I have put in a brand new battery and just come back from a drive. The
battery was not fully charged (probably standing for a while). However even
after driving for several miles, the pointer of the battery gauge is not
rising out of the red.
I assume the battery is not charging because the alternator may be weak.
However, my immediate concern is the fact that when the ignition is turned
off, the battery warning (ignition) light remains on. Yes, the key is out
but the light remains on. Any ideas why this is happening?
regards,
Kam Purewal
Midlands, UK
86 XJ12 Sov
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At 19:09 2002-04-03 +0100, Kam Purewal did say:
However, my immediate concern is the fact that when the ignition is turned
off, the battery warning (ignition) light remains on.
You’re talking about the red warning indicator with a lightning bolt
symbol? That isn’t the battery warning. It’s the charge warning.
Your alternator has a shorted diode, and it’s pulling current. Probably on
the order of four amps.
See my website and check “alternator diagnosis”. Whip out a DMM and
measure the AC on your car’s electrical system when the engine is running -
you should note an AC signal that SHOULD NOT be presentm but is because a
diode is shorted and your rectifier isn’t doing the full rectification job…
— http://jaguar.professional.org/
Sean Straw '88 Jaguar XJSC 5.3L V12 (LHD) ‘Black Cat’ 65K
Marin County, California '85 Jaguar XJS 5.3L V12 (LHD) ‘Bad Kitty’ 210K
'69 Buick GranSport 455 V8 324K
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Its the red warning indicator that looks like a battery and has - + inside
it. Its the ignition light that illuminates when the ignition is switched on
and goes out when the engine is running.
Mine goes out when the engine is running but comes on when the ignition is
switched off.
regards,
Kam Purewal
Midlands, UK
86 XJ12 Sov-----Original Message-----
From: owner-v12-engine@jag-lovers.org
[mailto:owner-v12-engine@jag-lovers.org]On Behalf Of Sean Straw
Sent: 03 April 2002 19:41
To: v12-engine@jag-lovers.org
Subject: Re: [v12-engine] Battery light on when ignition off
At 19:09 2002-04-03 +0100, Kam Purewal did say:
However, my immediate concern is the fact that when the ignition is turned
off, the battery warning (ignition) light remains on.
You’re talking about the red warning indicator with a lightning bolt
symbol? That isn’t the battery warning. It’s the charge warning.
Your alternator has a shorted diode, and it’s pulling current. Probably on
the order of four amps.
See my website and check “alternator diagnosis”. Whip out a DMM and
measure the AC on your car’s electrical system when the engine is running -
you should note an AC signal that SHOULD NOT be presentm but is because a
diode is shorted and your rectifier isn’t doing the full rectification
job…
— http://jaguar.professional.org/
Sean Straw '88 Jaguar XJSC 5.3L V12 (LHD) ‘Black Cat’ 65K
Marin County, California '85 Jaguar XJS 5.3L V12 (LHD) ‘Bad Kitty’ 210K
'69 Buick GranSport 455 V8 324K
-To unsubscribe go to
-To unsubscribe go to
At 20:53 2002-04-03 +0100, Kam Purewal did say:
Its the red warning indicator that looks like a battery and has - + inside
it. Its the ignition light that illuminates when the ignition is switched on
and goes out when the engine is running.
Odd, no reason for the battery voltage warning to light up (that’s what
that symbol is for on the XJ-S at least). Perhaps the XJ12 has a whole
different set of glyphs and meanings.
Mine goes out when the engine is running but comes on when the ignition is
switched off.
I’d still start with checking the alternator for an AC output, and/or
checking to determine exactly what sort of current draw you’re looking
at. You probably want to disconnect the battery or it’ll be flat in the
morning (if there’s much of a draw on it).
For future reference, there’s no need to copy the list AND the previous
poster - if you’re replying to the list, the people participating in the
thread will still get that copy.
— http://jaguar.professional.org/
Sean Straw '88 Jaguar XJSC 5.3L V12 (LHD) ‘Black Cat’ 65K
Marin County, California '85 Jaguar XJS 5.3L V12 (LHD) ‘Bad Kitty’ 210K
'69 Buick GranSport 455 V8 324K
-To unsubscribe go to
Just found a section in the haynes manual that says that if the light stays
on when the ignition is off, this is a sign of a faulty diode pack.
Thanks to all that replied.
regards,
Kam Purewal
Midlands, UK
86 XJ12 Sov
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