How do you wire in aftermarket ammeter

I want to wire in an aftermarket ammeter and am not sure exactly where I snip the line and wire the ammeter in series. Can I wire it in series with the 12Volt line that goes to the alternator?

What is the standard procedure with vehicles that already have factory installed ammeters, what circuit are they in series with?

Denny B

Reply to
Denny B
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Reply to
Mike Walsh

I don't have my schematics handy but I remember that factory ammeters hook up between battery/alternator and electrical system, generally in the engine bay fuse box. This isn`t an ammeter I'm talking about, it`s a current sensor fed to the engine computer.

If you're trying to see alternator load your best bet is wire it in series with the 12-volt line that goes to the alternator.

Tibur

Reply to
Tibur Waltson

First find out if it's a true ammeter - wired in series. True ones have two (heavy) studs on the back and are spliced into the output wire of the gen/alt. Most vehicles from the 70's up don't use this one because your sending unfused power in and back out of the passenger compartment and it requires a heavy wire - at least as heavy as the alt output wire. Heavy wire costs money and the car makers don't want to spend a nickel. I'm sure there are other reasons, such as voltage drop, fire hazard, new technologies, voltmeters tell you more, etc.

The other unit is a voltmeter that lookes like an ammeter that measures voltage drop and is expressed as amperage - and is wired in parrallel. It usually is wired (16-18 ga wire) at the output terminal of the alt and at the accessory side of the igition switch - shuts off when the key is out. The terminal ends on this unit are small, usually spade connectors (but not always). Do Not wire this one in series.

Why would want to install an ammeter instead of a voltmeter? The voltmeter just wires into an accessory feed (power on with ignition) and a good ground - all of which is inside the car.

Pete

Reply to
pete selby

Okay, after checking a schematic, I got it wrong. The factory ammeter loops around the thick wire between the battery and the ignition switch, just like Mike pointed out.

Tibur

Reply to
Tibur Waltson

That would be an inductive ammeter. Mike's is one that uses the voltage drop to estimate the amount of current going through the wire. The problem with that design is that current is being limited by the size of the wire and the voltage drop that would be created.

Reply to
Bruce Chang

"That would be an inductive ammeter"

This is correct it is an inductive meter.

Denny B

Reply to
Denny B

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