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MG Midget and Sprite Technical - Voltmeter or Ammeter

If fitting either an ammeter or voltmeter gauge to a Mk2 midget, 1098cc engine (with dynamo), which is likely to be more useful, an ammeter or voltmeter?
Also, given the car is postive earth, do I have to be aware of any polarity issues when buying one of these gauges? I assume the voltmeter won't, as it's just connected in parallel with the battery, but what about the ammeter?
Adrian

Adrian, i cant comment about the positive earth but when it come t prefference i would advice a voltmeter as i have done myself.
This way it easy to see for me what the extra rallylights i have on my car do with my battery and if my altenator/dynamo can cope or not(it does when driving but at idle i have to switch of these lights) and i was able to tell that my altenator/dynamo stopped working during a trip in wales because my voltmeter dropped to 11 otherwise i would have driven on untill my battery was empty/died.

Arie de Best

Ammeters go in series with the battery connection - with one important proviso - but excluding the starter-motor, which draws too much current.

In the alternator cars, you should connect one terminal to the solenoid 'alternator' terminal and the other to the alternator supply / main brown feed to the loom. Similar connection in principal to the dynamo cars.

A voltmeter is easier, since you're not taking live / heavy / unfused wires through the bulkhead onto the gauge terminals. And you can get a lot of info from the volts reading - it just needs more interpretation.

+ve earth makes no different - if the guage reads the wrong way just reverse the connections.

A
Anthony

Voltage gauge every time, much less chance of a nasty melt down..
K Harris

Used an ammeter for 39yrs on my Frog. Also have a voltmeter but prefer the ammeter.
Alan Anstead

There's nothing like an ammeter for letting you know that you are spending more than you are earning however you are carrying the full might of the battery through the grounded bulkhead.

You must be very sure there is no potential for chaffing or shorts or you could lose your car very quickly.
Jeremy Cogman

It is your choice.
With a dynamo, since you generally are running off of the battery at speeds under 2k rpm or so, an ammeter conveys useful information regarding when you are running at a deficit vs when you are actually charging the battery.

With an alternator, a voltmeter is more useful, since it can show the current state of charge of the battery as well as indicting when the alternator is working correctly and when it is over-charging, etc.

You can always install both... Or install an alternator.
David "voting for the ammeter" Lieb
David Lieb

DITTO on all the above.

prop
Prop

Thanks for all the replies, they're food for thought.
If I go for an ammeter, will a gauge with a range of -30=0=+30 be sufficient for a dynamo charging system?

Adrian

Yes; will be fine

A
Anthony

The link below has a good explaination of which gauge to use. Short answer is go with the voltmeter. http://www.autometer.com/tech_faq_answer.aspx?sid=1&qid=5
J Bubela

Ahhh, but remember, it has been so long since dynamos ceased to be installed in vehicles that the author of that piece does not so much as mention them. The presence of a dynamo changes the situation dramatically. As I stated above, an ammeter provides more useful data regarding the day-to-day function of a dynamo than a voltmeter does. For diagnostic purposes, however, a voltmeter is sometimes more useful.
David "the stickler" Lieb
David Lieb

This thread was discussed between 22/04/2008 and 24/04/2008

MG Midget and Sprite Technical index

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