Morris Minor Owners Club

Can anyone advise where an after market ammeter needs to be wired into the circuit? My gauge has two wires, and shows both positive and negative currents

John

What year is the car? Is it the later solenoid start (using the key) or older pull start? I have fitted ammeters to both types on my Traveller and saloon respectively. Disconnect the battery earth before doing any work. The ammeter fits into the charging wire from the dynamo or alternator using cable of the same size. On the first type the wire is connected to the solenoid and on the second to the battery terminal. This wire is disconnected and extended to the ammeter and another wire from the ammeter goes to the solenoid or terminal. If the ammeter indicates a discharge when ign. lamp is out then just reverse the connections on the ammeter. There may be a different method but the foregoing is the one I used. I can e-mail a diagram if necessary.

The above is,of course, correct but I would stress that
in fitting an ammeter you have inserted it between
the battery and the wire which carries the supply to the
WHOLE car with the exceptiion of the starter motor.
In other words if you do not make a good job of the
new connections and one fails you will lose ALL electrical
power.

Fortunately the ammeters on both cars have been fine but Willie is absolutely correct with regards to making sure all the connections are of high quality. They have to be capable of carrying a fair amperage especially when lots of extra electrical goodies have been fitted supplied by an alternator. On reflection, and not regretting fitting the ammeters, I could have more than likely made do with a voltmeter with simple red/yellow/green sectors showing battery state. These can be fitted using much smaller wire and connected between a permanent supply and earth.

I reckon you are better off with your ammeters '57' yes
the fitting of a battery condition meter is much simpler
but they don't give half the info that an ammeter gives
do they?

Willie could you expand on the differences / advantages / disadvantages of ammeter vs battery condition gauges

An ammeter will give an indication of the state of the battery, the current load on the system (lights, wipers &c.) and how well the dynamo/alternator is coping with the demands. I think.

A battery condition meter will show you how much voltage remains in the battery. It should stay at around 13v or thereabouts. It may dip a little when the system is under load, but it will really only indicate when the battery is discharging.

Of course, you could just monitor the headlights, and see if they go a bit dim over use

As stated, a battery condition meter measures the voltage
of the battery and will give an idea of voltage drop when
switching on various circuits on the car( for example,a
battery which is losing its efficiency will drop from its
nominal 12v to as low as 9v when the starter motor is in
use)....much lower than this and you will get starting problems.
An ammeter tells much more, like how long it takes to
replace the charge used up in starting the car,wether the
charging system is compensating for additional loads as
they are switched on,pecisely what the current drain is for
each circuit etc etc. The advantage of the battery condition
meter seems to me to be only that it is fitted more easily
straight across the battery!

I've seen a number of digital ammeters which monitor the currrent by just clipping onto the wire (i.e. you don't have to pass cut into the wiring).

However, I've a memory that these will only work on AC not DC. I would have tought that in these days there might be a more elegant way of measuring the amperage flow in a circuit than by simply sticking a meter into the main wiring?

If I recall correctly (this is A level Physics & a long time ago) an ammeter is really a voltmeter measuring the potential difference across a resistor (which has a low resistance so it doesn't limit the current). Just re-calibrate the dial!.

Colin

You can get the external shunt type. You wire the shunt in-series with the load and connect the microvoltmeter across the shunt in parallel. I have seen these units before, but never for automotive use, although I think they were available at some point.

A voltmeter can give you a pretty good idea of charging conditions, too. Most 3 light indicators are just voltmeters, but without enough resolution to see the trends.

An ammeter tells you whats flowing into or out of the battery, and gives you an idea of how well your battery is charging (or how much it's discharging), but it doesn't tell you how much is in there already.

A voltmeter tells you how well the system is coping with the loads on it. If the battery is well charged, and the loads light, the voltage should regulate nicely at around 13-14volts. The Voltage depends on the system, and the age. Modern alternators tend to regulate at around 14.3v. If your battery is low, but the alternator is coping well, the voltage will slowly increase, letting you know things are OK. If the battery is OK, but the charging system isn't coping, it will slowly decrease warning you of imminent problems. A poor battery and no charging: permanently low volts, a good battery and coping well, regulated volts soon after start. It still can't tell you how much is in there already.

You can tell how much juice is in a battery by measuring the voltage, but you have to disconnect it from the car (to remove any continous loads) and leave it for a while after charging to settle. The voltage changes are pretty small too (around 1v between brim fiull and 80% empty if I remember correctly)

Moderns cars that have a gauge, go for voltmeters (VW Phaeton for example).

