Trailer brakes weak

[mtruckert]

I have a 2019 Chevy Tahoe with towing package/brake controller and a 2019 Keystone Outback Ultralite (260UML) trailer. I recently brought the trailer in to a Goodyear Tire shop to have the bearings and brakes inspected, the axles repacked and new tires installed. When I picked up the trailer, the brakes were weak…so I swung right back in to the shop assuming they spooned the brakes in to get the drum off. After multiple attempts to adjust the brakes correctly, they were still weak. Through the entire process, I caught the technician lying several times and just had no faith in what I was being told. So I took the trailer home.

Since the technician stated the pads were down to 4/32nd of an inch (which in retrospect was another lie), I decided to buy all new brakes. I ordered new Dexter 10in 3.5K LH Elec Nvr-Adj Drum Brakes (Model Numbers 23-468/23-469); (full mounting kit) for all four wheels. I installed the brakes and repacked the bearings. Test drove the unit and the brakes are still weak even after MULTIPLE braking attempts to ensure the new brakes adjusted themselves up nice and snug to the drum. Next I jacked up the wheels and hooked the Tahoe up, and when the brake controller is squeezed the spinning wheel stops immediately and you cannot turn it by hand.

During the install of the new brakes, I verified that there was no grease or oil on the drums and the drums were not scored/grooved. The brake pads and magnets were brand new and sparkling clean….so no issues with them. The trailer is empty so it is not overloaded. I also checked the electrical connections and voltage/amps as followings:

Note – I cannot test the voltage/amps directly at the brake controller without pulling my dash apart since the controller is part of the original vehicle and not an aftermarket item.

Trailer Harness terminal block on Trailer – 12.56 Volts brake/neutral connection. I did not test amps at the terminal block since my meter only reads up to 10 amps DC and I should get 12 Amps.

Next I checked each wheel connection with the below readings:
Left Front Wheel – 9.5V and 2.47A
Left Rear Wheel – 9.6V and 2.5A
Right Front Wheel – 9.6V and 2.2A
Right Rear Wheel – 9.8V and 2.25A

Note – For the wheel measurements, when the controller was initially engaged the voltage readings would climb from 0 to ~7V and then up to the final reading of ~9.6V after being held on for 5 seconds or longer.

Prior to taking the trailer into the Goodyear shop, with the gain set at 7 out of 10, the unloaded trailer would just about lock up the brakes at 20 mph on flat dry pavement…as designed. Now the brakes are barely noticeable when the controller is engaged.

I have not been able to find anyone that I know who has a tow vehicle with a brake controller that I can borrow to test the controller.

Questions – Is the voltage drop from 12.56V at the terminal block to ~9.6V at the brakes and the slightly lower amp readings (should be 3 amps per Dexter’s literature) at the brakes, enough to cause the weak braking that I am currently experiencing? Also, the voltage/amps recorded at the peak readings with the brake controller held in the fully engaged position.

__________________
Matt and Judy wife of 34 years
2019 Chevy Tahoe LT w/ Towing Package
2019 Outback Ultralite 260UML

 

[JRTJH]

First, did you adjust the brakes manually when you initially installed them? If not, you may not be able to achieve "maximum adjustment" with the self adjusting feature. It takes A LOT of stops to get the "self adjusting mechanism to tighten the brake shoes enough to achieve max braking power.

Next, have you pulled the breakaway pin and tried to pull the trailer? As a "very crude and unsophisticated test" you can go to a parking lot, unplg the 7 pin connector from the tow vehicle, pull the breakaway pin and try to tow the trailer for several feet. That will apply 100% electrical power to the brakes and they should, in that test, provide the maximum capacity breaking power.

This is not a substitute for measuring voltage/amps to the brakes, but it will give you some idea whether the brakes are working because it eliminates the tow vehicle from the circuit. If the brakes do work in this "test" then you'll need to determine whether it's the trailer umbilical or the tow vehicle that is limiting your "max breaking capability"....

But, the first step, if you haven't or didn't do it, is to manually adjust the brakes so you're starting with a "functional system" not relying on the self adjusting feature to correct a "too big of an adjustment to start with".....

 

[mtruckert]

I did spoon them up manually during the install prior to the testing. But I did not try the emergency disconnect. I will try that next. I am also going to run a new cable from the terminal block to the front left brake (this is the starting point in the daisy chain for the rest of the wheel brake wiring). The 25% voltage drop along that section of wire bothers me from as an engineer...

 

[Viper02]

Since you have 12.5 volts at the trailer junction box the 7 way plug connections from truck to trailer appear to be good…

However..check the ground wire at the trailer junction box.. it’s common to all four magnets

The voltage should not be dropping that much.. IMO…

On my fifth wheel the voltage when measured at the magnets with brake pedal depressed is over 12 volts

The four magnets are all wired in parallel so what affects ONE affects ALL

I’d ohm the ground and common hot lead to the brake magnets and see what those readings are..

That’s after you do the emergency brake pull the pin test and verify the brakes all engage…

You could also measure the voltage to those magnets when emergency brake module pin is pulled … with truck not connected and it should read close to the battery source voltage

 

[JRTJH]

Just an afterthought.....

When you pull the pin on the breakaway switch, don't "dilly-dally" around too long. That switch is designed to stop the trailer in an emergency, it's not intended to carry the amp load of "playing around with the brakes for hours on end"... So, figure you need to pull the pin and do what you're going to do and get the pin back in the switch in 3 or 4 minutes. Leaving the pin pulled while you're searching the internet to see what to do next is an excellent way to melt the switch and need to buy a replacement....

Fortunately, they only cost about $7 or $8, so not an expensive lesson, but one you don't need to learn the hard way....

Pull the pin, do your checks and reinstall the pin... You'll save yourself some work that way......

 

[skids-JAY]

I am not a brake mechanic, but the brakes may need to be burnished. I had a new trailer that I was concerned about until many brake applications and then it started braking better. Also, your gain knocks down maximum voltage for brakes (right?) so that 7 would be 70% +/- I would think pulling the emergency stop pin would apply the whole amount of battery charge… Again, I don't know much about this stuff.