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Re: Voltage Regulator Blues

To: <mg-t@autox.team.net>
Subject: Re: Voltage Regulator Blues
From: "Bob D." <bobmgtd@insightbb.com>
Date: Wed, 24 Apr 2002 23:26:40 -0500
Whoa, .2 amp (or 200 mA) is an unacceptable amount of "standby" current.
That much current would easily deplete the battery in a week or so. There
are many devices in the modern car (mostly computer) that draw some current
with the ignition off, but manufactures try to keep the total current under
5 mA (.005 amp). Even this small amount is a stretch for storage over an
entire season. The auto makers design around a two week period in an airport
parking lot. (For some reason auto makers think cars are never idle except
at airports.)

Our old MGs shouldn't have any draw except the clock (if you're lucky enough
to have a clock that runs). I don't know what the old mechanical clocks
draw, but it should average a lot less than 200 mA. (It probably draws it's
current in occasional pulses.) My clockless TD draws absolutely no current
with the ignition off. I never disconnect the battery or charge it during
it's winter slumber. But, there has always been plenty of charge left to
start it in the spring. (There's usually a couple breaks in out Indiana
winter weather when I can get it on the road, so my real max storage time is
probably 2 months.)

If you can measure the battery's current drain, I suggest disconnecting
circuits one at a time until you see the current drop. Start by pulling the
fuses, as these are easy to remove. This should help pin point where the
leakage is.

Bob Donahue (Still stuck in the '50s)
Email - bobmgtd@insightbb.com
52 MGTD - NEMGTR #11470
71 MGB - NAMGBR #7-3336
.
----- Original Message -----
From: "Scott Allen" <scottinarl@hotmail.com>
To: <mg-t@autox.team.net>
Sent: Wednesday, April 24, 2002 11:50 AM
Subject: Voltage Regulator Blues


> Hi,
>
> As some of y'all may remember I had a problem with the volt. regulator on
my
> TD back in November.  At the time I had replaced it because my battery was
> dying, and testing indicated the old one was drawing current when the car
> wasn't running, or rather it was determined that the points in the reg
> weren't operating properly.  Replacing it fixed the problem.
>
> So I try and fire up the TD last PM, (five months and 800 miles later) and
> the battery's dead.  Testing today at indicates the charging system's
> behaving as follows:
>
> RPM           Volts @ Generator & Battery     Ammeter Reading
>
> 1200, (idle)          12.06                      -1 or so
>
> 2000                  13                         10-15
>
> 2500                  13.5                       15-22
>
> When the car's shut down I have a miniscule draw, (.2- of an amp) which I
> think is probably the quartz movement in the clock.
>
> Oh yeah, I have the 5-post reg..
>
> So I'm wondering if the above is "normal" and if so maybe I'm dealing with
> the transient open points issue again, which considering that both regs
came
> from the same source may be a possibility.
>
> Any info appreciated,
>
> Scott Allen
> 52 TD
> 74 1/2 BGT

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