Installing an Ammeter

[Talasas]

Hi there guys,

I've started installing an ammeter to keep tabs on load. I'm a little stuck as I'm not quite sure where I'm supposed to be taking a reading from, I've read three different guides (inluding the gauge's pdf) and they all say different things. I'm in a bit of a mess as I wanted this done today.

Does anyone know where I take the readings from? I know it's supposed to be from the alternator and anything that isn't the starter motor. Also which can I assume is positive, the diagram on the gauge's pdf doesn't make sense:

http://www.egauges.com/pdf/Isspro/IS014.pdf

On page 2 there's a diagram but it shows positive battery terminal to negative gauge terminal and alternator output onto positive side?

Totally confused...
Car is an AE93 SX

[CrUZida]

If you look at your battery you'll have one fat wire that goes straight to the starter, and one or 2 wires that go to the rest of the car.

Remove these one or 2 wires (leaving the fat starter wire on the battery) and put the ammeter between those and the +ve terminal.

[Talasas]

Well actually I see about 5 wires. Can I have the ammeter placed just after the node where it meets the starter or will that still read the starter current as well?

[Norbie]

Basically you want your ammeter to go between the battery terminal and the car's wiring excluding the starter cable. You may need to re-arrange your battery wiring to acheive this but it shouldn't be too hard to do.

[mic*]

Never used one of these...

Cant they handle starting amps? Otherwise whats the biggy with having a spike when you start you car?

[ndgcpr]

if it can take around 200+ amps then i guess it is ok. If its a mechanical gauge then they are usually achieved by running as weak motor and springs, to much surrent will send too much voltage to the gauge and brake it, failing that your "sender" will have too m,uch current flowing through it and act as a fuse and brake.

I have never really worked out where i would want to put one on a car, if its on the lead to the alternator then you will see current only when the car is running and you will know instantly when your alternator is failing.

Running it into your fuse box for example will show most currents but not sure additional amps going to external amplifiers or anthing, it will also not let you know if you battery is getting flat and absorbing most of the current produced from the alternator.

[hemi twofifteen turbo]

Put it just after the battery terminal on the SECOND fattest wire. positive (+) values indicate the magnitude of the current going into the battery (charging). Negative(-) values indicate the magnitude of the current coming out of the battery (discharging). I think in toyota's the main positive feed wire is white but I could be wrong. turn your headlights on, and remove wires from the terminal until they turn off, then you've got ur wire.

[Talasas]

Okay thanks to all who helped. I managed to figure it out with the advice I was given here.

It is a bit unclear but it clicked once I drew myself a circuit diagram. Basically there are "two" wires coming from the positive side of the battery. One wire (thick, single wire) runs straight to the starter. The other wire (on AE92s has 3 fuses BTW) runs everything else and can be seen going directly into a fat section of the engine loom.

I dismantled the positive battery terminal and isolated the "loom" wire complete with fuses. The section left over is the starter wire, I re-assembled the positive terminal and left this on.

The now isolated section will have the ammeter between it and then positive terminal. The key idea here being there is no negative or ground to deal with as an ammeter must be wired in series with all the other elements. This leaves you with two wires, one "IN" and one "OUT". In detail "IN" goes from the positive battery terminal to the negative terminal on the ammeter (it does vary between brands so if you get a backwards reading simply reverse the poles). "OUT" goes from the positive terminal on the ammeter back to the isolated loom section.

Other key things to note, I used DSE 8-Gauge Wire which is rated at 56 Amps Nominal and 150 A peak, that should be enough since the car should go over +/- 15 A very often when charging/discharging. The wire itself looked about as thick as the wire that runs to the starter, but keep in mind that only runs for a short time, this has constant high current running through it. I wanted to be safe and have the wires keep cool.

Materials cost me:

Ammeter Gauge: $75 imported
4 metres of high current wire: $10
Pk.10 Ring Terminals: $2.80
4 Toyota spare globes with blue silicone: $10 (rip-off)

the rest was stuff I had lying around.

Thanks for the help people. If anyone needs help with this let me know

[CrUZida]

The key idea here being there is no negative or ground to deal with as an ammeter must be wired in series with all the other elements. This leaves you with two wires, one "IN" and one "OUT".

I'm guessing you didn't know this before hand, and didn't realise this when you saw the diagram.

Perhaps I should have explained this earlier.