BY JAMES BERRY I PHOTOGRAPHY BY THE AUTHOR
Technically Speaking
here is a tendency to
immediately blame the
relay when there is any
failure in a component.
However, we learned last
month that the most common cause of
a horn failure on a Corvette is due to a
ground circuit failure.
The most common failure is that ground
is not supplied through the rag joint. If the
ground is being supplied through the rag
joint, there are a few other components
that can be problematic in the ground
circuit.
Remember, all the horn button does is
supply ground to the relay. A simple test
to confirm a ground problem is to use a
jumper wire attached to a battery ground.
Then ground the relay where the ground is
supplied from the horn button. If the horn
blows this will confirm you have a ground
problem. On different year Corvettes this
wire can be in different locations at the
horn relay, be sure to look at a wiring dia-
gram for your specific year model.
If there is a problem in the ground cir-
cuit, there are a few other things to check
in the ground circuit.
The horn button contact retainer is
susceptible to corrosion. If this happens,
sometimes the horn will blow if you
push the button in a specific position. For
example, it may blow in the 11:00 o’clock
position, but not in any other. This contact
must be clocked in the correct position to
make contact with the horn contact brush
connector.
The horn contact brush connector is the
plunger part that fits under the horn con-
tact and is activated by the horn contact.
This has a plastic keeper, which I have seen
broken in many Corvettes.
On some Corvettes there is a black
ground wire that runs from the body of
the relay to a screw that attaches the horn
relay to the radiator support. Make sure
this ground has a paint-free surface and ismaking a good connection at the radiator
support.
Now for the horn relay. When the relay is
closed, battery voltage is normally supplied
to the horns through the green wire. If you
have tested the horns as described in Part 1
and you think you may be having a horn
relay problem, first check to see if you have
battery voltage at the horn relay. No mat-
ter what system or what model of car I am
working on I always check for voltage with
the key on.
Some horn relays have a fusible link
wire located near the relay. If 12 volts is not
being supplied to the horn relay and you
have checked the fuse in the fuse box, be
sure to check the fusible link wire.
If you think the horn relay has failed
internally you can simply replace it or try
and repair it by removing the relay. Be sure
to isolate the power wire so it won’t short
or arc against anything metal.
Use a pair of small needle-nose pliers
or a flat-blade screwdriver to open the
crimped areas where the relay housingcover is attached to the relay. Carefully
remove the cover.
The horn relay contacts can build up
corrosion over time. You can use a points
file or fingernail file to remove the corro-
sion off of the points. File the corrosion off
but do not file the points themselves too
far down.
If the corrosion is not too bad, you can
clean the relay with some low pressure
compressed air.
If there is heavy corrosion in the relay I
like to use WD-40 with a wet piece of solid,
glossy paper and fit it between the closed
contacts and the corroded areas of the
relay. Do not soak the relay in any cleaner.
Be sure to do a final cleaning with
100-percent pure alcohol and dry with
clean air.
If you want to keep your original relay
and the above did not repair the relay you
will probably need to send your original
unit out to an expert for repair or you could
replace the internal mechanism with a
new one.C2 & C3 Horn Button Repair, Part 2
T
12 VETTE 19.