New gauges (3)

I got the tacho working. Found the small plastic part with the metal surrounding in the package that was send to me :). Only the small nut was missing. And there I think it went wrong again.

First it didn't work, everything connected as in the documents. The wire in the loop should generate a magnetic field that is used inside of the gauge to 'count'. But I replaced the missing nut with a small iron 'knob' I had (the size of the thread is imperial and extremely small). Only after changing it to a copper nut it worked! Probably the iron nut was influencing the magnetic field in such a way it could be picked up in the gauge.

So fitted it, and it looks nice I think:

With the small screw on the back I calibrated at 1000 rpm with a external rev counter.

Now only the temperature gauge is not yet working. The sensor that I have did not fit into the block, so bought a standard Mini (assuming the set has been used in a Mini). But no... The gauge gave a very cold 40C even when the engine was hot. The temperature sender is a NTC type (Negative Temperature Coefficient): Higher temp gives lower resistance. But for my gauge the range the sender gave is too high. Tested 2 versions (GTR101, GTR104) in the kitchen:

The results (vertical: resistance, horizontal: temperature):

My gauge wants 17 Ohm at 80 C....
The Smiths TT4800 should be the right one according to experienced club members. Seen them for $69 on ebay :(
That is not going to happen!

To be continued....