Burnt tach

First post burnt the red wire from the pextronix unit when it grounded against the advance plate in the dist. Which burnt the tach,I've spliced in replacement wires and am wondering if I can by-pass tach or is there a resistor or something in the tach?? If I hook the wires that would normally have a tach in between the car runs, unhook won't start. So do I need a tach,or will I burn something else up? 1970 mgb gt stock with only a pectronix unit Respectfully submitted Norman L. jacob

You should update your profile to show the year of your car - saves typing.

You are perfectly safe in connecting the tach wires together - you won't damage anything.

But how much current did you put through the tach itself?! The connections in the tach just go to an internal wire that loops twice around a transformer. The wire is about 18 or maybe 16 gauge. You must have put a lot of current through to burn out that heavy of a wire.

The good news is that heavy current shouldn't damage the tach (other than the shunt wire). Open it up, make sure the shunt wire hasn't just become disconnected. If it is burned out then replace it with another wire, looping as per the original.

The voltage was enough to smoke the tach ,what ever the voltage at the red wire at pectronx unit has at the dist. White wire at dist. burnt about 3" and about 3" both sides of tach. Good smoke. Longer story than I can type out right now. Daily driver 200 miles ,5 days a week ,bought house,moving,disinagrated #3 piston must keep working and move , fix b real busy time and know nothing about computers. Have observed folks here y'all are really swell. Respectfully Norman L jacob

Norm,
I have seen a short of the distributor wiring smoke the tach and much of the harness behind the dash and in the column. The white leads are unfused and should be treated VERY carefully.

What I'm saying is that the wire inside the tach is as thick as the wires leading to it. So, if you put enough current through the tach to burn out the wire, it should also have damaged the wires leading to it.

Do you have an ohmmeter? If so, measure the resistance between the male and female bullet connectors on the tach. It should be near 0. If it is infinity, the wire is burned out but is easily replaced.