Older clamp on meters use a transformer, the wire you clamp on acts as a single turn around the core, and these only measure AC. Modern clamp ons use Hall Effect (The magnetism affects a piece of silicon) so can quite happily measure DC. I use one of these and a voltmeter any time I need to check out a charging system.

If you really want to be sure, fit both!

I would suspect that modern cars fit condition meters because
they are easier to fit and because should one go open circuit
there will be no repercussions. Since all modern cars have
Alternators this is an advantage. If an ammeter were fitted
and it went open circuit the Alternator would be damaged
if it was running at the time.

You'd be able to do a cleverer ammeter, as was suggested, that wouldn't break into the line.

With the output of modern alternators, you wouldn't want it anyway, as the wires would be so big. Top end cars have alternators that can produce up to 190 amps, and electrical systems that if run flat out would still out pace them. A couple of big (and I mean big) cooling fans can draw 70A on full chat. Add the air con blowers, wipers, lights, stereo, engine management.......... You know what I mean.

The alternator wouldn't likely be damaged, either. Most recent (10 years or so) alternators are load dump protected. Load dump is when what you say happens: the battery terminal comes off or a main fuse goes. The diodes on most modern machines include zeners which limit the spike that occurs. The things that would be damaged first are any electronics on the car, and this protection in the alternator helps stop that.

So are the above saying if you have a Moggie with an Ammeter & Alternator fitted and the Ammeter goes US it would knock your Alternator for 6

I don't think you'd have a problem with the alternator, but any electronics (Stereo, alarm) might suffer depending on how well protected they are against a very short burst of 200 volts (fractions of a second). The regulator in the alternator might suffer, though.

It's impossible to say for certain, because the power of the surge depends on so many things. If the battery is flat and you have nothing else switched on, if the ammeter did go open circuit, the entire output of the alternator would have nowhere to go, and would be the worst case. Saying that, your battery is likely to be lower and everything working harder when the lights are on, for example. These would still be on (should be on the same side of the ammeter as the alternator) and would absorb a fair bit of the surge.

It's also fair to say the dynamo could do the same thing, but since the output is lower the surge is lower.

In my younger days (when we had to worry about it because we didn't have central protection) I remember testing a control unit that drove a bulb or bulbs (can't remember exactly what it was, it was fifteen years ago). The electronics had been designed cleverly so that the energy always went into the gbulb, not the electronics. Every time we simulated a load dump, the bulb blew but the electronics were fine.

Kevin....Yes probably because I suspect that most Minors
which have been converted to run on Alternators are using
early Mini types Not the improved type mentioned by
lowedb. The Ammeters would probably be the older type
too. But don't get too worried, as long as the wiring has
been PROPERLY modified you are unlikely to suffer an open
circuit.

Fitting an ammeter where the entire elctrical supply flows down a cable into the cab exposes the driver to a higher electromagnetic field. These days with more research being done into the effects of mobile phone radiation and laws about "EMC" compatability this effect has been noted and some companies now take positive steps to route wiring away from the driver in fear of future litigation. This is similar to the problem of fitting the battery in the boot (eg MG), in which case you are advised to run a return earth cable away from the driver rather than rely on the random path taken through the chassis.

Also as mentioned by others there is an increased fire risk bring more high currents inside the bulkhead - but the Minor has so few fuses this is insignificant relative to the existing risk.

So fit a remote shunt type ammeter or a voltmeter if you care, but then if you did worry about safety you wouldn't be driving a Minor in the first place would you!

"washer-bottle",
Don't even start about modern cars being safer than older cars.
I have seen modern cars torn apart due to the metal being so thin. Sure, there might be some types of accidents where the modern car is better off, ie head on crash, but in any car a head on is nearly always severe.
I've been involved in a roll over (no fault of my own) & a modern car would have been squashed flat to the headrests.
I'd rather enjoy my Morries & take my chances avoiding "modern" cars.

Sorry Scott, I'm getting a Yahoo page saying 'This page is not available'. I assume these are pictures of your moggies (Morries as you would say)?

I fully agree with your comments - it's almost folklore in the UK how robust a Morris Minor is. There are risks in any car and I don't believe Minors are more dangerous overall if driven with regard to their limitations. Indeed you could argue that 'safer' cars actually encourage many drivers to take greater risks.

Chris,
What are you doing reading this as this time. It's midday here but 4.00am where you are isn't it !!!
I can look at the "Morries" from this end but I don't know what the problem is if you can't access them.
By the way, no one here calls Morris Minors "Moggies". Must be the Australian translation. Cats are usually called Moggies over here, just don't ask me why though.