Smith's RV Centre

Problem

Possible Cause

Correction

Weak Brakes

Loose connections

Inadequate trailer ground
Short circuit
Incorrect variable resistor setting

Worn or defective magnets
Poor brake adjustment
Bent backing plate

Contaminated lining
Inadequate guage of wire

Stoplights connected in brake
circuit






Improper linings
Worn linings
Worn brake drums



Out-of-round drums
Loose axle on springs or frames

Loose lining on rivets
Excessive load on trailer



Using trailer brakes only

Check that all connections are
clean and tight
Check for proper grounding
Check electrical circuit
Check for proper setting to avoid
too much resistant
Replace magnets
Adjust brakes
Check backing plate flange;
correct if necessary
Check and replace
Refer to manufacturer's wiring
recommendations
Stoplights must not be connected
in the break circuit; the
graduation of the current
changes as it passes through
the controller, resulting in weak
or grabbing brakes; wire a
seperate circuit for the stoplight
switch
Replace with proper linging
Reline with new linings
Inspect the break-drum surface;
it should be free of scoring or
excessive wear; machine or
replace drums as necessary
Machine break drums
Inspect and make necessary
repairs
Replace brake shoes
Check to make sure trailer is not
underbraked; check the brakes
on each axle to make sure they
are working
Use of trailer brakes only can
cause brake fade or loss of
friction due to excessive heat

No brakes

Open circuit


Improperly wired and inoperative
controller
Poor brake adjustment
Defective variable resistor

Worn or defective magnet(s)
Short circuit
Defective connector plug




Burned-out resistor

Check for broken wires, loose
connection, improper grounding,
or faulty connector plug
Rewire controller; check
controller operation
Adjust brakes
Check for loose or broken
connections
Replace magnets
Check electrical circuit
Check plug between tow vehicle
and trailer for loose connections,
dirty or corroded blades, or
broken Bakelite insert in socket,
shorting blades or pins
Check resistor for continuity;
replace if necessary

Intermittent or surging brakes

Out-of-round drums
Inadequate trailer ground


Broken magnet lead wires

Loose wheel bearings

Turn or replace drum
Check for proper grounding
Note: A ground through the
coupler and ball is inadequate
Bench-check magnets and
replace if necessary
Check and adjust bearings

Noisy Brakes

Excessively worn lining

Weak or broken springs

Improperly located flange; bent
backing plate
Contaminated linings

Improper bearing adjustment



Incorrectly adjusted brakes
Incorrectly adjusted shoes


Grease on linings
Worn magnets

Check and replace shoes if
necessary
Check for weak or broken
springs; replace if necessary
Check and replace if necessary

Check and replace contaminated
linings
Check and adjust wheel
bearings; check for worn or
damaged bearings; replace if
necessary
Check brake adjustment
Adjust starwheel until there is a
heavy drag, then back off adjuster
slightly
Replace leaky seal and linings
Check for excessive or uneven
wear; replace if necessary

Breakaway switch fails to function

Weak or dead battery


Faulty breakaway-switch wiring




Faulty breakaway-switch





Only one brake working








Poor electrical connection

Replace with new 12-volt DC
battery; if brakes fail to function,
replace breakaway switch
Check breakaway-switch circuit
for broken or frayed wires;
replace where necessay.  Each
splice must have a good
connection
Check breakaway switch by
pulling pin and attempting to tow
trailer; if switch works, brakes will
engage.  Electrically disconnect
tow vehicle from trailer to avoid
destroying brake control
Check the amperage at each
brake; where no amperage is
indicated, check the wires
leading to the brake; if no defect
is found, remove magnet from
backing plate and check for
amperage capacity, ground, or
short; if brake is okay electrically,
check for mechanical defects
Check wiring for loose
connections, broken wires, or
worn insulation; rewire as
necessary

Grabbing or locking brakes

Improperly installed flanges

Contaminated linings

Controller too sensitive
No variable resistor







Weak or broken springs

Check flange locations; refer to
axle manufacturer
Check and replace badly
contaminated linings
Adjust brake control
A variable resistor is required
when brakes have a greater
stopping power than is
necessary for the weight on the
axle; install variable resistor
when necessary. Note: Not
required for electronic brake
control
Check for weak or broken
springs; replace is necessary

Dragging brakes

Incorrectly adjusted brakes
Insufficient gap between
hydraulic controller
Excessive residual pressure in
the tow-vehicle hydraulic system
or "gummed up" hydraulic
controller cylinder
Improperly installed flanges

Badly corroded brake assembly



Weak or broken springs

Worn or bent magnet lever arm

Check brake adjustment
Replace controller contact pins
and coil
Purge tow-vehicle hydraulic lines;
replace fluid; replace controller


Check flange location; refer to
axle manufacturer
Check break assemblies for
corrosion; be sure magnet levers
operate freely; clean and
lubricate brake assemblies
Check for weak or broken
springs; replace if necessary
Replace magnet and lever arm