by George Dow April 2017
While churning over my 1985/6 +8 on the starter motor after a period of
lay up I noticed the (electronic) rev counter took a pulse that caused
the needle to deflect up the scale and drop back to sit at 2500RPM!
The engine had not fired up at the time.
When the engine did fire up the needle rose from 2500 RPM with the rise
in engine revs, thus was responding to changes in revs though giving a
new and false higher reading. On switching the ignition off the needle
dropped to zero and when the ignition was switched back on with the
engine now stopped, the rev counter needle returned to 2500 RPM! At
any time thereafter as soon as the ignition was switched ON the rev
counter needle would rise immediately to read 2500RPM. If the starter
was engaged and the engine fired up the needle would rise from
At the time I did not want to take the instrument apart in the off
chance I might damage it beyond possible repair, and did not want to
send it off for repair lest it get lost in the post or any similar issue
that may leave me with a hole in the dashboard. Thus it seemed wise to
try to buy a replacement, which when I contacted a Morgan specific
dealer, I was told that my year of +8`s instrument was no longer
available as new though could offer a repair service... SO back to possible
|SpeedyCables is a division of Caerbont Automotive Instruments Ltd (CAI), an independent company in
South Wales engaged in the design and manufacture of car
instruments, instrument clusters, senders, electronic control and
interface modules and wiring harnesses for the specialist automotive and
They are an important supplier to Morgan and other noted automobile and
marine manufacturers. They supply the Smiths lineup as well.
On searching the web I came across a Welsh company by the name of Speedy Cables. After further
search on their service, and found there were a few complaints as to the
lack of speed in their business practic. However, found them to be
speedy enough they answered my email in four days (Fri-Mon) and I took
delivery of my replacement newTachometer on the following Friday.
Speedy Cables listed a chrome rimmed Tachometer in the size and
with a very similar face to that of my tachometer. Hopwever,
their return email assured me they could fit a matte black rim similar
to my originalt. Job done £134.84 +vat and
postage. Well...er... not quite job done.
Read on. NOTE When ordering, you should note to Speedy what color your internal illumination is..
While I was delighted to find a new replacement that looked identical
other than a few words of small print along the bottom edge of my
original instrument identifying it as being an 8CYL and line of text
denoting its country of origin, etc. none of which mattered a jot to
me. The new instrument itself is a more up to date design than the
original and requires it to be setup in order to operate correctly
as well as care taken in connecting it up to the Morgan`s electrical
system, lest you damage the instrument's internals.
But there is nothing difficult in the processes required if you can crimp a few
terminals to make connection between the old and new.
SETUP PROCEDURE: READ THEIR INSTRUCTIONS.
... the tables printed
therein seem far more complex at first glance than they turn out
The new tachometer is a negative earth/ground device as was the old one
so no issue there though it`s internal circuitry is different and
many digital electronic devices has to be set-up to give the appropriate
relative to the INPUT
it receives, given this new instrument is
capable of taking input from any one of a multitude of electrical
devices to give a read out in RPM.
From the images, it can be seen that there are physical differences
though none that matter relative to the way it looks when in place in
the dash. On the rear of the instrument there is a round black rubber
grommet which provides access to the little light-bulb
holder for instrument illumination (more on that later). More
importantly it provides access to a tiny series of eight "dip" switches
contained in a block which must be individually switched into a specific position (either ON or OFF) to
match the car's input to the instrument. It sounds complex but is not, all
that is required is something the size of a tooth pic or very small
screwdriver to flip the switches to their required position.
The image of the dip switches (left) will hopefully help simplify
understanding. ON is also marked
on the left hand side of the block
in order that a switch can be
clearly seen to be switched to either off or on regardless of the angle
such a block may be mounted on a circuit board.
My 8-cylinder fires 4 times for each revolution of the crank so, from
the provided tables, I placed the switches as instructed which, in
my case, was a simple operation requiring only two of the switch
positions to be altered from the way they were set when I received the
instrumen. Switch 1 and switch 2 arrived in the ON position which was correct
for a 4 cylinder
input. Also switch 8 was ON, which seems to be a requirement
for the majority of inputs, as it is in the case of both 4 and 8
cylinder engines. The chnages required to switch the instrumnets from a
4 to a 8 cylinder engine was merely to switch # 2 to OFF and
switch # 3 to ON.
Only after the dip switches have been set should you think about
connecting the instrument to the vehicles wiring and only then
(according to the instructions) with the NEGATIVE strap disconnected
from the battery.
To wire it in, you can either cut off the existing Lucar/spade terminals and replace
them with your choice of straight through connectors. Or you can solder the
connections, or as I did, you can make off the ends of the wired plug supplied
with the instrument with crimp on MALE Lucar connectors that will then
plug into the existing connections. Of course you need to take care as
the number and colours of wires supplied with the new instrument do not
exactly match those used in the existing installation, though the
instructions contain the necessary connections information.
