This week I finally finished installing the
instruments. The last one to connect was the tachometer.
This is a Smiths RVI 2401/00B. The “I” stands for
Impulse, which means it is electrical and non-mechanical (no tachometer cable
to the engine). The back side shows a loop of white wire, or impulse loop. One
side of the wire is marked red, and the other side is marked black.
Since Old Biddy is a positive ground car, the red
wire connects to the coil, and the black usually connects to the distributor
(reverse that for a negative ground car). Notice I said “usually”. I wanted to
connect it up as it would have been done if built in the factory, such as the way an MG Midget was hooked
up. So I traced the white coil wire with my continuity meter from the coil to
the fuse box and marked it with a red Sharpie.
Then I traced the wire from the ignition switch to
the fuse box, and marked it black. This is the wire that would have been
connected to the distributor. In essence, the white wires go through the
tachometer instead of the fuse box, like a Midget and MGB. I connected the
wires so I could cut them to length inside the car.
I set the tachometer in its place in the panel and
hooked up the wires inside the car while disconnecting the other ends back at the fuse box. I
went to turn the panel lights on to test the tachometer light and it did not go
on. Good thing I did that while the white wires were not connected because I found that the tachometer was not grounded.
I ended up connecting a black wire to ground.
Then, I flipped the switches again and all the panel
lights went on!! Quite exciting! (Of course they are much brighter in real life.)
Next step is to connect the white wires at the
fuse box to the tachometer and test it. But…cantankerous Old Biddy will not
start. I have to wait for this weekend when the weather is supposed to get
above 50’F before I can troubleshoot. Hopefully it is only a minor setback.
Thanks for visiting.
Toddy
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