quote:
Originally Posted by Lumatic
If I disconnected all the brakes and hooked the leads going to a single brake direct to a car battery or charger to test the brake could I send too much amps and damage the magnet?
No The magnets are self limiting as to the current they will pull. That is what I suggested a few posts back. Useing the trailer battery and making a connection at ostion 11, power and 7, brakes will apply the brakes. But now that you have added information I would again suggest that you disconnect all the barkes and work you way through the system one brake at a time to locate the original problem,

Each magnet will draw about 3.5 amps when direct voltage is applied. That is way I mentioned using at least a #12 wire for any test when appling direct voltage to the system. The brake controller amost never applies full voltage under normal usage. Full voltage will be applied if you close the manual switch on the controller but the duration of your testing, either while using the trailer battery or the manual switch on the controller, will not cause a problem
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Old 05-30-2008, 03:02 PM   #14
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Duh?

Quote:
Originally Posted by HowieE
Useing the trailer battery and making a connection at ostion 11, power and 7, brakes will apply the brakes.
Help me understand this somebody


I checked the 11 o'clock position on the umbilical while disconnected from TV and connected to trailer. This position tests hot with a test lamp. However, the diagram in the service manuasl show this position is the ground line and identifies the center position and the charge line. The center position does not test hot. Are these results as they should be? The 7 o'clock postion is the correct postion for the brake controller line.

This is exactly why I earlier assumed the ground and charge line had reversed wiring. To me the implication was the ground line (11 o'clock) should be negative and the charge line position (center) should be positive. Now it appears that my wiring tests out as Howie described and this polarity is normal. Vat is das?
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