Ammeter with a shunt resistor

[ALAN COCHRANE]

Hi Everyone

I've been thinking of ways to remove the danger of all the car's load going through the ammeter, since my previous one went open circuit.
To this end has anyone used a shunt resistor in tandem with the Lucas Ammeter and if so what internal changes are required to get it to work?

I realise that a voltmeter would be the easy option but I'd rather retain the ammeter for originality's sake.

Cheers

Alan

[cactusman]

Tricky. The ammeter is calibrated (well is supposed to be anyway) to read plus or minus 30 amps (or what ever yours reads) so adding a shunt resistor will mean the meter severely mis reading. You would need to have the meter innards removed and replaced with a sensitive milliamp meter in conjunction with a suitably dimensioned shunt resistance.
The innards of the lucas ammeter is very crude...just a loop of wire carrying the current next to a magnet that moves the needle. By now safe to assume that any Lucas meter will simply wobble to show a charge or discharge, The chance of it accurately reading the current is remote. My 3.8 does this but i have fitted a volt meter separately that provides a much more meaningful indication of the battery condition. Look for about 13 to 14 volts when the engine is running.
Good luck anyway? J

[Alty Ian]

Hi Just fitted a voltmeter to replace the ammeter in my S1 4.2.

As all the 5 wires going to the ammeter are -ve am I right in assuming that connecting them as below is correct.

ammeter terminal one has

a) Brown/white (alternator)
b) Brown/white (Ignition switch)
c) Brown/white (light switch)

ammeter terminal two has

d) Brown/red (Ignition switch)
e) Brown (Battery terminal post)

Action to isolate above prior to fitting voltmeter is

1) Join together and insulate a), d) & e)
2) Join together and insulate b) & c)

Before I make it live is this correct?