CONNECTIONS - 4
There are four connections (though the pre wired plug has
, two of which are unnecessary. I just bent the unneded two round and tucked the ends into the
sleeving around the plug wiring.
Illumination: The internal illumination of the instrument is supplied, as the original
was, with the RED wire the WHITE tracer.
Signal from the Coil: This signal is normally fed through the WHITE wire the BLACK tracer. You can see it attached at its other end to the coil.
However, it seems the
preference here (from the Carerbont instructions) is to use the RED/BLUE in the plug
wiring for the signal, which I did. WEBMASTER NOTE: Beware here. On EFI cars the same white wire with a black tracer feeds the tachometer and then on
from the tachometer to the ECU, giving it a vital signal. Without this
wire connected to the ECU, the car will not start or run.
The green in the wiring loom can be connected to the green in the plug
wiring and supplies the power to the instrument when the ignition is
switched on. Please note the instructions suggest that the green
supply wire should be fused at 3 Amps, apparently to protect the device
electronics from any power more than that. I considered
it advisable to fit an in line accessory fuse (image on the left)
between the green of the Morgan`s wiring (excuse my red wires for the
fuse holder) and that of the tach's plug. Use a 3 amp fuse. Fuse
holders can come with any fuse type you wish. Match the fuse with the type your car already uses.
fuses also come with Lucar connectors already crimped in place, one male
and one female as in the image, though be sure to have no bare metal
showing when the connection is made.
.. There are female connectors that have insulating sleeves over them. WEBMASTER:
In such spots, where future access is a bit of a pain, I now use blade
fuses in self-diagnosing holders. They only cost a 1-2£
more and allow trouble checking at a glance.
The last wire to connect is the earth/ground which for both the instrument
and the Morgan`s wiring loom is BLACK so no complication there. NOTE
case of the instrument does not require earthing as the illumination
circuit is now internal to the instrument thus the original bulb and
holder are no longer required though the red/white from the existing
bulb is used as above to supply the feed to the light in the new
: One other little issue which may be of no consequence to some is that
the original instrument was illuminated in green, whereas the
replacement is lit in white.
On contacting SpeedyCables again, they supplied me with a replacement lamp holder
with an integral green LED (Light Emitting Diode) unlike the filament
lamp originally supplied. With the replacement LED fitted the new Tachometer
matched now my Speedometer`s colour when the lights were switched on...
NOTE: It is IMPORTANT to remember that LED`s are polarity dependant thus if
the LED does not light up after fitting it is best to remove it and
replace it in the hole 180 degrees round from your first attempt and in
doing so you will have reversed the polarity of the connections to the
In my case all worked well enough though on checking with my
timing light the gauge seemed to be reading perhaps 50RPM over though
whether that was down to the timing light read out innacuracy or not..?
As I am not racing My Morgan to it`s limits and a.. POSSIBLE.. 50RPM
discrepancy is not a big deal for me.... if it exists at all.
THE ORIGINAL UNIT:
Now that I have a working Tachometer I had the confidence to open up my
faulty instrument though found nothing obvious within, and while I had
it opened I took the opportunity to photograph the internals in the hope
that those with the skills and access to electronic components might
On a far more basic level, from the image of the internals
original instrument you may notice the use of translucent green plastic
as part of it`s internal framework, as part of that framework also
provides the means of holding the original lamp holder to the rear of
the instrument and in doing so filters the instrument illumination to
provide the green illumination that was seen as white until the green
LED was fitted.
Should you have occasion to strip an original instrument I would suggest
that you remove the two Philips/cross head screws on the back of the
case...No need to remove those recessed in the green plastic also
visible on the rear of the case. Remove the two small nuts at the base
of the long threaded screws that are used to hold the instrument to the
rear of the dashboard. there are two tiny nylon washers under those nuts
which should also be removed as they grip the threads tightly and would
restrict removal of the instrument internals. Once the fixings have
been removed it seems wise to then turn your attention to prising up the
tabs holding the rim to instrument case. I found these to be quite
resistant to bending though used a small sharp screwdriver
successfully. Note that the tabs do not need to be bent till they are
straight as there is enough flexibility in the rim to enable the tabs to
be eased over the edge of the instrument case individually.
Try not to touch the face or the inside
of the glass.
The face of the instrument is somewhat recessed so the whole device can be placed
face down on a clean stable area in a bid to apply pressure to remove
the internal structure as one piece, which in the case of my instrument
was not as simple as expected. There is a foam backing fixed to the rear
of the green plastic internal framework and in the case of my instrument
this had adhered to the bottom of the instrument casing. It would be
easy to damage the long threads of the screws while applying pressure to
them though if you screw the large alloy thumb screws flush with the
tops of the threads then that will provide a larger area on which to
apply pressure, I also applied pressure to the green plastic area at the
connections and working between those areas finally encouraged enough loosemovement in
the internal structure to the extent it could then be removed.