Hi Pat and list,
as a rule of thumb, you should use a fuseable link or maxi fuse equal
to or less than the output rating of the alternator, in series with
the alternator output lead.
This will protect the alternator from overloading.
A proviso here is that the alternator wiring is of a suitable gauge to
handle the alternator output.
Remember the fuse in any circuit is there to protect the wiring from
overload.
The ammeter monitors the charge/discharge current of the
battery/alternator system.
If, for example, the ammeter reads +30A to -30A as my '65 SP310 does,
you can fit another maxi fuse (30A) in series with either of the
ammeter wires to protect the gauge from being subject to currents in
either direction of >30A.
Unless there is a fault condition, an automotive ammeter, when the
engine is running, should spend most of its time on a few amps
charge(+) with an occasional momentary flick to discharge (-) when
loads are switched in, then a return to the charge state.
High current indication in either direction with the engine running is
not normal.
A flat battery will suck a lot of current but with everything else
being equal, draw should be in the order of 3-5A
On a gauge calibrated to read 30A, this is simply a needle leaning
towards the + side of the centre position.
Hope this helps you understand the method of dimensioning fuse
protection.
Regards,
Graeme Suckling
1965 SP310 - under construction DSOA Member # 112
1971 P510 4 door - daily driver, original owner, highly modified.
1972 PL510 2 door - in storage.
1973 HS30/240Z - re-building to 2003 specs.
http://www.imagestation.com/album/?id=4290669159
Adelaide, South Australia.
-----Original Message-----
From: owner-datsun-roadsters@autox.team.net
[mailto:owner-datsun-roadsters@autox.team.net]On Behalf Of Pat Mahoney
Sent: Tuesday, 26 August 2003 12:22 PM
To: datsun-roadsters@autox.team.net
Subject: ampmeter test
Boy I'm getting close to the first run. I want to try to prevent some
of
the typical problems in advance. How do I check my ampmeter? I
understand
that some listers suggest fusing in front of the gauge. What amp fuse
is
best? If all goes well, I'll enjoy a Labor Day Weekend road trip.
Thanks
for your help. Pat Mahoney '69 2000x21/2
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