What Ohms Should Trailer Brake Magnets Be?

Question

Question:

When I have my brake controller connected and I apply my brakes, the trailer brakes grab regardless of the gain setting. I checked the ground and its good. I checked the resistance at each brake and one reads 2.0 ohms and the other reads 2.8 ohms. Single axle.

asked by: Patrick F

0

Expert Reply:

Assuming that when you tested the resistance of the brakes you were testing the two wires on each magnet and getting 2.0 and 2.8 ohms the magnets on your trailer are not working correctly and will need to be replaced.

For 7" brakes you should get 3.8-4.0 ohms, and for 10-12" brakes you should have 3.0-3.8 ohms.

If the brake shoes themselves are good you can replace just the magnet using 7" # AKBRKR-M7, 10" # AKBRKR-M10, or 12" # AKBRKR-M12.

If the shoes are needing replacement as well you will need to go with 7" braking assembly # AKEBRK-2, 10" # AKEBRK-35-SA, or 12" # AKEBRK-7-SA.

I included videos for the products mentioned for you to take a look at.

expert reply by: Samuel C

0

Mike

7/6/2024

I tested resistance at the 7 pin connector: between brake terminal and ground. I got 1.7ohms which I think means it would pull about 7 amps (between the 2 brakes) if I understand correctly. Sound right? Thanks.

Samuel C.

7/6/2024

@Mike You're going to need to test at the magnet, as testing at the 7-way adds in a lot of additional wiring leading to weird results. You should have more resistance than 1.7ohms, that is almost half of normal readings, though you may be getting a weird reading based on where you're testing (at the 7-way and not directly to the magnet)

Johnc. B.

3/16/2025

@SamuelC

Kate F.

3/17/2025

@JohncB Hey there John, did you have a question? I don't see that one was written...

Jason Y.

1/15/2025

Hey Sam, My rear wheel drum on my Coromal Element tandem caravan is heating up after a short trip. The other 3 drums are fine. I have checked the ohms and they are all between 3.1-3.3. I have adjusted the shoes, checked the bearings. I am lost now?????? Do you have another suggestion as to what could be the problem mate Please

Kate F.

1/15/2025

@JasonY Hello Jason. I am sorry to hear that one of your drums is heating up. Since you already checked your bearings and adjusted your shoes, it could be a sticking magnet. You will want to jack the trailer up and manually spin the wheel while someone else activates the brake controller to ensure it releases fully when power is off. If that turns out ok, I would check the magnet for glazing/contamination. If it is glazed it will look smooth and polished instead of that rough matte surface, if you are unsure I would compare it to one of the ones that is working correctly. Also inspect the drum, if it is glazed over it will cause uneven wear or grooved patterns from excessive contact with the drum. If it is slightly glazed you could use some 120-150 grit sandpaper to LIGHTLY sand the magnet, if it is too worn you will need to replace the brake shoe, or at least the magnet. One last thing to look over is the brake wire that there isn't any damage and the connection is good. Let me know how things turn out. Feel free to send me pictures of the drum and brake shoe if you need a second set of eyes. I know you thought you were asking Sam the question, he is now in charge of our training classes so he can spread his great knowledge with the rest of the etrailer employees, and he is doing a Fantastic job at it too!

Jason

1/16/2025

@KateF Thanks so much for your reply. I checked the ohms on all 4 magnets and they all sit at 3.2. I will check the magnet as you said and see if I can notice anything you mentioned. Thank you

Answer 1

The first thing you will want to check is the output voltage on the brake controller. If it is set too low, it will not send enough power back to engage the trailer brakes. For testing purposes, it is easiest to set it to full power. Using a meter or…

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Answer 2

It is normal to have continuity between the brake(blue) wire and ground(white) wire. The electric trailer brake is an electromagnet when it has power it attracts to the steel inside the hub/drum. If you are having issues with your trailer brakes…

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Answer 3

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Answer 4

Thanks for the Picture. What you have there is a 6 on 5-1/2" hub for a 3,500 lb axle. We do have a replacement hub for your Truryde RVD-H-65535 hub. The correct replacement will be part #AKHD-655-35-EZ-K. This will include the hub, bearings,…

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Answer 5

Brake magnets for 12 inch brake assemblies should have an ohms reading that falls within the range of 3.0 to 3.8. The 3.7 ohms reading on your brake magnets does not indicate that the brake magnets need to be replaced. If you are experiencing…

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Answer 6

Hey Marty, if you used the Dexter Bronze Bushings part #K71-291-00 with a non-wet bolt and everything was greased heavily it's going to work really well. The bronze will last longer than plastic but if not maintained (like anything) they can fail…

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Answer 7

The .C code you are seeing on the display of your Pilot 2-6 Brake Electronic Brake Controller #80550 that you referenced indicates that the brake controller senses that it is connected to a trailer. Since yours is still functioning but always has…

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Answer 8

I recommend using at minimum a 12 gauge wire like #12-1-1, but preferably 10 gauge wire like #10-1-1. When you try to run 12v power for electric brakes through a thinner 14 gauge wire to power something like your brakes it overloads the wire and…

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Answer 9

According to my research the Transcom part 21334TC is an oil seal with a 2.125" inner diameter and a 3.372" outer diameter and the Transcom part 2133TB is a grease seal with a 2.125" inner diameter and a 3.376" outer diameter.…

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Answer 10

I reached out to my contact at Dexter Axle and she said that the Dexter Electric Trailer Brake Kit #23-47-48 have a coil resistance of 3.9 ohms per magnet. When it comes to wire size we recommend at least 10 gauge wire like part #10-1-1 (sold by the…

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Answer 11

If you have a 3,500 lb Dexter EZ Lube spindle we for sure have the parts needed to add brakes to your trailer or replace ones that you currently have. For a set of 10 inch assemblies that would fit and work well you'd want the part #AKEBRK-35-SA…

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Answer 12

Before you choose brakes or bearings you should verify what's currently on your trailer. If it is a 3,500 pound axle part #AKEBRK-35-SA will likely fit if the trailer has electric drum brakes. Both sides are included and labeled. They're also…

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What Ohms Should Trailer Brake Magnets Be?

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