John Voice wrote:
> Hi Listers
>
> The speedometer needle is jumping erratically, Do you think it could be
> the drive or is the speedometer gauge in need of servicing?
>
> Thanks in Advance
> John
> B9470748
John,
There are many things that can do this, but the very first thing to look at is
your speedometer cable. First, look at the outer sheath (under the black plastic
outer cover, and visible at the speedo connection end. If it is the original
plastic inner tube, then you should replace it with the newer spiral steel
cored
cable. Readily available, including new core cable, form Sunbeam Specialties.
The outer cable guide (inner tube) can wear quickly, if plastic.
If it is steel core, already, you may have an inner cable that has become
defective. It usually breaks one of the many strands, which rub the inner
sheath
and catch and let go, making the speedo needle jump.
Replacement is cheap with a heavy duty core. Any speedo shop can do this, but
some don't realize it. They believe you have a standard British speedometer,
which uses different inner cable end forming, or other hardware. Tell them that
the TIGER (not the Alpine) is stock Ford on both ends, (and insist you are
correct, even if they think you're nuts) and they can just pull out the old
cable,
make a length, end fittings like original, using HD cable, grease it well, and
shove it back in. Fairly cheap. Maybe $9.00.
Make sure the outer end sheath is not loose on the outer cable. It is swaged
on,
and sometimes gets loose. It can be re-swaged to tight fit, but make sure it
ends
up the same length by re-swaging in the same location. I screwed this up and
ended up with a non-standard length inner cable. No great harm, just need to
use
the old one if I have to make another.
If non of the above are the cause, you are probably looking at a
re-magnetization
of the speedometer needle drive couplings. The process is not expensive, but
the
speedo needs to be removed and dismantled. The cost is barely different than a
rebuild and calibration of the odometer (gear replacement, vs magnetization and
return spring adjustment). In this case, you need a qualified repair place like
MOMO, Nissonger, West Valley Speedo (Los Angeles), or there is a place in the
Northern California Bay area they go to. In any event., you need to do some
homework before you send it to them.
One recommended method of giving them the data they need to adjust for your tire
size, is to place two chalk marks 52.8 feet (52 feet, 9 3/4 inches, approx.)
apart on flat, level, no traffic street. Put the front (or rear) tire center
ground contact next to first mark. Make sure your tires are correctly
pressurized. Disconnect speedo cable from instrument, and let it hang down into
the driver's compartment until you can see the nut and cable end. Put a 'flag'
of
masking tape around the inner core, so you can see the 'flag' sticking out.
Note
the position of the 'flag'. Have a friend, or two, push your car slowly until
you
reach the other chalk mark at the center of the tire. No need to mark the tire,
or count the tire revolutions. Count the core revolutions! Repeat this a
number
of times until you feel you have a good average for the number of turns, and
fractions of a turn, the cable makes over this distance.
If you supply this number (and your 52.8 foot reference distance) to any of the
named sources, they will re-build your speedo so that the odometer, trip meter,
and speed needle are correct. The needle may only be exact around 55-75 mph,
because this is the most important area. It can be made exactly correct in any
small range, put the instrument is just not good enough to be accurate over it's
whole face, and that's just the way it is. It will be close enough, anyway, at
the
other speeds. This will probably cost you about $125, and hope that any new
gears
you need are available. It will be less if they just make your speedometer
needle
accurate, and leave the odometer, trip meter gears alone. They will not be
correct, but you will know exactly how much to correct it for the exact
distances
after they finish. This is OK for street driving, and gas mileage, but
difficult
for rallies, as you need to keep correcting the readings. It's only a
multiplication of the reading by a constant number, but it is another step for
your navigator. If you bring a lap-top and a spread sheet, it will do it
automatically, if programmed correctly.
Hope this helps. There is a method of pushing your car over this distance, and
measuring the number of tire revolutions, but this requires a knowledge of your
rear end ratio, and the gears in your transmission and cable drive. The
instructions given take all that into account, without knowing what they are, or
needing to.
Good Luck,
Steve
I
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Steve
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