[TR] Suggestions for a voltage gauge replacment on TR4A

[TeriAnn J. Wakeman]

On 7/4/13 10:44 AM, Randall wrote:
>> I am considering replacing my amp guage with a voltage guage
> If the reason is that you are installing an alternator that exceeds the
> capacity of the stock ammeter; may I suggest keeping the ammeter and adding
> a shunt to recalibrate it?
You may, but I do not think it is the best solution.  This is one of 
those very rare instances where I have to disagree with Randall.  I 
believe that a voltmeter can tell you more about the health of your 
electrical system and if it is being overloaded than an ammeter can.

An ammeter will tell you if the current is flowing into the battery or 
out of the battery and how much.  The small car ammeters are mostly 
gross indicators and do not read small amounts of current flow well.

When I moved from Seattle to Monterey I drove my 1968 Land Rover along 
the coastal route.  It was a cold stormy trip down the coast. I had the 
headlamps on, the windscreen wipers on and the heater on high all day.  
The ammeter looked fine but next morning my battery was too low to start 
the engine and I needed to use the hand crank instead of the starter 
motor.  The electrical drain was just a little more than the generator 
could produce.  Not enough to cause a noticeable deflection in the 
ammeter but enough to slowly drain the battery.  A voltmeter would have 
caught the overloading right away.

A voltmeter will tell you when you generator/alternator is not healthy 
because the voltage will read lower.  It will catch worn brushes and 
overloaded circuits.  It can catch things like corroded poor connections 
that reduce the voltage in the system.

Right now the alternator is going out in my 1960 Land Rover.  The 
voltage is lower than normal but there is still enough to keep the 
battery charged.  I check the electrical connections because corroded 
connections can cause low voltage.  They are fine.  I'm keeping a close 
eye on the voltmeter to determine when I need to change the alternator.  
An ammeter would never catch this until the alternator completely 
failed.  If the alternator voltage drops another 2 volts it will not be 
able to keep the battery fully charged.  An ammeter would not catch a 
failure mode that doesn't quite keep the battery fully charged.

Both my Land Rover and my TR3 have Lucas voltmeters.  Last time I looked 
they were still available new.  With the TR3 I swapped the bezel ring 
and the curved lens from the ammeter to the voltmeter.

I would never go back to an ammeter again just because a voltmeter can 
tell you so much more about the health of your electrical system.

TeriAnn