Mercury smartcraft tacho

[TwoBob]

The digital display on my smartcraft engine monitor/tacho is showing no signs of life. Absolutely dead - not a flicker of life! Stripping things back it would appear that the positive connectors in the plns of it's supply harness are corroded away to nearly nothing, but it is possible to get a voltage reading from the red and black wires in the plug that goes into the display unit. I have ordered new pins to fix the harness but have a couple of questions

1 - is it possible to test the display unit just by putting 12 volts through the connector pins on the back of the unit? if it gets voltage without anything else being connected would it show at least an error message or 0? I am suspecting that it is dead but would like to prove it without buying a new one....

2 Why would it only be the positive pins that have rusted away in the connecting plugs? the others seem to be fine...

Thanks
Graham

[TwoBob]

If anyone is interested the answer to 1 is no....... Guage shows no sigh of life with a voltage just across the power pins but it is all working fine now that I have repaired the connections in both ends of the tacho harness.

I am still interested though in finding out why it is only the positive power pin that has corroded away at both ends of the harness. Something seems not right about this. One thing that I have noticed is that I can see no termination resistors in this system which it would appear from the installation manuals I have seen on the Internet should be fitted at the engine and junction box. However I would have thought these are more to do with data than power given the descriptions I have read. Anyone got any ideas.......????