[TR] Battery Drain

[spamiam at comcast.net]

Sam,

It takes a fair amount of current to light up a test light.  How fast does 
your battery drain to flat?

As usual, Randall is correct that the test light illuminating for a short 
time then going dark does suggest charging of a capacitor.  And it is a 
pretty big one!  Lets say that it takes 50mA to light your lamp, and it 
lights for about 1/2 second.  That equates to 0.1 coulomb.  in capacitance, 
this is 0.1 coulomb/12v = 8333 microfarads.  A reasonably large capacitor.

So, it may be the "unseen" drain, the one that is not enough to illuminate 
the test lamp, that is killing your battery.  When I had this problem, I 
placed an ammeter between a battery lead and the battery (engine not 
running), then pulled fuses until it dropped to zero.  From there I traced 
it further down the line until I got the individual device.

In one case, with my 1966 TR4A, pulling all the fuses changed nothing.  I 
eventually got the the mechanical regulator as the source of a drain of 10's 
of mA.  I blew all the dust out of the device especially in the back and 
from between the contacts.  That fixed it.  I did not do more that pull all 
the leads, and blow a jet of air throughout!  You don't have such a 
regulator, but I suppose a fault in your alternator's regulator could do it.

You can hook up the ammeter, measure the mA of drain, then remove the ign 
warning light lead (if present), and see if the mA changes.  If it does not 
drop to about 1mA (which may be about normal), then remove the main lead 
from the alternator either at the alternator, or at the other end of that 
big lead.

-Tony

-----Original Message----- 
Message: 3
Date: Fri, 28 Jan 2011 21:38:11 EST
From: TRDOCTOR at aol.com
Subject: [TR] Battery Drain
To: triumphs at autox.team.net, 6-pack at autox.com
Cc: tr6 at atlasok.com
Message-ID: <98078.975db8b.3a74d793 at aol.com>
Content-Type: text/plain; charset="US-ASCII"

My '72 GT6 seems to have a slow drain on the battery.  When hooking up  the
battery there is a small spark.  When using a test lamp that is  grounded,
it lights up slightly and then goes out.  Have checked with all  of the
fusible circuits and it doesn't show up.  Could it be a bad diode in  the
alternator?
Suggestions?

TIA
Sam Clark
Green Country Triumphs