Me light is still glimmering!

[Medskipper]

Ok, a few weeks ago I asked why my battery indicator light was glimmering on. I got Lots of helpful advice, so many thanks to all those who helped me.

Now I have cleaned all terminals on wires from the alternator and to the offending light. I have checked the voltage output from the alternator, its charging at 14v. a few peeps suggested it was the exciter on the alternator, so took it off for a service, nice guy in T.A. Spares in Chatham says, well I can service it completely but that might cost up to £100. depending what he finds wrong, but says for £120. he can do an exchange for a brand new one! So I bit the bullit and got the new one, all fitted fine, charging fine and still my light is glimmering on!

WHAT ELSE CAN IT BE? HEEEELPPP !!! /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif

Barry

 

[savageseadog]

It will be your wiring or terminations. Check all your cables and crimps etc and your battery.

 

[paulm299]

How is your alternator driven ?

 

[orizaba]

try changing the bulb or checking wiring to bulb,can"t remember exact reason why it happens but the size/resistance of bulb makes a difference,maybe as it gets older resistance increases/decreases and so does not cut out properly,had this happen a while ago on a lorry and it cured it,there seems to be no real problem with your charging so i would say alternator ok,its worth a try

 

[alan17]

Make up a test lead incorporating a low wattage bulb. Connect one end of the lead direct to the battery and the other to the alternator exitation terminal.
Light will glow. Start engine and run at about 1500 rpm. If light still glows you have an alternator fault. If light goes out you have a wiring/connection fault.

 

[capnsensible]

Take the lamp out and hide it. This worked for me on various alarm systems on a variety of Submarines. It also means that when logging it, you can use the word 'spurious' with a straight face.

 

[OGITD]

Fwd "L" by any chance?

 

[Colvic Watson]

[ QUOTE ]
Take the lamp out and hide it

[/ QUOTE ] /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

 

[Medskipper]

I've just fitted a brand new alternator and it has not cured the fault!

Barry

 

[Medskipper]

Yes that what I have done already, can't find anymore connections to check! I think I will change the bulb though.

Barry

 

[capnsensible]

OA. Its more exciting with things that go bang. Translation, Ordnance Artificer, torpedo's, missiles and bullets.

 

[Medskipper]

Usual twin belt drive, all is fine with the drive of the alternator.

Barry

 

[misterg]

[ QUOTE ]
Make up a test lead incorporating a low wattage bulb. Connect one end of the lead direct to the battery and the other to the alternator exitation terminal.
Light will glow. Start engine and run at about 1500 rpm. If light still glows you have an alternator fault. If light goes out you have a wiring/connection fault.

[/ QUOTE ]

I second this suggestion - I think you (the OP) possibly have a (very) poor connection between the alternator and battery+. Do you have any charge splitting diodes, etc. or isolators in this circuit? If the wiring is OK, its possible that the fault could lie with these. (Alan17's test would tell for sure).

Andy

 

[VicS]

I agree with all the others who suggest that is a poor connection somewhere.

I had a similar "fault" on the car some years ago which turned out to be poor connection in a part of the circuit that supplied various auxilliary circuits including the warning light. Actually it was a poor connection to a fuse on that occasion but a poor contact on or within the ignition switch would have produced the same symptoms. Check all the connections from the battery through to the warning light wiring. A voltmeter is useful as a voltage drop along a section of wiring where there should be no voltage drop indicates resistance due to a poor connection. A digital meter on the 20volt range will do no harm or come to no harm if you connect it to something you did not intend to and is sensitive enough to show even a tiny fraction of a volt. You will be looking for rather more than that though.
It may be difficult to locate but while the alternator is operating normally and the battery is being charged there is no problem. Panic if the light comes on at full brilliance.

 

[savageseadog]

You probably won't be able to look for the type of bad connection I and others are suggesting you have with the equipment you're likely to have. Everything might look OK even to a normal ohms meter. What you can do with a digital voltmeter is to run the engine and put the meter at each end of the each cable connecting your charging circuit up, or preferably on the actual item that's supposed to be connected ie the battery terminal rather than the battery connector. You shouldn't see more than about 0.1V (100mV) on any connection. These measuremnts on a running engine with the leads and so on on can be quite dangerous because of all the moving machinery and belts etc so take care. Have you checked the battery?

 

[penultimate]

That dates you. (OEO in a previous incarnation.)

 

[mandlmaunder]

using fancy volt type meter check for minor short circuit/or bad earth connection within the system

 

[Marsupial]

on a car it can be caused by a high resistance in the ignition switch to the exciter. In other words by-pass the ignition switch and see if the problem goes away, if not look for corrosion at other termianals. That said I have seen this "fault" on diesel trucks when the batteries are fully charged - after running 8 hours with no stops with nothing electrical on. (drivers reported a glow around the watford gap having driven from scotland non stop.) - so it could be there is nothing wrong.

good luck

 

[RobinA]

Have you tried checking the earth on the light panel? I'm just thinking about lights on a car - if the earth goes you can end up with sidelights, brake lights and indicators all glimmering at the same time.

 

[VicS]

[ QUOTE ]
Have you tried checking the earth on the light panel?

[/ QUOTE ] It does not really apply in the case of the alternator warning light. It is not connected to the negative or earth. One side is connected to the "ignition" switch the other to the alternator (or at least the regulator). It lights initially when there is no output from the alternator and is in fact supplying the initial field current to get the alternator started. Once the output from the alternator has risen to the battery volts there is no PD across the bulb and therefore no current flow it goes out.

Very true what you say about dodgy earths on car light clusters though.