what is a "shunt"

[bloxman]

Ah so my car is missing it's shunt so ..

1) my ammeter doesn't work (I thought it was busted!)

2 I don't know what one looks like (cause it missing remember?) , any one have a picture of their shunt?

3)I have no idea where to get a replacement unit.

4) could one conceivably build one?

Using the search:

I found this only relavent reference to shunt)

" on my 75-280 I only have 1 fusible link box, located on the relay bracket.

Underneath this box, is a metal box, 2" x 2" x 6" and it

contains a copper strip, shaped like a "m", and 2 glass

fuses. 2 large gauge wires ( 8ga maybe ) one white and

one white/red connect to the large metal strip, and 2

light gauge wires, same colors, connect to the 2 glass

fuses.

My question is : is this unit the fuse for the charging

system ? Thus can be replace by 60 amp fuse.

FSM shows 2 normal fusible link boxes, but this metal

box appears original,connects to harness ,etc.

Voltage regulator is mounted underneath this relay

bracket."

So he never got a clear answer to his question can I replace the shunt with something I could make?

[SteveJ]

A shunt is an alternative current path. For instance, if you wanted to measure the current flowing through your battery while your car is running, you would put in a shunt in parallel to your ammeter before starting your car. After starting your car, you would remove the shunt. If you didn't have the shunt in place, all of the current at start-up would flow through your meter, and bad things would happen.

[bloxman]

Sounds frightening!

So the shunt is there to protect the Ammeter during start up.

Aside from a replacement shunt what can i put in there?

what makes the current go through the shunt instead of the ammeter? A big resistor? That would make the current flow through the shunt instead wouldn't it?

[Zedrally]

Ah so my car is missing it's shunt so ..

snip..

So he never got a clear answer to his question can I replace the shunt with something I could make?

The easiest way of replacing the shunt is by finding a replacement from a donor.

There is no way that I'm aware of, that you can make one as it is a mathematical predetermined (length*width*depth) piece of metal that has a known resistance.

[bloxman]

So any ideas where Ican aquire a shunt?

I live in Grenada in the Caribbean so I do not have access to hundreds of Z's that are just lying around.

Bloxman

[Walter Moore]

Sounds frightening!

So the shunt is there to protect the Ammeter during start up.

Aside from a replacement shunt what can i put in there?

what makes the current go through the shunt instead of the ammeter? A big resistor? That would make the current flow through the shunt instead wouldn't it?

Actually, no.

The shunt is a calibrated resistor that is always in the circuit. The "Ammeter" is actually a very sensitive voltmeter that is constantly measuring the voltage across the "shunt".

If your shunt is missing, and the car still runs that means that the Ammeter has been by-passed. Without the shunt the ammeter will not carry enough current to power the car. (and as was pointed out earlier without the shunt the ammeter could burn out very quickly)

You didn't mention what year of Z car you have. On the early cars 70 - 73 or so the shunt is actually mounted on the back of the ammeter. If I remember correctly on the later cars it is mounted in the engine compartment somewhere. (The higher output alternators on the later cars made mounting the shunt in the dash a fire hazard.)

In either case, if the problem is that the car does not run BECAUSE the shunt is missing, the simplest solution is to replace it. You can also jumper around the ammeter, but if you do use a BIG wire as it will have to carry all the current to power the entire car. (Except the starter)

[=Enigma=]

Sounds like the quickest path would be to find out what year cars they are, what it looks like, and have someone locate one for you here in the States, and have it shipped to you.

[TomoHawk]

He's right. the shunt is a really heavy-duty resistor of a value that using the equation V=I * R, or I=V/R, where you know V=12 volts, and the shunt is (so many ohms), the ammeter shows you the Amps flowing from the battery.

I've seen people make shunts from combinations of resistors(both prallel & series). You're best off getting the right part from a good source.

[sblake01]

His car is a 75 280Z which, I believe, still had the ammeter rather than the voltmeter like a 76-78. If I knew where to look on the car for the shunt, I could try to find one for him on my next junkyard trip since I think they have a 75 at the local Pick a Part.

[V8-240Z]

I found this doing a search http://www.zcar.com/forums/read.php?f=1&i=427262&t=427262

On my 71 240Z I replaced the 45-45 amp meter with a volt meter from a 77-78 280Z. Any of the high output alternator conversions will overload the stock shunt and burn it out like a fuse. The Voltmeter swap was a bolt in. I even wired in the red charge light that is in the volt meter face.

[TomoHawk]

Of all the ammeters I've seen (all domestic ones) the shunts were attached to the terminals on the back of the ammeter. They were just strips of metal. they could conceivably be anywhere on the ammeter circuit.

[Zedrally]

Wasn't it part of the voltage regular box?

There were 2 fuses in the same package..