alternator not charging - (tacho draining voltage) FIXED

[mudguard]

More information - voltages across battery:

at rest = 12.68

ignition on = 12.38 (then up to 12.44 as fuel pump stops priming)

cranking = 9.8

started = fluctuates continuously between 11.7, 12.68, 14.02. Tacho light stays on constantly. Remove exciter connection, exact same readings.

Voltage on yellow/brown at alternator, ignition on but not running = 10.2

If the voltage readings whilst running are to be believed, this suggests that the alternator is kicking out something. But is it enough to charge the battery? 

Perhaps I should try running it with the belt removed.

It's starting to feel like an alternator failure to me. Have I got this right?

[Jonathan Kay]

Mmmm... data!

...

What sort of alternator and how many wires connected? Any recent relevant work?

The plug with the yellow+brown wire is intact and sound.

Wires look OK, not cooked and connections feel right on wiggling? 

Also check how the alternator is earthed... probably through the engine, and then check all those wires and connections.

...

With intact wiring and connections and a good belt at the right tension those fluctuating alternator output voltages do sound like a fault inside the alternator. They are surprisingly repairable and I'd start looking for where to have that done.

Jonathan

 

[Jonathan Kay]

cranking = 9.8

That's a bit low and some electronic bits on some 7s will drop out. But I don't think that's got much to do with your current problem and would come back to it later, with one exception: is your battery the type that allows topping-up and does it need it?

Jonathan

[Jonathan Kay]

So I think the next step is to determine whether it's the insufficient-exciter-current problem or the failed-alternator problem. So I'd like to run a temporary test wire from the battery +ve to the yellow+brown at the alternator. 

Do you understand that circuit and how an incandescant bulb traditionally provides the required resistance? See #22.

But - newbie question - how do I physically achieve that temporary connection at the alternator end? Preferably without damaging the loom? 

Can you add a photo of the alternator connections with and without the plug in place?

Jonathan

[revilla]

1.8 VVC SV on Toyos? Sounds familiar (he says, looking in his own garage ). I'm guessing as you talk about the plug with the brown and yellow wireless that it's also EU3? I'd be inclined to agree with Jonathan on this, sounds like your alternator has just packed in. You shouldn't be seeing the voltage fluctuating like that. Poor excitation is more likely to just show up as a reluctance to get going when you first start. Very unlikely that your alternator isn't earthed properly, it's bolted to the block and that is earthed through long the same wire to the battery as is used when cranking the engine, so if it will take the starter current it will be fine. I really wouldn't advise people to be shorting the lamp wire across to the battery to test this; if you're going to try it, at least put a small bulb (I've used 2W and 4W before, e.g. WOSP advised 3W and no more than 5W above) in the line to limit the current. If you've got the two pin sealed connector on the back of the alternator with the lamp and DFM connections, you could unplug this and carefully push a little female terminal onto the pin (it won't cause any problems testing it with the DFM disconnected) or you could carefully slip a metal pin into the back of the plug, slipping it past the wire seal to contact the terminal, but both of these need care and you risk doing damage; I would honestly just get the alternator checked out first.

[mudguard]

Thanks Jonathan and Andrew, it is indeed an EU3. It's run fine for hundreds of miles since the last piece of work, when Mr. Belcher renewed the alternator belt at the same time as the cambelts. The belt turns fine with no judder and the pulley's not slipping, so I'd be amazed if this problem was anything to do with the belt change. Connections look tight - I also have some kind of indication that they're making since with the alternator plug removed the tacho LED does not light - only lights when plugged, and then never extinguishes.

I'm happy to conclude the alternator has packed up due to old age and just go from there either repair or replace depending on timescales / costs.

So, next question, how do Ioosen that pesky rear bolt to remove it? Primaries are in the way and I can't even seem to slip the socket over it, let alone get the extender bar connected to it. I'll have another go later when it's not raining. It is even possible to remove the thing without removing the primaries?

