Electrical stuff

[steve851]

Ok I' been reading up a bit about Mustang instruments and read that the ammeter on 67/68 rarely works and must of them shat themselves very early in the cars life. The recommendation is to bypass the wire that connects to the Ammeter to prevent an electrical fire occurring in the future. So by the term by passing do they mean disconnect the red and yellow wire and connecting the two together? Now this seems kind of odd to me, as we all know ( by reading our mustang circuit diagrams) the red and yellow wire both come from the Battery side of the starter solenoid. This means there should be power at both terminal posts behind the ammeter, am I right? and if so why does an ammeter require power at both terminals?.
As I have never really had the cars electrical system up and running fully, I am only assuming (from what I've read ) that the ammeter is actually US. I have checked to see if there is continuity between the red and yellow wires to the ammeter and there is. does this mean the ammeter works?
Whilst on the subject of wires etc I also have one of those retro style sound systems to fit. whilst one wire powers via the ignition switch there is another wire which is supposed to connect to the battery (hot) would that afore mentioned red wire to the ammeter be a suitable connecting point for the hot wire to the sound system.

Cheers

[nassi]

I think you should be able to simply disconnect the two wires from the ammeter. No need to short them together. Yes you are right, there is power at both terminals. The ammeter looks at any the slight imbalance between the alternator output and the battery. All ammeters will have power on both terminal as there are in a series circuit.
When you checked continuity, do you mean with the red and yellow wire disconnected and the meter across the terminals of the ammeter? If so then your meter may well be ok.
You could use the red wire input for your stereo constant 12v, just not sure if it would effect the ammeter reading.

cheers.