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MG MGA - Tacho wiring

I have an MGB tach, negative ground, to install in my MGA.
Am I right in wiring this way?
white induction wire pair in series with the ignition primary
Live from ign switch to the spade terminal at the back
Grounding through dashboard or wire it to ground?
Art Pearse

The Smiths tacho's with a face similar to the MGA Jaeger instruments were originally positive ground. To use with negative ground requires conversion of the instrument.

The white wire induction loop does go in-line between ignition switch and ignition coil, but it should not include the fuel pump or anything else in the circuit. Originally a white wire goes from ignition switch to fuse box, and you can leave that one as original. Disconnect the coil supply wire from the fuse box (leaving the fuel pump wire connected).

Run a new white wire from ignition switch to tach, and split it at the power input terminal. Continue with white wire through the induction loop, then on to connect to the coil supply wire near the fuse box (without connecting to the fuse box). End result is white wire from ignition switch through induction loop on on to the coil. If the tack doesn't work you may have to reverse direction of the induction loop.
Barney Gaylord

Thanks Barney. The Tach has already been converted to -ve ground, and used in an A previously. I will take care to separate the fuel pump.

Art Pearse

This thread was discussed between 05/09/2013 and 06/09/2013

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.