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914World.com _ 914World Garage _ -30 to +30 Amp meter

Posted by: brer Aug 2 2005, 01:59 PM

anyone know how these things work?
it has

+A and +B large power connections on it.

any electricians out there?

i can post a photo later tonight if needed

Posted by: Dr. Roger Aug 2 2005, 02:07 PM

they work in series.

just pop out the fuse for the circuit in question.

make sure the amp meter is set on high. (you adjust down later after getting leads on correctly)

one lead to one side where fuse was, other to the other.

watch meter. if it barely budges drop scale to next level.

Posted by: ClayPerrine Aug 2 2005, 02:11 PM

IIRC... an amp meter has to go in the line between the alternator and the battery. On a 914 that would involve major rewiring.

Someone correct me if I am wrong.....

Posted by: lapuwali Aug 2 2005, 02:13 PM

I suspect he means a dash gauge, not a handheld meter.

The best place for dash ammeters is on the shelf. They're generally not a good idea in a car.

The way they're supposed to work is they're placed in series between the battery and the alternator, so ALL of the charging current flows through them. They MUST be adequate for the max current, which is 55 amps on stock 914 alternator, not 30. You need BIG (like 10 gauge) wires running all the way from the alternator, up to the dash, and back to the battery. If you insist on using this, keep a fire extinguisher in the car.

Use a voltmeter instead. This will tell you if the charging system is working. It should read 12.5 v key on, engine off. 13-14 volts engine on, and 9-ish volts while cranking.

Posted by: Dr. Roger Aug 2 2005, 02:21 PM

QUOTE (lapuwali @ Aug 2 2005, 12:13 PM)
I suspect he means a dash gauge, not a handheld meter.

The best place for dash ammeters is on the shelf. They're generally not a good idea in a car.

The way they're supposed to work is they're placed in series between the battery and the alternator, so ALL of the charging current flows through them. They MUST be adequate for the max current, which is 55 amps on stock 914 alternator, not 30. You need BIG (like 10 gauge) wires running all the way from the alternator, up to the dash, and back to the battery. If you insist on using this, keep a fire extinguisher in the car.

Use a voltmeter instead. This will tell you if the charging system is working. It should read 12.5 v key on, engine off. 13-14 volts engine on, and 9-ish volts while cranking.

on the shelf. exactly. =-)

hand held ammeters are great for tracking down shorts or to find out why fuses are blowing. maybe wiring that new fuse box and wondering what size fuses to install...

Ammeters consists of a heavy wire wound as a coil and when current goes through it a magnetic field causes a pointer to move inside the ammeter and the scale is measured in amps.

Posted by: Demick Aug 2 2005, 02:44 PM

Sometimes for a dash mounted ammeter, they have a shunt that is installed between the battery and positive lead. The 'ammeter' then measures the voltage drop across the shunt and figures out (and displays) how much current is going through it. That way, you don't have to run the current of the entire car through the ammeter.

Demick

P.S. not sure if 'shunt' is the right word.

Posted by: brer Aug 2 2005, 02:57 PM

yes this is a period dash guage i have, it matches my silver dot guages. I have an oil press. and AMPS both matching, so i liked the idea of using them both.

This guage has two approx. 10ga. ring hookups on the back, and running in circuit would make sense to me. one red/white dash wire, one solid red wire.

Didn't realize it was a foolish thing to do.

But it sure looks cool!

What if the battery was relocated to the trunk?

Posted by: lapuwali Aug 2 2005, 03:08 PM

Period meaning for older Porsches with 25 amp generators on them (356/912), or old British stuff with similarly limp wristed charging systems. On a system that regularly handles more than 30 amps, you'd blow up that gauge, and most likely would take your charging system out with it.

Posted by: brer Aug 2 2005, 03:19 PM

riiiiiight. I think its clear now.

put the guage in the car when no one is watching.