Trailer Brake Issue

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Trailer Brake Issue

Postby Capebuild » Mon Nov 14, 2022 11:14 am

Hello. I've got a 2000 # Dexter axle with electric drum brakes on my teardrop. The brakes were working and being recognized by the P3 Tekonsha controller for most of my recent cross country trip. On the return trip, for some reason, the Tekonsha controller stopped recognizing the trailer. All the exterior lights on the trailer are working fine, so the problem seems isolated to the brakes. All fuses seem intact, the controller in the auto is illuminating and on, but shows the red "no trailer connected" warning even though the trailer is connected. I put a volt meter on the 7 pin connector on the tow vehicle and with the meter's ground on the 7 pin's ground and the positive probe on the brake contact and the car's brake applied I'm getting a reading of almost 5 volts. With the arm on the brake controller applied (which applies the brakes on the trailer without having to step on the car's brake pedal), I get a reading of 12 volts when the arm is fully engaged. So this is telling me the brake controller is working and applying voltage / current to the 7 pin connector (although I'm not sure why I'm only getting 5 volts when the brake pedal is applied..... should I be getting 12 volts, as is what the volt meter is showing when the controller's arm is engaged??).... so that's my first question.

So provided the controller is functioning properly as far back to the 7 pin connector on the tow vehicle, any thoughts on why the brakes on the trailer are not functioning. It's all pretty much brand new wiring that is sheathed in loom. I've inspected it and do not see any breaks in the wiring. I've tested the continuity from the 7 pin connector on the trailer's cable (where it plugs into the tow vehicle) back to the junction box... testing both the blue wire and the ground for continuity.... no issues there.


any thoughts where to check next? I'm a little stumped on this, any help would be appreciated.

Thanks
John
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Re: Trailer Brake Issue

Postby GTS225 » Tue Nov 15, 2022 8:12 am

Well, they are electro magnets that actuate the brakes inside the drum. Have you performed a continuity check through them? Could also be that the wire(s) in the drum have been abraded.
I bought an older 24' Jayco a couple years ago, and discovered only one of the four brakes was functional., and ended up replacing all four brake assemblies.

Additionally, the Tekonsha controller is a proportional output, so it acts on internal sensors when you apply the foot brake, and outputs a lower voltage than applying the hand lever. That's why the instructions specifically tell you to mount it in line with the tow vehicle's direction of travel. Modern technology, ya know.

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Re: Trailer Brake Issue

Postby Modstock » Sun Nov 27, 2022 4:32 pm

Check the wiring underneath near the axle. I had my trailer brakes go out. Turns out that gravel had hit the wiring loom and broke the scotch-lock fastener near the axle.
Replaced with butt connectors and 2 layers of wire loom with lot's of tape wrapped fixed it .


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Re: Trailer Brake Issue

Postby Capebuild » Wed Nov 30, 2022 11:52 am

I am pulling my hair out over this.... still trying to figure out why my Tekonsha P3 is not recognizing the trailer when it is attached.

Question: If I disconnect the ground that's attached to the chassis (this is the ground that is comes from the 7 pin connector into the trailer's junction box..... I tapped off from that ground and made a separate ground to the trailer's chassis) .... if I disconnect that ground wire temporarily (see attached pict) ......and put a probe from a multimeter into the ground contact on the 7 pin connector and touch the other probe from multimeter to chassis frame, should the meter see continuity? It is. The only place I'm thinking there could be a ground connection to the chassis would be the brake's themselves, the ground wire and blue wire connecting to the electro magnets.... producing a ground connection to the chassis. Does this sound as it should be?

thanks.

John
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Re: Trailer Brake Issue

Postby Ottsville » Wed Nov 30, 2022 12:03 pm

Do your brakes have one wire or two going into the drums? I'm trying to remember what mine look like - I think there is only one wire which means they are grounded by the frame.

Can you just try a different brake controller and see if that recognizes the trailer?
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Re: Trailer Brake Issue

Postby twisted lines » Wed Nov 30, 2022 12:04 pm

Should the meter see continuity? It is.
It will if you grounded one light bulb, fan ect, to the chassis.
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Re: Trailer Brake Issue

Postby tony.latham » Wed Nov 30, 2022 12:05 pm

my Tekonsha P3


Have you tried hooking up to another trailer and ensuring it's not the controller? :thinking:

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Re: Trailer Brake Issue

Postby twisted lines » Wed Nov 30, 2022 12:08 pm

Ottsville wrote:
Can you just try a different brake controller and see if that recognizes the trailer?


Or put the controller in the trailer!
I bought a new truck years ago that had pinched trailer wires under the bed, that took magic to find, and blew fuses.
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Re: Trailer Brake Issue

Postby TimC » Wed Nov 30, 2022 12:16 pm

Hi John.

Have you tried connecting a 12v supply (battery) to the brake's wiring, at the brake? In other words testing to see if a 12v supply will actuate the brake without all the other electricals involved.

I would start at the brake and disconnect the two leads. Connect the leads to a 12v battery directly. Repeat on other brake. If they actuate then you've eliminated the brake as the problem. Just don't leave them connected more than a few seconds.

Sorry if you've already tried this but it is the spot I would start at. Next, does your Tekonsha light up when you plug it in and start the car?

Edit; Never mind, just saw your response below.
Last edited by TimC on Wed Nov 30, 2022 2:23 pm, edited 2 times in total.
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Re: Trailer Brake Issue

Postby Capebuild » Wed Nov 30, 2022 12:18 pm

Ottsville wrote:Do your brakes have one wire or two going into the drums?

It's a Dexter axle with electric brakes. There's 2 wires going to the brakes. One is ground and the other is the blue brake wire...both coming from my junction box.

[/quote]
twisted lines wrote:Should the meter see continuity? It is.
It will if you grounded one light bulb, fan ect, to the chassis.


There's nothing grounded to the chassis (no fan or lights, etc.).... all grounds connections are originating from the "mother" ground (either from the ground in the junction box from the tow vehicle's battery or from the house battery). Neither of those two circuitries have anything to do with one another.

tony.latham wrote:Have you tried hooking up to another trailer and ensuring it's not the controller?

That is a great suggestion.... I had thought of that previously and I should probably make an effort to do that.

Thanks all for the help on this. Over the weekend I rewired the 2 brakes and after that the P3 controller did recognize the trailer. I thought all was good and took it out on a straight away portion of a road to set the power on the controller. After one try of setting it, the controller's evil red light came on saying "No Trailer Attached". Very frustrating.

John
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Re: Trailer Brake Issue

Postby Capebuild » Thu Dec 01, 2022 8:36 am

TimC wrote:Have you tried connecting a 12v supply (battery) to the brake's wiring, at the brake?


Thanks, Tim..... When I had the hubs disassembled (and at one point when the controller was recognizing the trailer after I rewired it all) I had Jean step on the brakes in the TV and I held a metal washer up to the electro magnets in each hub. The washer stuck to them, so at one point, at least, it seems the electro magnets were doing their job.

I had received some "Tech Bulletins" from Tekonsha....one on how to test the controller and one on how to test the trailer's wiring. The controller's tests all passed so at this point I think I can rule out the controller being the issue. I'm going to go back to the brakes today and do some testing again on the electro magnets... somehow I think the issue is there. Will keep you posted. This all is certainly a head scratcher
:x :?
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