New gauges (2)

Well, the problem of fitting the rev counter in the Morris is more difficult than it on first sight seems to be. With the help of the MM forum UK and sone search on the internet I now know how to connect. The + connector should be connected to earth and the -12 to +12V. The clearest picture shown here below (Smiths version):

The next problem is a missing part: The small block with the slug of the white wire. 

As explained here: http://www.uniquecarsandparts.com.au/how_it_works_tachometer.htm: 

One of our favourites is the Smith's Industries version as fitted to the E-Type Jaguar. This is a good example of the impulse tachometer. Two pairs of connections were required, one pair for the supply leads and the other for the pulse pick-up leads. The pulse leads were, in fact, one continuous wire with a loop (forming the primary winding of a transformer) taken around a soft iron core projecting from the rear of the tachometer casing. The advantages of this type of signal pick-up were that there was no break in the ignition wiring, so a break in the tachometer circuit would not affect the ignition; and that there is no direct electrical connection to the ignition from the tachometer circuit.

Back to the forum to see if a example of this 'soft iron core' can be used to make one my own.

One more remark on the Mini forum: 

The figure above is helpful if you are fitting a Smiths RVI type tachometer to a car with a points-type distributor. (RVI will be somewhere on the gauge face). If your car has electronic ignition, do not bother trying to fit an RVI tach to it. Chances are very strong that the tach will not work correctly.

A better choice is to find a Smiths RVC type tachometer as was used on later MGBs and Midgets. As above, RVC will appear on the gauge face. The RVC tachs are a more modern design AND they will work with either points or electronic ignitions. Unlike the figure above, an RVC tach connects to the ignition system using a single wire connected to the coil (-) terminal. Of course, it still needs power, earth, and illumination connections.


And of course ... I have a RVI type. Hopefully, we can solve that problem too. Might need the help of an electronic expert.

To be continued....