Canít warn those pesky SUV's to stay away from your beloved MGB?
Your problem could be in the steering column contacts. Mine was.
If you havenít had your columnís plastic surround pieces off
then you may be able to repair your non-working or intermittent horn
without a lot of trouble.
for the later year chrome bumper B's from about 1970 and up but the
technique should be the same for other years.
toots feebly or sporadically when you press the horn button then more than
likely itís a horn button - horn brush contact problem.
works by grounding a purple/black wire at the steering wheel. The
purple/blackís 12vdc is carried through the harness to a brass spring
finger contact inside the plastic column surround pieces. This finger
contact rides on a brass ring on the back of the steering wheel hub so it
can make continuous contact when the steering wheel is turning. The horn
brush pencil mounts in a hole in the hub and touches the other side of the
brass ring on one end and the horn button on the other. When you press the
horn button it grounds the horn brush pencil and toots the horn. Itís
pretty simple, really.
problem is that the horn brush pencil makes contact on the brass ring in
the same place for ever how many years your car is old. Mine is a '73, so
thatís 30 years. After that many years it starts corroding and arcing
and burns a nice little carbon dot on the brass ring. Plus, on the other
side of the brass ring that makes contact with the brass finger, the area
where the finger (that brings the purple/black wire into contact) makes
contact gets corroded over the years. It all adds up.
pull off the horn button. You can then see the horn brush pencil sticking
up out of the hub. Take your voltmeter ( you do have a voltmeter donít
you?) and test the brass end of the pencil to see if you have 12vdc.
you do, then rotate the steering wheel to several different positions and
re-test. If you lose the 12vdc then proceed. If you donít then the
problem may be in the horn button itself, another easy fix. Weíre going
to assume you donít have the 12vdc. Grab the horn brush pencil and pull
it out of the hub paying attention to which end goes into the hub. Test it
with your ohmmeter to make sure itís got good continuity and the wire
inside isnít broken.
steering wheel off. You can do this by loosening the nut on the steering
shaft and rocking the wheel
back and forth while you pull out. Leave the nut on until you get the hub
worked loose from the steering shaft. You may have to pound the end of the
shaft with a rubber hammer while pulling upwards on the wheel. If you
donít leave the nut on, the wheel will suddenly come loose and whack you
silly. When you regain consciousness, we can proceed
you have the steering wheel/hub off turn it over so you can see the brass
ring on the bottom we were talking about.
down inside the plastic column surround and you can see the brass spring
finger contact that rides on the brass ring. It should all make sense now
that you can see it. Test the brass spring finger for 12vdc. If itís
there, then proceed. If not, you have purple/black wire problems.
case, now that you have the wheel off you might as well take care of these
contacts, since youíve done the hard part.
wheel right side up and look inside. Youíll see two Phillips (Pozi-Drive) screws that secure the brass ringís plastic holder.
them out and the brass ring holder assembly will come right off.
clearly see the spot at the top where the horn brush makes contact. It is
corroded and cruddy and the poor contact has caused heating. You can see
where the plastic has slightly melted.
three tabs up with a small screwdriver. You may want to use a set of
needle nose pliers to bend them the rest of the way. You only need to get
them up enough to pop the brass ring out. Theyíre pretty stiff and seem
easy to work with.
brass ring pops out hereís what you have. The burnt spot is evident.
fine (800-1000 grit) sandpaper or your Dremel tool with a wire brush and
clean an area between two of the tabs. You're going to rotate the brass ring
so you donít use the burnt area so just clean up another area about
midway between two tabs and towards the outside of the ring. Turn the ring
over and clean the other side. The finger will be riding around the entire
circumference of that side. Smear a little dialectic grease on the ring
if you have any. Pop the ring back on the holder making sure you turned it
so the new spot is under the brush pencil hole.
tabs back over with the small slotted screwdriver, and youíre back in
business. Put the plastic holder back on the hub, making sure that the
brush pencil hole in the holder lines up with the hole in the hub. The
hole is at the bottom of this picture.
the wheel/hub back on the steering column and put the brush pencil back
in. Test it for 12vdc. If you had 12vdc at the finger in the column you
should now have it at the end of the brush pencil.
the horn button back on, making sure to line up the hole in the buttonís
back plate with the brush pencil. The hole has a thin brass plate in the
bottom thatís easy to see. The horn will toot when you are putting the
button back on. Test the horn by tooting it a number of times, or until
you better half comes out to see what Ďtells going on. Then you can act
like you did something really complex.
ďYah, had to tear it down and
refurbish it so the horn would work, you know us MG folks - ĎSafety