igniton light showing but alternator charging fine...?

[phatmendus]

hi, quick question as electrics are far from my strong point.

I have a plus two with an alternator. Over the past couple of days the ignition light has started to glow/come on even though the alternator is still charging which I have checked and confirmed. But the light isnt on all the time. it does the following:

when the ignition is on with the engine off it is on as it should be,

start the car and it goes off as it should and the charging begins, however as the engine revs increase i.e when driving, the light starts to glow red, this red then gets brighter if you apply a load such as the headlights, however I must stress that it is showing a charge as normal on the volt meter and at the battery. Now and then the redlight will go off when driving, so back to normal making me think its an earth prob or something.

I have checked the connections of the back of the alternator which seem fine, and as i say the indications are all normal before and on starting, and there is a charge as its running, the red light comes on just as the revs go up.

Any ideas on where to look or what it may be? Im hoping its a simple fix but would like an idea of where to start looking

thanks in advance.

Simon

[Higs]

Simon

The ignition light is fed by the brown/yellow wire from the alternator on one side and a wire from the ignition switch on the other.

When the engine is off, the ignition wire is at battery voltage and the alternator is at 0v - hence the bulb lights up.

When started, the alternator voltage should be the same as the ignition voltage (as they both come from the alternator). However, as the ignition wire goes from the ignition switch and the switch is fed from the alternator (either directly or possible through the old control box - depending on age and how it was converted) and the same wire feeds the lights, there are plenty of places that increased current could cause a voltage drop - and hence cause the light to glow.

To find the culprit, you need a voltmeter to see if where this voltage drop in. Work systematically from the alternator to the warning light measuring any voltage drop as the car is running and with head lights on etc.. i.e. start with alternator to ignition switch; then try across the ignition switch; then ignition switch to light.

Fiddly - but you will find the answer eventually.

Then it is a question of cleaning connections or possible changing the ignition switch depending on what you find.

Alternatively, learn to live with it!

Richard

[RogerFrench]

I'll add another opinion, having recently had the identical symptoms on my Europa TC. I think it's very probably the voltage regulator in the alternator.
Th "ignition" light comes on when battery voltage exceeds alternator voltage, or vice-versa. Your alternator may well be putting out too many volts. Check it with a voltmeter, and replace the regulator if so. Otherwise the alternator will start to fry itself, and other things if you're unlucky!

[phatmendus]

looks like I better get the voltmeter out. I measured the battery charge this morning with the car running, as well as the volt meter on the dash, and both seem to suggest the charging is as it should be. I suspect its a voltage drop somewhere along the ignition wire. I will have a look.

Thanks for the advise.

Simon

[peterako]

I second Roger's comments.

Had similar symptoms before Christmas which could have been the regulator. I brought it to my local 'Alternator etc.' shop and he reconed it was the regulator "But could be more".

I replaced the whole alternator 'just in case' and all's well since.

Not a difficult or expensive job.

I'd still check the the wiring as described by Higs......

Best of luck,
Peter

[billwill]

I've had those symptoms twice.

It has always been cured by fitting a new/refurbed alternator.


I'm 95% sure its a knackered regulator/diode pack in the alternator. You can replace just that bit if you can get hold of the spares, but its usually an indicator that it has been running too hot, so it's best to replace the alternator.

[Higs]

Simon

Billwill may well be right. If so, this would show up as a voltage drop between the small blade and either of the large blades on the alternator output block (when the engine is running).

I think you now have the two most likely options.

Richard

[bob_rich]

Hi Simon and others

Couple of things that might help. The voltmeter on the dashboard is quite a slow responding unit--response time into seconds I believe. the ignition warming light is quite quick is its response so if is flashes it may indictate intermittent charging but on average the voltmeter may indicate U R still OK and enough current is delivered to keep the electric load OK

I have had alternators have sticky brushes B 4 now. Brushes are much simpler than those on a dynamo that uses a comutating brush with full load current in them. The slip ring brushes in an alternator can wear down or jam with a few years of crud. They only pass a small current for the field but without this the alternator output falls off. I would check/clean brushes B chucking out and alternator or buying new bits

hope this helps

best of luck

Bob

[phatmendus]

Thanks for all your help everyone. Im going to try and solve the problem tomorrow.

cheers

Simon

[billwill]

Personally I would not try to clean up an alternator; there are whole factories devoted to doing that and they make them "as new" and they are not expensive.

You need to pay an extra deposit which you reclaim when you take the old alternator back to the shop.

[phatmendus]

one dead alternator. thought it was ok, but my brand new battery was fooling me with its good output...until that went dead!

got a new one on the way. ?35 +Vat +postage. not to bad I thought.

thanks for your help as ever. The timing of these electical gremlins are always spot on as I am sadly selling my car. Im about to put a post on the for sale page, if anyones interested let me know.

Thanks

Simon

[wobblyweb]

Hi Simon

Can you let me know where are you getting your new alternator from, ?35.00 sounds good. I need to replace mine for the same reasons as you.


Thank you

[phatmendus]

no probs. Link is below:

http://www.lukemotorsport.co.uk/


the guy i spoke with seemed very knowledgable and didnt want an exchange item etc. So ?35 plus vat, plus postage of ?8. Will hopefully recieve it tomorrow. I went for the 45 amp one rather than the 80, but if you want that one it was only slightly more expensive, but personally I would avoid it unless you know your loom can take it and you really need that extra output. 45 is plenty for the standard fit.

hope that helps

regards

Simon

[69S4]

Luke's 45 amp unit is what I fitted a couple of years ago and the price was about the same. Looked well screwed together and I've had no problems at all with it.

[bob_rich]

Hi

It looks like Simon is sorted now and like most car electrical problems it was not what it first appeared to be. regarding the alternator though , and depending upon the make, it is not a major strip down to clean up the brushes. On some cars ( certainly bit difficult on Elans though) it can be done in situ. I Have taken a couple of pics of a Lucas Alternator. After unplugging the leads 2 screws removes the cover and then the control module can be removed if that is suspect. But B 4 doing that 2 further screws removes the brush cover and control modules as an assembly and expose the field brushes. Just possible a quick clean of the crud and twang of the brushes might get some life back. worked for me a couple of times.

Anyway glad its fixed hope U find info useful

cheers

bob