BL

EE

R

G

Battery
Charge

BLA
CK

Clearance &
Tail Lights

WH
ITE

7-Circuit Receptacle

Stop &
RH Turn
Auxiliary

View Looking into Tow Vehicle Receptacle

-10-

Your trailer brakes are designed to work in synchronization with your tow vehicle
brakes. Never use your tow vehicle or trailer brakes alone to stop the combined
load.
Your brake controller must be set up according to the manufacturer’s
recommendations to ensure proper synchronization between the tow vehicle and
the trailer. Additionally, you may have to make small adjustments occasionally to
accommodate changing loads and driving conditions.
Proper synchronization of tow vehicle to trailer braking can only be
accomplished by road testing. Brake lockup, grabbiness, or harshness is quite
often due to the lack of synchronization between the tow vehicle and the trailer
being towed, too high of a threshold voltage (over 2 volts), or under adjusted
brakes.
Before any synchronization adjustments are made, your trailer brakes should
be burnished-in by applying the brakes 20-30 times with approximately a 20
m.p.h. decrease in speed, e.g. 40 m.p.h. to 20 m.p.h. Allow ample time for
brakes to cool between application. This allows the brake shoes and magnets to
slightly “wear-in” to the drum surfaces.

Trailer Wire Size Chart
Number
of Brakes
2
4
4
6
6

Hitch-to-Axle Distance
in Feet
Under 30
30-50
Under 30
30-50

-11-

Recommended
Minimum Hookup Wire
Size (Copper)
12 AWG
12 AWG
10 AWG
10 AWG
8 AWG

Braking Systems - Electric

How to Use Your Electric Brakes Properly

Synchronizing Your Trailer Brakes
To ensure safe brake performance and synchronization, read the brake controller
manufacturer’s instructions completely before attempting any synchronization
procedure.

!

CAUTION

Before road testing, make sure the area is clear of vehicular and
pedestrian traffic. Failure to brake safely could result in an accident
and personal injury to yourself and/or others.
Make several hard stops from 20 m.p.h. on a dry paved road free of sand
and gravel. If the trailer brakes lock and slide, decrease the gain setting on
the controller. If they do not slide, slightly increase the gain setting. Adjust the
controller just to the point of impending brake lockup and wheel skid.

Braking Systems - Electric

Note: Not all trailer brakes are capable of wheel lockup. Loading conditions,
brake type, wheel and tire size can all affect whether a brake can lock. It is not
generally considered desirable to lock up the brakes and slide the tires. This
can cause unwanted flat spotting of the tires and could also result in a loss of
control.
If the controller is applying the trailer brakes before the tow vehicle brakes, then
the controller adjustments should be made so the trailer brakes come on in
synchronization with the tow vehicle brakes. For proper braking performance,
it is recommended that the controller be adjusted to allow the trailer brakes
to come on just slightly ahead of the tow vehicle brakes. When proper
synchronization is achieved there will be no sensation of the trailer “jerking” or
“pushing” the tow vehicle during braking.

-12-

Brake Adjustment
Dexter electric brakes that have a self adjusting feature require no manual
adjustment. Brakes not equipped with this feature can be adjusted by using the
following procedure:
Brakes should be adjusted (1) after the first 200 miles of operation when the
brake shoes and drums have “seated,” (2) at 3,000 mile intervals, (3) or as
use and performance requires. The brakes should be adjusted in the following
manner:
1. Jack up trailer and secure on adequate capacity jack stands. Follow
trailer manufacturer’s recommendations for lifting and supporting the
unit. Make sure the wheel and drum rotates freely.

!

