The horn is a high current device. The horn switch in the
steering column is not. In order to solve this problem
a relay is used. On a TF truck, the relay is on the
engine side of the firewall, near the driver's side
hood hinge.
One terminal of the relay connects to some point in your
electrical system that is hot all the time. The second
terminal connects to the horn. The third terminal connects
to the horn button. The big question is which terminal is
which. If your lucky the relay may be marked. Something
like BAT, HORN. I'm never lucky.
If you have an volt-ohmmeter you can figure out which terminal
is which.
a. Unhook all three wires from the relay.
b. Use the ohmmeter to find the pair of terminals
that show continuity. Mark one of the pair as
terminal 1, the other as terminal 2. Mark the third
terminal (the one that had no continuity to
terminal 1 or 2) as HORN.
c. Connect terminal 1 from step b to ground.
d. Switch the ohmmeter to DC voltmeter mode.
e. Connect + lead of voltmeter to the HORN contact
on the relay.
f. Connect the - lead of the voltmeter to ground.
g. Set the voltmeter range to measure 12 volts.
h. The voltmeter should read 0v.
i. Touch a wire with 12v to terminal 2 while observing
the voltmeter. There may be a small spark. You
may hear/feel the relay pull in.
If the meter reads 12v
mark terminal 2 as BAT
mark terminal 1 as BUTTON
If the meter reads 0v
mark terminal 1 as BAT
mark terminal 2 as BUTTON
Disconnect all the temporary connections from steps a. thru i.
and wire the horn like this:
Connect BAT to the battery. Needs to be hot all the time.
Use large wire, at least 12 gauge. 10 would be better.
A good place to connect to would be the starter end
of the positive battery cable. Most FLAPS carry crimp-on
connectors with a large enough "hole" to fit over the
same stud that the battery cable connects to. If your
wiring kit has connections for horns use them instead.
Connect HORN to the terminal on the horn. Again, use
large wire.
Connect BUTTON to the wire in your steering column.
Not as much current being carried here. 16-18 gauge
wire is OK.
-----Original Message-----
From: Mike Suriano [mailto:climbandmaintain@yahoo.com]
Sent: Sunday, September 24, 2000 8:12 AM
To: oletrucks@autox.team.net
Subject: [oletrucks] Horn wiring
Can someone please explain to me how to wire the horn?
I have the complete harness (Chevy Duty) all hooked up
but for the life of me can figure out how the horn
hooks up to the steering wheel. I have the a terminal
that goes to the horn and one ending inside the cab.
I assume that I need to run a wire from there to the
horn button? How does this thing attach to the
steering wheel? I've looked over the manuals and I can
find a picture of it at all. Can someone help me out?
Thanks,
Mike
Clueless on Cape Cod
=====
1959 Chevy Apache
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oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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