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MG MGA - a laymans question

What is the difference between an ammeter and a voltmeter, and how are they used? What would be best for me to use to check electrical instruments?
Nigel Munford

An ammeter measures current (Amps), and a voltmeter measures voltage (Volts). These are not used to check electrical instruments, but to to keep a constant watch on the amount of current being fed into the electrical system, and the total battery voltage at a glance.

F. Camilleri

Nigel, you can tell much more about your charging system with a voltmeter than you can from an ammeter.

Check out mga guru for the full explanation but basically it like this.

An ammeter will show you the rate your battery is being charged or is discharging, but not how well the charging system is performing.

A voltmeter will give you a much accurate picture.

With the engine not running the battery voltage on a fully charged battery in good condition should be in the region of 13.2 to 13.8 volts.

With the engine running a generator will give you approx 14 volts output and an alternator will give 14.2 to 14.5 volts, once the engine is running at say over 1500 revs.

Also a voltmeter will show you if your voltage regulator system is working correctly which can be critical if you have an electronic ignition unit, fitted for example. Modern electronics are very voltage sensitive and anything over 15 volts may burn out any electronic equipment you have installed.

So I would say that if you wish to fit either of them, fit a voltmeter.

c firth

Nigel, if you are checking electrical equipment, as opposed to installing a meter in your dash to monitor the battery, I suggest you buy a multi-meter, which will measure volts, amps and ohms resistance by selector. They are quite cheap and reliable, for use on the bench or wherever.
Art Pearse

This thread was discussed on 25/08/2014

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