CAUTION

Do not lift or support the trailer on any part of the axle or suspension
system. Never go under any trailer unless it is properly supported on
jack stands which have been rated for the load. Improperly supported
vehicles can fall unexpectedly and cause serious injury or death.
2. If equipped, remove the adjusting hole cover, if present, from the
adjusting slot on the bottom of the brake backing plate.
3. With a screwdriver or standard adjusting tool, rotate the star wheel of the
adjuster assembly to expand the brake shoes. Adjust the brake shoes
out until the pressure of the linings against the drum makes the wheel
very difficult to turn.
Note: For drop spindle axles, a modified adjusting tool may be
necessary.
4. Then rotate the star wheel in the opposite direction until the wheel turns
freely with a slight lining drag.
5. Replace the adjusting hole cover, if available, and lower the wheel to the
ground.
6. Repeat the above procedure on all brakes. For best results, the brakes
should all be set at the same clearance.

-13-

Braking Systems - Electric

General Maintenance - Electric Brakes

Brake Cleaning and Inspection
Your trailer brakes must be inspected and serviced immediately if a loss of
performance is indicated. With normal use, servicing at one year intervals
is usually adequate. With increased usage, this work should be done more
frequently as required. Magnets and shoes must be changed when they become
excessively worn or scored, a condition which can reduce vehicle braking.
Clean the backing plate, magnet arm, magnet, and brake shoes. Make certain
that all the parts removed are replaced in the same brake and drum assembly.
Inspect for any loose or worn parts, stretched or deformed springs and replace
as necessary.

!

CAUTION

Braking Systems - Electric

POTENTIAL ASBESTOS DUST HAZARD!
Some older brake linings may contain asbestos dust, which has been
linked to serious or fatal illnesses. Certain precautions need to be
taken when servicing brakes:
1. Avoid creating or breathing dust.
2. Avoid machining, filing or grinding the brake linings.
3. Do not use compressed air or dry brushing for cleaning (dust can
be removed with a damp brush).

Brake Lubrication
Before reassembling, apply a light film of grease or anti-seize compound on
the brake anchor pin, the actuating arm bushing and pin, and the areas on the
backing plate that are in contact with the brake shoes and magnet lever arm.
Apply a light film of grease on the actuating block mounted on the actuating
arm.

CAUTION
Do not get grease or oil on the brake linings, drums or magnets.

-14-

Your electric brakes are equipped with high quality electromagnets that are
designed to provide the proper input force and friction characteristics. Your
magnets should be inspected and replaced if worn unevenly or abnormally. As
indicated below, a straightedge should be used to check magnet condition. For
best results, the magnet should be flat.
Even if wear is normal as indicated by your straightedge, the magnets should be
replaced if any part of the magnet coil has become visible through the friction
material facing of the magnet. It is also recommended that the drum armature
surface be refaced when replacing magnets (see section on Brake Drum
Inspection). Magnets should also be replaced in pairs - both sides of an axle.
Use only genuine Dexter replacement parts when replacing your magnets.

Straight Edge

Gaps show ABNORMAL
WEAR (replace magnet)

NORMAL WEAR

-15-

Braking Systems - Electric

Magnets

Shoes and Linings
A simple visual inspection of your brake linings will tell if they are usable.
Replacement is necessary if the lining is worn to 1/16" or less. Shoes
contaminated with grease or oil,
or abnormally scored or gouged
should also be replaced. Hairline
heat cracks are normal in bonded
linings and should not be cause
for concern. When replacement is
necessary, it is important to replace
both shoes on each brake and both
brakes of the same axle. This will
help retain the “balance” of your
brakes.

Acceptable
Hairline Cracks

Braking Systems - Electric

!

CAUTION

POTENTIAL ASBESTOS DUST HAZARD!
Some older brake linings may contain asbestos dust, which has been
linked to serious or fatal illnesses. Certain precautions need to be
taken when servicing brakes:
1. Avoid creating or breathing dust.
2. Avoid machining, filing or grinding the brake linings.
3. Do not use compressed air or dry brushing for cleaning (dust can
be removed with a damp brush).
After replacement of brake shoes and linings, the brakes must be re-burnished
to seat in the new components. This should be done by applying the brakes 20
to 30 times from an initial speed of 40 m.p.h., slowing the vehicle to 20 m.p.h.
Allow ample time for brakes to cool between applications. This procedure allows
the brake shoes to seat in to the drum surface.

