I noticed with the engine is running the rev counter stops working when the lights are switched on. Turning the lights off starts the rev counter again. Any ideas..? I'm not great with electrics. Also the amp metre doesn't work at all. How should this be wired up...?

Ed

Probly bad earth somewhere on yr headlight circuit robbing the earth from yr tacho.

Ammeter needs either the main battery lead across it, or you need to the brown wire(s) as they come away from your solenoid - before they power anything else. Basically, the ammeter is then a part of the main power circuit of the car and measures the total current being drawn from the electrical system. Can therefore be a nightmare if you get a dodgy connection on it.

I'm not an electrician either but I do know from experience with another car, that since it is essentially wired directly inline with the battery (displaying everything going in and out at any time) you must be very carefull that the wires are big enough to carry the maximum current of the system the same size of wire which goes from the battery to the side contact of the solenoid for the starter. In fact the ammeter will finish up being wired in that line (please get advice) and that it is not fouled by anything else behind the dashboard which could possibly short it out to earth, even the clamps that hold it to the dashboard panel. Don't forget it will all be live behind there even when everything else is off so you need to insulate the terminals so they can't short out. If it's not done correctly you could finish up with a big fire very quickly indeed.
Sorry to sound so freaky but better safe than sorry.

If I were you I would seriously consider removing the ammeter and wiring in a voltmeter (Battery condition indicator) instead.

An ammeter is fitted in series with the main power lead from the battery. The only power that doesn't go through it is the starter motor current. All the warnings in the above posts are true.



A voltmeter is connected in parallel with the output from the ignition switch so it is not powered when the ignition is off. It carries only a tiny current and gives you basically the same information as an ammeter.

Am I wrong in thinking that you could also wire it to the large terminal on the alternator (the one with the rubber boot) using normal cable and earth the other side? You would then see how the charging system was coping with the load. The Smith's ammeter that I have ready to fit doesn't look as if it has the right terminals to take heavy cable and I'm sure that when I bought it on ebay from the Gauge Shop that the instructions said to wire the above way - problem is that I can't find the damned things now...

Be very careful here.
If you wire an ammeter +12v on one side and earth on the other, then you'll create a dead short = at best, a very flat battery and some very burnt wires VERY quickly !! Worst case the whole thing goes up in flames
Ammeters really are potentially a very nasty thing, as several have pointed out.

Sounds like a Voltmeter you have there!

That's true!!

Yes, for a voltmeter that sounds much more reasonable.
I still wouldn't wire one up quite like that though - I'd rather know the voltage at the main power supply. Off the switched power into the fuse box for eg.
You don't really want any gauges live all the time.