Mitch,
Good description, thanks!
I have a GM alternator on my 67.5 that I connected to the stock
harness, but replaced the 30A ammeter with a 60A unit out of a 280Z.
This is temporary until I get time to rebuild my wiring harness, removing
the ammeter and installing a volt meter. It seems that the late 280Z volt
meter will fit in the case of the 67.5 ammeter, so I don't have to put up
with extra gauges under the dash.
This volt meter also has a charge idiot light in it that I will hook up
also.
Peace,
Pat
- Support Habitat for Humanity, A "hand up", not a "hand out" -
Pat Horne, Network Manager, Shop Supervisor, Future planner
CS Dept, University of Texas, Austin, Tx. 78712 USA
voice (512)471-9730, fax (512)471-8885, horne@cs.utexas.edu
On Fri, 2 Aug 2002, Mitch Planck wrote:
> I copied this from the Autometer.com website. I tried to just put a link but
> couldn't because of the way they use frames... It seems appropriate with all
> the alternator swapping that's going on. This is from their Tech Tip
> section:
>
> Caution:
> Use ammeter only on an alternator with a maximum output of 60 amps or less.
> Higher output alternators must use voltmeter.
>
> Which is better for monitoring a vehicle's electrical system - a Voltmeter
> or an Ammeter?
> Short answer:
> A voltmeter, by far.
>
> Electrical guru Mark Hamilton of M.A.D. Enterprises points out that amperage
> is a measure of current flow, so an ammeter is actually a "flow meter"
> that's intended to measure current flow to the battery (under normal
> conditions) or discharge from the battery (in the case of alternator system
> failure). On a typical flow meter, all output must be directed through the
> device to obtain an accurate reading. In the ammeter's case, that means all
> the alternator output used to recharge the battery must first be routed
> through the ammeter under the dash. Which requires a heavy-gauge cable and
> presents a possible fire hazard. And the ammeter itself must be able to
> handle all this current flow, so it must have a higher current rating than
> the alternator's maximum rated output.
>
> All this might be worth the hassle if the ammeter produced reliable
> information. But the ammeter can only measure the amount of current output
> to the battery for recharging purposes: When the alternator recharges a
> "low" battery, the ammeter indicates a high charge rate; with a fully
> charged battery the voltage regulator reduces alternator output, and the
> ammeter is supposed to indicate a very low charge rate. But how can you
> really tell the regulator has reduced alternator output because the battery
> is fully charged? Maybe a diode in the alternator rectifier failed, or the
> alternator belt slipped after it warmed up, just as if the battery were
> fully charged. Or maybe the meter indicates a medium charge rate most of the
> time-does the battery want this much or could the voltage regulator be
> overcharging the battery?
>
> On the other hand, a voltmeter works like a fuel pressure gauge-but instead
> of measuring fluid in psi, the voltmeter measures electrical system pressure
> in volts. Just like a fuel pressure gauge, a voltmeter only needs to tap
> into a circuit; all the fuel (or electricity) does not have to detour
> through the gauge itself. Voltmeter installation is easy, quick, and safe:
> It hooks up to a fused, ignition-switched "off/on" source and does not
> require any modification of the circuit used to recharge the battery or any
> part of the alternator/regulator system. In short, the voltmeter installed
> at the dash will be a stand-alone circuit.
>
> The voltmeter directly measures the result of charging-system performance.
> With normal alternator/voltage-regulator function, battery voltage is
> maintained at 14.0 to 14.5 volts-and this is reported directly by the
> voltmeter. In the event of alternator-system failure, voltage will be low
> and continue to drop as the battery discharges. In the event of an
> "overcharge" condition, the voltmeter will climb above its normal zone. In
> summary, there is no chance for misinterpreting a voltmeter's readings as
> can happen with an ammeter.
>
>
> -Mitch
>
> /// datsun-roadsters@autox.team.net mailing list
> /// Send admin requests to majordomo@autox.team.net or go to
> /// http://www.team.net/cgi-bin/majorcool
> /// Send list postings to datsun-roadsters@autox.team.net
/// datsun-roadsters@autox.team.net mailing list
|