Battery light glowing

[the invisible dog]

Yay, Big Red is back on the road after the thieving <edit> tried to take him away
All has been going well and I am looking to rewire all the lights, etc. ASAP
The other day on the way home I noticed the battery light in the warning light bank was glowing dimly
On first ignition stop it comes on bright as usual
Start the engine and it still glows bright, but it has always done this
Pull away or rev the engine and normally it would go out but now it drops to a steady glow  :?
This does not vary greatly with revs and no other oddities are apparent
Voltmeter is showing normal level while running and my CB's internal voltage readout across the battery shows a good 13.8V
My thoughts are towards iffy connections after the work to repair the damage but would expect something more intermittent to show
Alternator is fairly new and output appears to be OK from readings
Looking at the circuit diagrams I see the diode and resistor involved with this warning light - could these be kaput and where the 'eck are they?
Duff bulb?
Dodgy battery?
Anyone else seen similar?
Any thoughts much appreciated...  ;)

[Boddle]

Had a similar thing in the past the cause is usually a voltage differential between the Battery and alternator

when you start the engine the power to feed the coil in the alternator comes from the battery across the light once the alternator in able to power itself it the voltage at battery and coil is equal and the light goes out. The light circuit isn't switch its just easier for power to come from the alternator than battery.

 what you will find is that some where between the battery, ignition switch or bulb there is a drop in voltage say from your charging 13.8 to 12 (the brighter the bigger the drop) and your alternator is feeding power across the charge warning light backwards.
 
 The problem you have is finding out where in your electrics you leaking power to drop the voltage.

 You could replace the bulb with LEDs unit which will only let power through 1 way.
http://www.ultraleds.co.uk/ do a lot of LED replacement bulbs.

 This does solve the root couse of the problem

[mark.yellow.series.3]

i think you'll find you alternator is on its way out.
what is accually happening, is the brushes are losing contact with the slip rings inside the alternator. if you are a bit technically minded you can fix it your self.
take the back off the alternator to reveal the regulator which the brushes are part of. remove the screws that retain the regulator and remove it, check how much brush is left, it might be that the brushes are worn down to nothing and you will need to buy a regulator/brush pack (about £15-20). or it might be that the slip rings are dirty, if they look black, you need to clean them up with some emary paper.

mark

[tonycougar]

Mine was doing exactly the same. It turned out it was the brushes on the alternator, they were stuck in and and not making a good contact with the slip ring. Eventually the light came on permanently, causing me to take the alternator to bits and find the snag.

[the invisible dog]

Thanks guys,  ;)

Definitely food for thought, now to start digging...
Alternator has actually done very few miles since new so will be miffed if it is 'on its way out' but it has also been standing for a few months so wouldn't be hugely surpised if something has stuck
It was OK for a short while after getting back on the road so could be the brushes, etc. have just worn to 'that point'
The constant glow of the bulb and the 13.8V reading make me think down Tony's line tho'  :?
WOuld the output not be low if the alternator was the problem?
Also, most of the attempted theft damage was wiring behind the binnacle
Neither alley is particiularily tricky to follow so maybe I'll toss a coin and then dive in  :lol:

Will let you know how it goes  :roll:

[mark.yellow.series.3]

good luck

[minty]

same as all above just last week had the same problem with the wifes disco mk1 x2 alternators and x1 battery and an auto electrican later problem solved alternator was nakkerd even the supposed new one had to be replaced  but all good now

[Steve ray]

Reckon its the regulator on the alternator - it would appear that its on its way out