Troubleshooting Weak Brakes on Tandem Axle Trailer

Question

Question:

Sir: I have a Tekonsha P3 controller with a two axle trailer, four brakes. I have poor braking with the brakes fully adjusted. I ran the diagnostics on the P3 the battery voltage is 14.0, output voltage is 11.1 and output current is 9.5 amps. This is using the manual control level fully engaged. Your articles state that this indicates the magnets need to be replaced. Could you please advise how I can confirm this and make sure the controller is not faulty. Regards, Jim

asked by: Jim T

0

Expert Reply:

Hi Jim; I don't think it is the brake controller based on what you have already tested. However, depending on where you tested it could be the vehicle or trailer wiring. If you tested at the 7-way on your vehicle then that checks out. If you tested the wiring running out of the brake controller go ahead and test the vehicle 7-way for power on the brake output pin. If this checks out check for power at the brakes. If you have low power here there could be a short somewhere or a bad ground.

A bad ground is a fairly common problem and could definitely cause weak braking. It is always a good idea to check the ground or grounds on the vehicle and trailer. These should be secure on a clean, bare-metal surface. If all of this checks out you can test the brake magnets.

It is unlikely they're all bad, but nothing is impossible. For 10 and 12 inch brake assemblies, each magnet should read 3.2 to 4.0 amps at 12 to 13 volts. If the amperage readings are greater than the specified amounts, replace the magnets. If it is less, the leads are bad and the magnets should be replaced.

expert reply by: Robin H

0

Robin H.

1/27/2026

Hey Jim, what did you find when you checked the grounds and tested the brake magnets on your trailer? Knowing whether the readings matched the specs could really help others chasing weak braking issues with their Tekonsha P3 setups.

Jim T.

1/29/2026

@RobinH Robin, it turns out I had two problems. The brake magnets were in bad shape, lots of scoring and visual evidence of magnet overheating. They had maybe 25000 miles on them , so I had new brake assemblies installed. I never did measure the amperage or resistance of the magnets. I also replaced the 7 pin plug and pigtail on the trailer side with a Hopkins unit from eTrailer. I had a voltage drop from the 7 pin socket on the tow vehicle to the junction box on the trailer that the pigtail connects into. This suggested to me that the plug was not making good contact with the socket on the tow. vehicle. Cleaning the contacts did not help. After I installed the new pigtail, I noticed that the running lights on the trailer were quite a bit brignter than before, confirming there was a bad connection at the 7 pin socket. So it was two problems at once. I also think the problems were exacerbated by brake service at a sub standard shop, with little experience with trailers. I had the complete brake job done at a local reputable RV service shop. So one must pick quality shops for good service.

Answer 1

If you want to loosen the brakes on a drum braking assembly like the Dexter Electric Trailer Brake Kit part #23-26-27 you will need to spin the star washer down with the Brake Adjustment Spoon for Drum Brakes part #W80630.

view full answer...

Answer 2

Turning the wheel so that the teeth on the wheel move upward will expand the brake shoes against the inside of the brake drums. Moving the teeth downward will contract the brake shoes. You can see the adjustment procedure by clicking on the video…

view full answer...

Answer 3

The correct brake controller install harness for your 2017 Toyota 4Runner is the part #3041-P which installs by connecting to a white plug near the emergency brake pedal. I attached a picture that shows where you'll find the connector near the…

view full answer...

Answer 4

Hey Blake! Upgrading to 4 AWG wire is a great choice to run from your battery to the terminals on your power center. That'll help to minimize any voltage drop happening along the run of wire between the battery and the converter. You will use…

view full answer...

Answer 5

In regards to the Progressive Dynamics Mighty Mini AC/DC Panel and Converter/Smart Charger part #PD4045KA, the maximum size wire you can use on the battery terminal lug attached to the circuit board on the DC side is 2 gauge but this would be a super…

view full answer...

Answer 6

Hey Paul, thanks for reaching out! The divider inside the TorkLift PowerArmor Locking Battery Box #TLA7700L is welded in place so while it technically can be removed, it wasn't designed with that in mind. The best option we have for you is the…

view full answer...

Answer 7

The difference between the Class II and Class III hitches has to do with their Gross Trailer Weight (GTW), their Tongue Weight (TW), and their Hitch Receiver Size. Class II trailer hitch receivers have a 1-1/4 inch receiver and can be rated up to…

view full answer...

Answer 8

A 4-Way trailer connector has the basic lighting functions only; running lights, left turn signal and brake lights, right turn signal and brake lights, and ground. A 7-Way has these functions and a 12 volt circuit, a circuit for electric trailer…

view full answer...

Answer 9

It sounds like you are speaking of the wires for the brake magnets. If this is correct, you will need to connect one of the wires to the brake controller output wire on your trailer connector and the other wire will need to be grounded to a clean…

view full answer...

Answer 10

Since wire color codes are NOT universal, we always recommend wiring by function, rather than wire color. If you look at the Trailer Wiring FAQ article I have linked you to, you can see some diagrams showing the proper way to wire a vehicle and…

view full answer...

Answer 11

That's a very good question, we tend to be extra cautious and say to use 10 gauge wire because that would be more than enough. When you get into longer trailers that will end up using a lot of wire the heavier gauge wire becomes more necessary.…

view full answer...

Troubleshooting Weak Brakes on Tandem Axle Trailer

Product Page this Question was Asked From

Continue Researching