Ammeter stuff

The + and - readings by the ammeter should be:

Current from battery eg lights on and engine off is negative deflection of needle. when engine running and supplying a charging current to the battery is positive deflection of needle.

Richard Penalurick

Editors note: the +/- of the ammeter depends on whether you think a drain on the battery is a positive or a negative thing ;)

Ammeter wiring

Since you are going to be putting a lot of amps through the ammeter (everything except the start motor goes through!) you will need a sufficiently thick wire. I asked one of my knowledgeable friends about this, and he said that the rule of thumb is 1mm sqr per 10A will work, but the wire will start getting warm/hot.

A typical alternator will put out about 50-60 amps, and a typical ammeter will read to about 60Amps (though apparently you can get ammeters that will read all the way to 130amps -- both ways!). So basically you will be needing a cable that's at least 6mm sqr.

I don't know about this, but I also think it might be a good idea to fit a fuse to the cable going from starter solenoid to the ammeter. Running 60 unfused amps through the inside of your car doesn't sound very good. Though this might be a problem since I don't know if you can get a fuse that large anywhere.

As for cable supplies, I just saw some in an electronic store that sells electric and electronic supplies. Very nice cable, designed for car amplifiers and hifi systems. Should have low resistance too! Here is a link to everything autoelectrical courtesy of Amazon!

On a final note, please remember to disconnect the battery when doing any electrical hookups in your car!

Ammeter, wiring instructions

It goes between alternator/car +ive and the battery/starter lines.

When the car starts, the current flows from battery to starter, and NOT through the ammeter.

When the alto is producing enough current to feed the car, nothing flows through the ammeter to the battery. Hence ammeter reads zero, which is correct.

When the car draws current from the battery (eg: main beam on) then some current flows from the battery to the car through the ammeter, hence ammeter reads +ive, which is correct.

When the alto is charging the battery, current passes through the ammeter the other way to the battery, and it reads -ive.

The big trick is to get the ammeter to read everything except the starter. This is done by keeping the (~150A) starter motor on the 'battery side' of the ammeter.

Ammeter, wiring instructions (II)

Main lead from battery to solenoid remains un affected so the starter current DOESN'T go thru it

WIRES to ALL other things from the downstream side of the solenoid EXCLUDING THE STARTER go through the AMMETER,

ALTERNATOR is on the downstream (-) side of the ammeter so...

If ammeter shows (+) deflection the battery is being charged if (-) battery is being discharged

Starter is fed from solenoid NOT thru ammeter.

Ammeter, wiring instructions (III)

Here are a couple of hints which might help. This is the way that I have hooked up mine and it works OK. This *may* be different for some models as I am referring to a 1975 Clubman.

• Get enough *thick* wire to run into and out from the amps gauge to the solenoid

• Hook the wires to the back of the amps gauge using the correct connector

• Make sure that this wire is not going to rub through on the body and short out or short out at the back of the gauge

• Disconnect the battery

• Disconnect all the wires from the battery cable end of the solenoid

• Leave the starter end of the solenoid intact

• Hook up the battery cable and *one* end of the previously mentioned *thick* wire from the amps gauge using the correct connector to the battery side of the solenoid

• Hook the rest of the wires that you originally took from this connector to the other end of the previously mentioned other *thick* wire from the amps gauge

• Hook up the battery loosely and watch for smoke. All being well, there should be none

• *wallah!! one functional amps gauge. If the gauge works in reverse swap the connections over on the back of the gauge.

• Thnk about also fitting battery cutoff switch if you are leading big fat unfused cables into your passenger cell.
• You might just be better off with a voltage gauge/ voltmeter.

A word of warning. If you are unsure *exactly* what you are doing ENLIST THE AID OF SOMEONE WHO KNOWS WHAT THEY ARE DOING!!! Amps gauges and their associated wiring can/will cause your car to catch on fire if not done properly.

IMHO to pay an auto electrician to do this *can* be money well spent.