Ideally I'd prefer not to drive it to my friendly local seven specialist (35 mins, 11 miles) owing to the increased risk of needing recovery. Although I can fully charge the battery from the mains, and the voltage measurements above suggest a low current draw when running. Obviously headlights/fans/heated screen would be best avoided!

And I think undoing 3 bolts should be within my spannering capabilities....

[mudguard]

After puzzling over why nobody else in the entire internet has had a problem removing the "rear nut" I was struggling to access, I eventually stumbled across this very useful picture

https://rimmerbros.com/Item--i-GRID003168

which explains what mr numpty here should have figured out - it's not a nut, but the head of a through-bolt which attaches with the front nut, and you just push it out from the front having removed that nut. Duh.

That leaves only the charge lead nut blocked by the primaries. To get that off I just wiggled the alternator to a different position to allow socket access.

[Jonathan Kay]

:-)

One of the advantages of repair over replacement is the certainty that it will fit!

Jonathan

[mcerbm]

Ok just finished testing. The original wiring from the tacho showed 7.8V at the alternator. So there is definitely something up with the tacho and the LED inside. I wired up a LED to a 12V igintion switched live and placed in the dash then used the original wiring from the bulb to the alternator. Hey presto! 10.7V engine off, about 0.6V when running and alternator charging and dash light off.

Thanks everyone! bodged wiring now removed.

[revilla]

Just for reference, do you know the voltage and current ratings of the LED you used?

[mcerbm]

Revival, unfortunately not. It was in my spares box for a few years. It doesn’t have any markings other than 12V LED. 

[Jonathan Kay]

I'll think about where to put this for future reference.

Jonathan

...

https://www.lotus7.club/forum/techtalk/alternator-not-charging-tacho-draining-voltage#comment-2248141
 
Dear WOSP
 
There seems to be inconsistent information about the connections on the LMA226 in your literature. The issue is described in the link above.
 
Your advice would be greatly appreciated.

...

Dear Jonathan,

Historically we always supplied the unit with 3 x additional connections on top of the M6 B+ charge stud:

Ig - Ignition, switched 12v feed to excite / turn on the alternator.
S - Sense, constant 12v reference to battery +ve but linking to the M6 B+ stud is sufficient.
L - Lamp, not essential but indicates if there is a problem or the belt snaps etc.

In recent years we have updated the spec to improve the ease of fitment:

Lamp - whereby the sense is no longer required and the switched ignition and lamp pin have been combined. It therefore now only requires the same 2 x connections as the original S1 Elise alternator.

The LMA226 has however now been discontinued by us as the OE Denso platform in no longer available new OE from Denso and the Chinese made aftermarket equivalents are not fit for purpose. We have therefore now developed a 95A unit with CNC'd billet casing and the same two B+ & Lamp wires. It's part number is LMA321.

Kind Regards
Luke

---
Bespoke Starting & Charging Systems
O.E. Quality, No Compromise.

WOSPERFORMANCE LTD
UK.
E - info@wosperformance.co.uk
www.wosperformance.co.uk

 

 

[mudguard]

Andrew and Jonathan - your diagnosis was a bullseye - thanks.

I bought a "Bosch 467 genuine reconditioned" alternator from a company called Schmitz Rotary Engineering. It arrived today, complete with printed measurement report, and is now on the car. I now get a steady 14.5v across the battery at any revs.

Over the weekend I opened up the old unit to try to spot the problem - everything looked fine, no burnt windings or broken connections; resistance of the windings as expected, fair length left still in the spring-loaded stator brushes. I can only conclude that the voltage regulator has packed up. These are a sealed replace-rather-than-repair plug-in module and incorporate the brushes for the stator, and are readily available.

I could have saved half the price by replacing only this, but having compared the reconditioned alternator with the old I'm glad I spent the extra. It turns far more easily and is much quieter. It looks like the reconditioning job was excellent.

So happy to be facing the prospect of going out in the Seven again!

[Jonathan Kay]

:-)

Thanks for telling us the outcome.

Jonathan

[revilla]

Good news. Glad to hear it is fixed.