45 Collectable Model Trains: Maintenance Tips: My locomotive whistle/horn doesn't work.
Description
This article is from the Model Trains FAQ, by Christopher D Coleman with numerous contributions by others.
45 Collectable Model Trains: Maintenance Tips: My locomotive whistle/horn doesn't work.
Lionel's whistles/horns use an often testy relay to trigger them.
Normal track current is AC which causes the solenoid to reverse
directions of "pull" 60 times a second causing the unit to buzz
slightly in neutral (see MOTOR DESIGN for further discussion). When
the whistle activator is pushed some current is diverted through a
rectifier and converted to DC. This DC supply superimposed on the AC
causes a constant field on the solenoid, pulling up a contact arm to
its contact. The contacts form a switch between the battery and horn
or the track and the whistle motor. Diesel horns use a vibrator
permanently enclosed in a metal casing while steam whistles use a
motor driven impeller in a resonance chamber.
to coil frame +-+ coil supply and supply to
whistle/horn
===============
|-------------| +- supply to whistle/horn
|-------------| | + coil supply
|----coil-----| | |
|-------------| | |
|-------------| | |
to coil frame =============== |__ upper contact
I__________________ lower contact arm
hinge
The whistles on Lionels are located in the tender and horns in diesels
and electrics may be in either the powered or unpowered unit. Follow
the discussion above for removing shells. FIRST if you have a diesel
or electric check the battery. Never leave a battery in a diesel for
extended periods since it can corrode and destroy your locomotive with
battery acid. Check the battery's charge.
Test the relay. One common problem is that the relay's lower contact
arm is not reaching the upper contact arm. Place the unit on the track
and try to activate it manually with a small screwdriver (you will
need track power for whistles, but not for horns). If it sounds, there
is a problem with the relay or the wiring to it and if not it is with
the horn or whistle or the wiring from the relay to the whistle or
horn. If the coil does react to the activator, but the contacts do not
reach each other, the arms may be CAREFULLY bent closer if needed, but
not too close or it will contact at every bump in the track. If there
is no response from the coil from different activators, try connecting
the supply directly to the coil supplies (not the contacts) and
throwing the activator. If this fails to activate the coil, it is
likely burned out and needs to be replaced. If it alleviates the
problem, your track pickups or wiring to the coil are at fault.
To test the whistle apply transformer leads directly to the inputs to
the motor (one may be the frame)(throwing the activator is NOT
necessary). If it runs, the whistle motor is not the problem. If on
the other hand you trace the problem to a whistle, test and repair it
just as described in the locomotive motor repair above. The same basic
motor design is used. DO NOT TRY TO OPEN THE RESONANCE CHAMBER! You
will destroy it. You may remove the motor and flush plastic ones with
water but usually not metallic ones.
To test the horn use a couple of jumper wires to connect the battery
terminals directly to the horn leads (one is a common ground with the
locomotive's frame ground). If it operates, the wiring is at fault. If
you trace it to the diesel horn, there is a small adjustment screw on
the underside of the horn with a locking nut. It adjusts the play in
the vibrator that creates the horn noise. Try various positions with
battery power applied. If you still get no response replace the horn
unit. Replacements are available.
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