-16-

Proper brake function is critical to the safe operation of any vehicle. If problems
are encountered with your trailer braking system, the following guide can be
used to find the causes and remedies for some of the more common problems.
If you are unsure or unable to resolve the problem, please contact your nearest
repair facility for professional assistance.

Troubleshooting
Most electric brake malfunctions that cannot be corrected by either brake
adjustments or synchronization adjustments, can generally be traced to
electrical system failure. Voltmeters and ammeters are essential tools for proper
troubleshooting of electric brakes.
Mechanical causes are ordinarily obvious, i.e. bent or broken parts, worn out
linings or magnets, seized lever arms or shoes, scored drums, loose parts, etc.
Replace defective parts with genuine Dexter replacements.
Please consult the following troubleshooting charts to determine the causes and
solutions for common problems found in trailer braking systems.

!

CAUTION

Best braking performance is achieved with a controller setting that is
just short of wheel lock up or slide. Overly aggressive braking which
results in wheel lock up and sliding, can cause a dangerous loss of
control and result in personal injury or death.

-17-

Braking Systems - Electric

Introduction to Troubleshooting

Troubleshooting
SYMPTOM

No Brakes

CAUSES

REMEDIES

Open Circuits

Find & Correct

Severe
Underadjustment

Adjust Brakes

Faulty Controller

Test & Correct

Short Circuits

Find & Correct

Grease or Oil on
Magnets or Linings

Clean or Replace

Corroded Connections

Clean & Correct
Cause of Corrosion

Worn Linings
or Magnets

Replace

Scored or Grooved
Brake Drums

Machine or Replace

Improper
Synchronization

Correct

Underadjustment

Adjust Brakes

Glazed Linings

Reburnish or Replace

Overloaded Trailer

Correct

Underadjustment

Adjust

Improper
Synchronization

Correct

Faulty Controller

Test & Correct

Loose, Bent or Broken
Brake Components

Replace Components

Out-of-Round
Brake Drums

Machine or Replace

Insufficient Wheel Load

Adjust System Resistor
and Synchronize

Faulty Controller

Test & Correct

Broken Wires

Repair or Replace

Loose Connections

Find & Repair

Faulty Ground

Find & Repair

Braking Systems - Electric

Weak Brakes

Locking Brakes

Intermittent Brakes

-18-

SYMPTOM

Brakes Pull to
One Side

CAUSES

REMEDIES

Wrong Magnet
Lead Wire Color

Correct

Incorrect Adjustment

Adjust

Grease or Oil on
Linings or Magnets

Clean or Replace

Broken Wires

Find & Repair

Bad Connections

Find & Repair

Underadjustment

Adjust

Improper
Synchronization

Correct

Improper Controller

Change

Faulty Controller

Test & Correct

Harsh Brakes

Underadjustment

Adjust

Lack of Lubrication

Lubricate

Noisy Brake
Broken
Brake Components

Surging Brakes

Dragging Brakes

Replace Component

Incorrect Brake
Components

Correct

Grease or Oil on
Linings or Magnet

Clean or Replace

Out-of-Round or
Cracked Brake Drums

Machine or Replace

Faulty Controller

Test & Correct

Overadjustment

Readjust

Out-of-Round
Brake Drums

Machine or Replace

Incorrect Brake
Components

Replace

Loose, Bent or Broken
Brake Components

Replace

Faulty Breakaway
Switch

Repair or Replace

Loose Wheel
Bearing Adjustment

Adjust

Bent Spindle

Replace Axle

-19-

Braking Systems - Electric

Troubleshooting

How to Measure Voltage
System voltage is measured at the magnets by connecting the voltmeter to the
two magnet lead wires at any brake. This may be accomplished by using a pin
probe inserted through the insulation of the wires. The engine of the towing
vehicle should be running when checking the voltage so that a low battery will
not affect the readings.
Voltage in the system should