Battery light

[jimbo]

Got my faulty battery swapped by dingbro today, and bruised knuckles later it's in and fired up.

but now the dash battery light doesn't go off...

Please tell me this isn't an alternator problem

James

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[robin]

This is an alternator problem or you've blown a fuse. Will post up what to check later.

[robin]

The alternator charge warning light works from the alternator. For so long as the wire is connected (a common fault is the wire connector fracturing and thus the wire becomes disconnected) then the light will be lit if alternator output is below a certain voltage. Now that can be because the alternator regulator is broken, the alternator isn't turning ... I assume you've checked the belt? ... or the alternator has no current from the battery to energize the field coil. The latter can happen either because the fusible link has bust or because the wire has fractured on the back of the alternator.

Of all these, the most likely is that the alternator regulator pack has self destructed.

So:

With ignition off, keys in pocket (safety first!), locate the thick wire on the back of the alternator. Using either a test lamp or a multimeter check that it's at +12v ish. You can find the other end of the same wire on the back of the starter if you want to test your test lamp/multimeter is working.

Check belt is hooked up.

Start engine and check alternator spins while engine is running.

Check voltage at battery while ignition is on with both engine stalled and engine running. If it's higher whilst engine is running alternator is doing something; chances are it will be lower given charge warning light is on.




If the thick cable at the back of the alt is not at +12 then the fusible link has gone - you need a new wire (it's part of the wire, I believe). Never seen this happen but have heard reports from others.

If the belt is off or loose you probably need a new belt and you probably need to check the M8 bolt that holds the alt bracket near the crank pulley - they have a habit of working loose and then breaking off in the block. Seen this happen with monotonous regularity.

If the belt looks like it should work but the alt isn't turning, it's perhaps seized (does happen, I think).

If all of the above is OK, the alternator is gubbed or the wiring at the back of the alternator needs attention. Very common problem. Buy a proper replacement.

Cheers,
Robin

[jimbo]

Think brother has a multimeter so will borrow that.

I'll have a bash at working through that list (think I understand most of it!) thanks robin

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[jimbo]

Car is booked into Taylors auto electricians next Tuesday, for testing the alternator wiring and replacing if needed. Belt was fine, and was showing lower voltage at the battery with engine running. Hopefully just the wiring, cause just seen that a replacement alternator from Elise parts is the guts of £200!

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[robin]

I'm sure EliseParts product is OK but I would ask Craig at MMC what price an alternator is from them ... there is certainly some difference in the quality of non-OEM alternators.

Cheers,
Robin

[jimbo]

Will do

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[jimbo]

Finally got the motor back, shiny new alternator fitted. Taylor's Auto in Aberdeen all but said if they never see the car again it'll be too soon. Charmed they were not...

Bill a bit on the high side, but just soooo happy to have her back!

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[robin]

They obviously hadn't fitted an alternator to an elise before ... easy when you know how ... hard when you don't

Anyway, glad it's all back and fingers crossed everything stays working for the summer!

Cheers,
Robin