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Glyn Harper

Battery light on

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I recently fitted a recon alternator I got from the USA which is a straight swap for a standard one. Sure enough it went on fine. The main pulley was slightly larger so I had to go up one belt size (only a couple of cm longer)

When driving though, the red battery light is staying on, although not as bright as normal.

ive just driven about 20 miles, checked the battery, and it has 13.43v in it so I’m not sure exactly what’s going on to be honest.

I’ve checked the smaller wire is connected to the small terminal and it is. Any ideas?

If it wasn’t charging, would it have gone flat in the 20 miles or so I drove the car? I’m wondering if it’s the ecu giving an incorrect reading or something like that, as It’s possible my battery warning wire comes from the emerald m3d ecu I have. I can’t remember exactly as I fitted it about 18 years ago  :)

Any checks I can do?

 

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Just checked the bent tension which seems ok. But it’s definitely not charging. Ran the engine with amultimeter on the battery and watched it slowly going down. :(

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Stick the multimeter on the alternator output whilst idling.  What does it read?


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The big one.


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No, just probe the output.  Try and read it at idle and at approx. 3000RPM.


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Ok, it’s just that the big wire goes to the starter and then the battery so am I not just going to read that?

or do you mean to check if I’m getting a loss along the cables?

I was only seeing the battery level drop when I tested at the battery end, so yeah, I’ll check what I get directly at the alternator when I pull it out today. I need to the use it to go on a course today, typical! My daily driver is in having the bumper painted. :(

Edited by Glyn Harper

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While it's just a suggestion, and knowing that your alternator is brans new, I would still take the Liberty taking  a peek at the pick up points and see if they were touching coorrectly, as well as internal wires from those pick ups to the voltage regulator.

Just a suggestion.

Dead earth wire or point?

Kind regards,

jacques


Nobody does it better - than Lotus ;)

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You need to check the alternator output.  13.43v if engine not running is suspiciously high.  Your alternator may be overcharging, and this can cause the light to flicker.  You can check this by reading the alternator output directly at the output pole.

You say you got it from the States?  Maybe it's a left-hand drive alternator.

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British Ambassador to Florida, New York, Denmark and Newfoundland.  And Sweden.

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It is an alternator meant for the Esprit.

its only 13.3v when I’ve just taken it off the battery charger. It drops back to about 12.5 pretty quick after the charger comes off.

i tested it with the engine running at the alternator output and it was just going down from 12.5 which I’m pretty ire was just reading charge from the battery.

going to order another from SJ today. Pretty sure it’s faulty. I’ll see if I can get a refund. 

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Alternators work or don’t 


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Well, how about this for odd. I had to use the car today to go on a course, and all the way there it had the battery light on as it has been for the last few journeys.

I parked it up all day, but when I drove it home after being in the course for about 6 hours.. no battery light. I checked when I got home with a meter (engine still running) and it was showing 13.6v! I shut the engine off, and the battery was still at about 13.4v, so fully charged.

So somehow, it's mysteriously come back to life while it was say for 6 hours.. either that or it's just going to be intermittent from now on.

I'll leave the other one on order with SJ Sportscars anyway as I'm always going to be worried about it otherwise. But any idea what would cause it to do this? Most strange. As you say, they either work or they don't, normally.

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Check the earth to that alternator. Are you sure the mounting is tight


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I checked and tightened it all last night, and it was fitted with new bolts when I installed it in August, so it should be ok. I'll check though for sure.

It's weird how it wasn't charging this morning, then after being left alone all day worked perfectly on the way home.

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It earths through that mounting bolt - it’s critical it’s tight 


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This is odd. Tried the car again tonight and it wasn’t charging again. Ran a temporary Earth lead to check if it was a bad earth but that made no difference.

I decided to see if it really go flat so I put all the fans, lights and stuff on to draw as much load as possible. Then a few minutes later it started charging again fine!

as it’s not a genuine Lotus alternator, is it possible it’s some sort of intelligent system that only starts charging when the voltage drops below a certain amount?

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The alternator voltage regulator does just that - it senses voltage within pre-set limits and regulates accordingly. Around about 14 - 14.2 volts, I think, depending on the regulator.

If the previous alternator was working OK, then it suggests the new one is faulty in some way.


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I spoke to the company in the US I got the alternator from and they tell me they never have issues with the actual alternators, so they also suspect the regulator. I think it's somehow set too low, so it's only kicking in below 12.3v or something. Which is actually fine in a way, but I'd rather it right. So yeah, sounds like you're correct there Ian. :)

They're sending me another one to swap it.

I've also ordered a new plenum chamber gasket as I've worked out it's going to be easier to remove the plenum box to get to the regulator than remove and refit the alternator again to do it!

Edited by Glyn Harper

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16 hours ago, Glyn Harper said:

as it’s not a genuine Lotus alternator, is it possible it’s some sort of intelligent system that only starts charging when the voltage drops below a certain amount?

LOL

 

"Intelligent Charging System"????? 🤣

 

Maybe.  If you leave your headlamps on, they go out all by themselves, eventually. :sofa:

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Atwell Haines

'88 Esprit

Succasunna, NJ USA

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Ha ha!! I'm so used to the IBS intelligent battery system on my BMW. I think on a Lotus it's more a case of when all the bad earths occasionally manage to make some contact! 😂

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Glyn,

A new alternator with a new voltage regulator an dpick ups, will have to have the pick ups bed in to make them take the shape of the rolls inside the alternator.

Can you show a Picture of the alternator you bought and a closeup of the voltage regulator?

When my original voltage regulator melted it plastic on the rearside (towards the alternator itself), it dripped into the pickup points and the rolls the touch, preventing them from sending any voltage, or only a very low voltage, to the regulator, and then onwards.

Take a look here:

https://www.thelotusforums.com/forums/topic/67095-the-story-of-little-red-riding-hood/?page=15

Kind regards,

Jacques

 


Nobody does it better - than Lotus ;)

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