Amp or volt meter ??

Post by **candy** » Mon Jun 30, 2008 9:58 pm

Hi, can you fit an ammeter to a car with a dynamo or does it have to be a volt meter?

Post by **alex_holden** » Mon Jun 30, 2008 10:00 pm

Yes. Personally I find an ammeter more useful than a voltmeter.

Post by **Rob_Jennings** » Tue Jul 01, 2008 12:45 am

A volt meter will tell you a great deal without all the problems of very high current wiring to the dash for an ammeter.

at the end of the day its your decision. ideally you have both but personally I think a volt meter is sufficient and easier to fit then an ammeter

Post by **Spag** » Tue Jul 01, 2008 8:00 am

Go Volt meter every time...

Both essentially indicate the same thing, but the V has less chance of embarrassing dashboard fires !! (Unless you are going to use a fancy A with shunts (but then it's just a V meter anyway innit ;))

Post by **Kevin** » Tue Jul 01, 2008 9:00 am

Agreed a voltmeter is safer.

Post by **alex_holden** » Tue Jul 01, 2008 9:03 am

Bear in mind the Minor already has a couple of unfused circuits running through the dashboard (ignition and lights). They can catch fire just as easily as ammeter wires if the insulation wears through or a live connection comes off a switch terminal and shorts against the body. Use the correct thickness of wires, pay attention to how you make the connectors, and use grommets where they pass through the bulkhead and it should be fine. Note that this is no more than what you should do when wiring anything into a car...

Post by **IslipMinor** » Wed Jul 02, 2008 9:54 am

An ammeter is definitely more work to fit, especially with an alternator, where the cables are quite thick, and can be tricky to connect and run properly.

BUT, an ammeter tells you exactly the state of play between supply and demand. At its simplest level, anything more than 0A means that the electrical load is covered, and if less it is not! Also, with an alternator, if the net charge rate stays much above zero after a long run, it's time to check out the battery condition, or less likely the voltage regulator - dynamo regulators are not so precise.

A voltmeter tells you whether the alternator is putting out a charge, but is there a point when can you be certain that the applied eletrical load is being covered? Is it 12.5v, 12.7v, 13v or what? Equally when should you start being concerned at overcharging?

I have always fitted an ammeter, it's unambiguous and I much prefer it - but as always it's a personal 'thing'!!

Post by **Spag** » Wed Jul 02, 2008 11:26 am

The unfused stuff behind the dash is all fairly light gauge compared with looping the 10mm(?) battery feed through, so the potential for frying a lot of stuff before the cable melts itself open circuit is a bit higher

That said, if properly installed, then no worse than fitting a battery master switch in the dash... Hmm must find a suitable space for one in William...

My point being that for most people, a V meter will tell you enough to know the state of the charging system, with an easier install.

If you know that your batt when charged sticks out 12.8V, then if it reads less than that you are loosing juice somewhere when the engine's not running.

If you know that your alternator normally sticks out 14.2V, then if it's lower than that there's summat nicking juice, when running, and if it's less than 12.8V you know you isn't charging at all. 15+ means mad alternator which will soon explode

Post by **Welung666** » Wed Jul 02, 2008 12:19 pm

Spag wrote:Hmm must find a suitable space for one in William..

Sorry to hijack but this is where I've fitted mine...

I did it this way so I didn't have any heavy wires passing through the bulkhead.

Post by **candy** » Sun Jul 06, 2008 11:36 am

Well thanks for that info, But you know the next question is now that i went the amp meter way (smiths) , it came with no fitting instructions but did come with the correct thickness of cable (two big black cables with spades at one end and rings at the other. I know that an amp meter is connected in series and a volt meter in parallel ? but the diagrams i have seen show a cable from one side of the meter to the dynamo and the other from the meter to the battery. This sounds like
adding another parrallel circuit to me?

Post by **Alec** » Sun Jul 06, 2008 11:54 am

Hello Candy,

the original feed from the dynamo to the battery connection actually comes from the regulator A terminal (As does a second cable which feeds one of the fuses) and connects to the solenoid battery terminal. This is a brown thick cable. The ammeter needs to go in that cable, I would suggest as you have new cables with your ammeter that both ends of that cable are disconnected, taped up and secured out of the way. Connect one of the new cables to the A terminal on the regulator (from ammeter negative) and the other to the solenoid battery terminal.
Do try and get rubber boots to fit over the ammeter terminals and where the cables pass through the bulkhead are grommeted or else pass through an existing grommet. Cable tie them securely to avoid excessive movement.
When you switch the ignition on the ammeter should register a discharge, if it shows a charge it is connected wrongly, merely reverse the connection, this corrects the polarity of the meter.
Alec

Post by **candy** » Thu Jul 10, 2008 8:45 pm

Ive, only one cable from A but have more from A1, whats the difference??

Post by **bmcecosse** » Thu Jul 10, 2008 10:13 pm

Just trace the heavy brown cable from the solenoid switch (or battery if it's a pull start ?) - that's the cable you will replace with the ammeter cables. A1 is used for headlamps - it automatically boosts the charge from the dynamo when headlights are on.

Post by **bpr81a** » Thu Jul 10, 2008 10:25 pm

bmcecosse wrote: A1 is used for headlamps - it automatically boosts the charge from the dynamo when headlights are on.

You learn something new everyday on here!

Post by **mike.perry** » Thu Jul 10, 2008 10:28 pm

Now that we have established how to wire in an ammeter could someone please tell me how to wire in a volt meter to a M 1000 with alternator and of course neg. earth.
I already have an ammeter in the series MM.

Post by **bmcecosse** » Thu Jul 10, 2008 11:52 pm

Just connect it through the ignition switch and to earth! If you don't use ignition switch - it takes a small current all the time and will soon have the battery flat!

Post by **Alec** » Fri Jul 11, 2008 1:41 pm

Hello Mike,

you need an ignition feed, and probably the best is one of the green auxiliary cables, such as the voltage regulator supply (Just note that it is not a light green as that is the regulator output). This is an ignition feed but fused. The other terminal (negative) is connected to earth.

Very simple.

Alec

Post by **mike.perry** » Fri Jul 11, 2008 11:00 pm

Thanks for that folks. One slight snag, with an alternator there is no regulator box, still I got the principle. I wired one terminal to the ignition fuse input and the other to the inst. panel fixing scew, turned on the ignition and hey presto (what ever that means) 12 and a bit volts.

Post by **PSL184** » Sat Jul 12, 2008 12:16 am

mike.perry wrote:One slight snag, with an alternator there is no regulator box.

Oh yes there is

Well, mine has anyways.....

Post by **Alec** » Sat Jul 12, 2008 7:08 am

Hello Mike,

you would be better connecting to the fuse output, as this will protect the meter and wiring.

Alec