Ignition/Battery light on with ignition off

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Ignition/Battery light on with ignition off

Postby david.bradley » Mon 25.03.2019, 21:02

Hi
Looking for some advice please.
I was running car to charge battery and warm things through when I noticed battery volts at about 11v - always used to be 13-14V (ish)
When I switched off the battery light stayed on, it goes out when ignition turned on.
I've tried to research, and believe symptoms suggest a failed alternator diode pack. This is annoying as alternator is only a couple of years old, it was replaced by local garage.
I decided to do it myself this time, followed the guide, and alternator is off.
I've tried to test for failed diode pack and this is the plea for help.The diodes seem to check out OK. 0.995 in one direction and 0.692 in the other. I assume 0.995 is OK
Anyone any ideas what the problem is?, have I taken off unnecessarily?

Given that it's a pain to get alternator off I only want to do the job once.
I see alternator repair packs on eBay (Rectifier, Diodes, Brushes) at £40 - any thoughts?
All help appreciated
Thanks
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Re: Ignition/Battery light on with ignition off

Postby david.bradley » Mon 25.03.2019, 21:05

Sorry, wrong section
Moved to Engine ancilliares
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Re: Ignition/Battery light on with ignition off

Postby Rambo » Mon 25.03.2019, 21:12

El Geoffos, Saltire .... may be able to help you on this one ???

But, for what it's worth, your symptoms definitely sound like a goosed alternator to me
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Re: Ignition/Battery light on with ignition off

Postby GeoffSmith » Tue 26.03.2019, 00:29

Yep. Shagged alternator diode leaking via the warning light and back through whatever else is connected to the ignition supply in the instrument pack down to ground.

What units are the figures you quote David? If they're ohms (measured on the diode setting), they suggest a leaking diode.
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Re: Ignition/Battery light on with ignition off

Postby Saltire » Tue 26.03.2019, 08:16

:agree: I wouldn’t be happy with those figures, but it would be good to know the units of measure.

Does your multimeter - if you have one - have a diode check setting? Mine does, and it’s really useful in circs like these.

You might also find this YouTube link quite informative, and if you’re desperate, there’s a place in Wakefield called Auto Generators who do nothing but starter motors and alternators. I’m sure they’d give you a definitive view.

Hope this helps
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Re: Ignition/Battery light on with ignition off

Postby david.bradley » Tue 26.03.2019, 20:28

Thanks as ever for the help.

My multimeter does have a diode setting, and those are the results.
I cant claim to understand fully, but I think the measurements .are millivolts, that the multimeter pushes out to test what gets through the diode(s).
One direction it's zero, and the other 0.690mV.
From what I'd seen on Youtube I think it's the sign of diodes being OK - which is why I've lost my confidence. Up to that point I'd read that light on/ignition off was classic diode pack failure.

I think I'm going to buy a used genuine Lotus one......the one that's failed was an aftermarket item.
How important is the capacitor?, the one I've seen for sale has a damaged capacitor and I don't want to swap anything from the faulty unit.

Thanks again, much appreciated
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Re: Ignition/Battery light on with ignition off

Postby Saltire » Wed 27.03.2019, 08:54

David, I wouldn’t buy one that says it has a damaged capacitor unless you’re planning to refurbish it anyway. Without going into huge detail, a capacitor-assisted alternator won’t work properly if the capacitor is faulty. If I were in your position, I’d take my existing alternator to a decent specialist, and get it properly checked. If it’s fine, we’ll need to look elsewhere for the problem. If it’s faulty, they may be able to rebuild relatively cheaply and if they can’t, then’s the time to spend big bucks on a new one.

We have a specialist down here in Gloucestershire that offers a two day turnaround on a rebuild for about £50, and they’ll give you an estimate first. As you have the alternator off the car anyway, I’d be tempted to explore that with a local supplier to you.
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Re: Ignition/Battery light on with ignition off

Postby GeoffSmith » Wed 27.03.2019, 11:34

Over the years there have been many cases where people have had an alternator repaired, or bought a refurbished one which has died shortly after fitting. Because of the position of the alternator, it is likely to get very hot at standstill. I am certain that the cheaper repair kits only have parts which are rated at a (comparatively) low upper temperature which is probably fine for most other cars. In general…

Commercial: 0 to +70°C
Industrial: -40 to +100°C
Military: -55 to +125°C

I would ask for confirmation of the temperature specification of any replacement parts.
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