Alternator or regulator?

whaleys · Post by **whaleys** » Sun Oct 12, 2008 5:25 pm

Hey guys,

When revs are above 4000ish the battery light starts to flicker, when above around 5000ish its on permanently. Drop down it goes off.

Is that the sign of the alternator on the way out? Not that I'm sure I'd be able to hear it but I dont think the belt is slipping...

Cheers,
Graeme

Mikie711 · Post by **Mikie711** » Sun Oct 12, 2008 6:57 pm

Mine did the same thing on the way home after buying it. Thought the belt was slipping but turned out to be a broken tensioner bracket. At low revs it was OK but higher up the alternator was moving about with the vibration.

robin · Post by **robin** » Mon Oct 13, 2008 8:57 am

Yes, worst case the m8 bolt that holds the bottom of the bracket to the block has sheared off flush with the block face - that's a right PITA to get out. Could also be broken wiring/loose electrical contact.

BUT whatever it is, get it sorted before you damage the regulator pack - if you're disconnecting the load whilst the alternator is running, you can break the regulator pack quite easily.

Cheers,
Robin

r055 · Post by **r055** » Mon Oct 13, 2008 9:44 am

Robin,
just out of curiousity, is the regulator pack part of the alternator assembly?

Only asking as my car is in the garage just now getting a new alternator under warranty as the last one was only 6 months.

Ross

whaleys · Post by **whaleys** » Mon Oct 13, 2008 10:07 am

Ali replaced the bracket as that had snapped and that was only 7 months ago so I would hope that its unlikely that it has gone again. I'll check the wiring, but never had this before, does the wiring deteriorate?

Could it just be the belt needs tightened?

Cheers guys for all the advice...

whaleys · Post by **whaleys** » Mon Oct 13, 2008 10:15 am

Also whats the best way to access the alternator, would it be through the rear wheel arch or removing the undertray? And if its not the bracket/belt and not the wiring, could it be the alternator or is it more of a case of its either dead or alive?

r055 · Post by **r055** » Mon Oct 13, 2008 11:15 am

mine is (was) giving me the symptoms that are opposite of what you are experiencing...
The battery light is on constantly and when i rev the arse out of it, the light flickers.

Mikie711 · Post by **Mikie711** » Mon Oct 13, 2008 1:35 pm

IIRC its easier to take the under tray off, but you can get to it if you take the rear wheel off and have an extra elbow joint !!. Even then its a pig to get at especially the top bolt. Check the tension first as a broken bracket or bolt will be pretty obvious then look at the wiring. Even with the correct tension this type of belt can still slip as the inner surface gets glazed but the usually squeal when they are that bad. Take it off and check for perishing. If all thats OK the probably the alternator to check it try this:

1. Set the Voltmeter to the DC scale and measure the voltage across the battery terminals - red lead of the voltmeter on the positive terminal, black on the negative. Make sure all the accessories on your car are turned off (lights, radio etc.) and then rev up the cars engine to a fast idle (say 2000-2500 rpm). You will need someone to rev the engine whilst you connect the meter to the battery. With the engine at a fast idle, the voltage on the meter should read around 14 volts (13.5 to 14.4). The alternator needs to generate a larger voltage than the battery's rated voltage to overcome the internal resistance of the battery. Turn on the blower fan for the AC or Heater, the headlamps, and any other accessories that put a strain on the alternator, and watch the meter to see if it decreases voltage. As a rule, if the voltmeter is higher when the engine is running then when the engine is not, you can confidently assume that the alternator is charging.
2. Listen to the alternator while the engine is running. If there is a problem with the bearings you may hear a squealing sound coming from the engine bay, which becomes louder with more electrical accessories using power at the same time.
3. Feel the alternator after the engine has run a few minutes and you turn the engine off. If it is very hot, you may have wear to the bearings or the insulation on the copper windings may be breaking down, an indication the part may fail soon. Bear in mind the Elise alternator is pretty close to the exhaust and will get warm anyway.

whaleys · Post by **whaleys** » Mon Oct 13, 2008 6:35 pm

Ok, did the voltmeter test and when everything is off it reads 12v sometimes flicking to 11.9v. When you start the car it drops slightly and at 2500 revs its at around 11.2v and rev it to 3000rpm and it drops to between 6.5 and 7.5v. All the while I dont think the battery light was on, wife was doing the reving and said that she couldnt be sure but didnt think it was as she was concentrating on keeping it at 2500

.

Now I am a total noobie with this but I'm guessing thats not too good.

Thoughts please, could this still be a wiring issue? (not had the chance to take things apart yet)

I take it its not a bad battery as its at 12v when everything is off.

Mikie711 · Post by **Mikie711** » Mon Oct 13, 2008 6:45 pm

Alternator is goosed. It should never drop below 13V when the car is running. At least you know whats wrong now. If it were a bad battery then you would still get between 13 and 14v when the car was running. Looks like your battery is OK and you need a new alternator.

whaleys · Post by **whaleys** » Mon Oct 13, 2008 7:04 pm

Why isnt the light coming on all the time then?

Went out and did it again and this time it stayed at a constant 11.5v at 2500 and 3000. But that still isnt 13-14v.

On that note, where would be the best/cheapest place to get a new one? I see that eliseparts do one but its £189 ex VAT.

Cheers,
Graeme

robin · Post by **robin** » Mon Oct 13, 2008 7:17 pm

Not sure where best to get one ... would ask at a motor factors as they'll probably be able to get one cheaper than a Lotus specific one. The alternators on S1 and S2 are different.

S1's are a bit more prone to wiring failure than S2, but it does happen to S2's also.

The wire from the dash light to the alternator serves two purposes: (1) to light the dash light when the alternator regulator output is less than some number (i.e. charge warning function) and (2) to tell the regulator pack that the ignition is on and that it should attempt to charge the battery.

If the wire breaks you lose both functions (top design, eh!) - the battery doesn't charge and the light doesn't come on.

When the ignition is on, engine stopped, the charge warning light should be lit. When you start the car it should go out. If it doesn't light when the ignition is on, engine stopped, then the circuit is goosed (probable wire break). If the light is on, then goes off when you start the engine, you have normal behaviour.

So, check the light is on when ignition is on, engine stopped before deciding to buy a new alternator.

Cheers,
Robin

whaleys · Post by **whaleys** » Mon Oct 13, 2008 7:54 pm

I am appreciating ALL the advice guys. I've been out and checked and the light does not come on when I switch on the ignition and the engine is stopped. All other lights do come on however.

I'm not sure to be relieved or more worried, is this problem likely to be more or less expensive?

Sorry as I am not sure where to start with electrics on cars but willing to learn

. Where should I start when trying to fix this? Could it be down to a fuse? Where should I start when trying to eliminate things?

Cheers

r055 · Post by **r055** » Mon Oct 13, 2008 8:12 pm

its definitely the alternator based on your multimeter readings.

get it over to a local auto electrician to confirm if your still in doubt.
you can pick up reconditioned alternators for much cheapness, but its a gamble

I got my car back tonight after a dodgy reconditioned alternator - was done free of charge but was a complete PITA

Ross

whaleys · Post by **whaleys** » Mon Oct 13, 2008 8:57 pm

Hi Ross,

Robin mentioned though that if the light is not coming on (mine isn't), there isn't a signal going to the regulator pack to tell it to charge the battery. Kinda not sure where to start, but would like to try and fix it myself. Any ideas?

Graeme

Scottish Elises

Alternator or regulator?

Alternator or regulator?

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