Battery light on but alternator working fine
Discussion
Hi the battery light came on the other day although the volts were fine (lights on too) and that was confirmed with a voltmeter on the battery terminals.
Alternator swapped and the same results. It's not the fan belt either.
I vaguely recall something like this happening before and it was a fuse or something connecting to a related circuit, but can't remember what, will have to do a search.
Alternator swapped and the same results. It's not the fan belt either.
I vaguely recall something like this happening before and it was a fuse or something connecting to a related circuit, but can't remember what, will have to do a search.
Hi Adam
My battery light kept coming on but only briefly and was pretty vague....However over a period of a couple of months it started to come on more often and was brighter...I had the alternator checked and it was borderline ...My volt gauge was showing 11-13v....Since I have changed the alternator the light has gone and the volts are up to showing just under 15v...
Try cleaning the contacts....
Ziga
My battery light kept coming on but only briefly and was pretty vague....However over a period of a couple of months it started to come on more often and was brighter...I had the alternator checked and it was borderline ...My volt gauge was showing 11-13v....Since I have changed the alternator the light has gone and the volts are up to showing just under 15v...
Try cleaning the contacts....
Ziga
adam quantrill said:
Yeah this is full on irrespective of engine speed.
You mentioned a fuse in your OP, the warning light will come on at full brightness if the fuse that powers the Alternator warning light blows or the wiring somewhere between the fuse and the warning light goes open circuit or the fuse is ok but loses the supply to it. Any of the previous mentioned faults will also prevent the warning light coming on when switching the ignition on, the light will only show once the engine has been started and high revved for the Alternator to cut in. The Alternator cut-in speed is increased if there is no warning light on when in the ignition positionAnother possible cause is the warning light wire from cluster to Alternator shorting to earth but when this happens the short will often blow the diodes in the alternator unless the wire has become detached from the Alternator and is shorting to earth
Is the warning light coming on as it should with ignition on and no engine running ?
Charging light is battery backed.
In other words it has 12v sitting behind it.....so when there is nothing on the field coils of the alt it will glow, as the Alt starts to turn the volt will increase and reduce the glow. Once alt is at normal speed it will also show 12v
So...with 12v both sides of the bulb there will be no current flow and bulb will not glow.
Check back of bulb for 12v on both wires, one is obviously ground, as its on all the time.
I would guess it's the one from the field coil not the dashboard one.
In other words it has 12v sitting behind it.....so when there is nothing on the field coils of the alt it will glow, as the Alt starts to turn the volt will increase and reduce the glow. Once alt is at normal speed it will also show 12v
So...with 12v both sides of the bulb there will be no current flow and bulb will not glow.
Check back of bulb for 12v on both wires, one is obviously ground, as its on all the time.
I would guess it's the one from the field coil not the dashboard one.
Yeah it does.
Full symptoms are:
ignition off - light is off, battery does not go flat overnight.
ignition on - light comes on
cranking - light goes off
running - light comes on
turn off ignition - light goes off quite rapidly
The fault I was thinking about on the other car was to do with the full beam somehow - as I recall the full beam warning light was lit dimly. In this case, it isn't.
I don't think there's any fuse in the alternator circuit at all, on a wedge. Battery side or field side.
Full symptoms are:
ignition off - light is off, battery does not go flat overnight.
ignition on - light comes on
cranking - light goes off
running - light comes on
turn off ignition - light goes off quite rapidly
The fault I was thinking about on the other car was to do with the full beam somehow - as I recall the full beam warning light was lit dimly. In this case, it isn't.
I don't think there's any fuse in the alternator circuit at all, on a wedge. Battery side or field side.
Do you have this, taken from here https://www.pistonheads.com/gassing/topic.asp?h=0&...
http://thumbsnap.com/f/zR3QcnKD
If you crank the engine over a little without starting it so as to turn the Alternator a touch at a time, is there a loss of warning light dependant on the position of where the pulley has been rotated to? This would mean the brushes aren't always contacting the slip ring, the thing is the light should then be less than full brightness when it's on with the engine running
The above diagram shows fuse 13 for the warning light and gauges
http://thumbsnap.com/f/zR3QcnKD
If you crank the engine over a little without starting it so as to turn the Alternator a touch at a time, is there a loss of warning light dependant on the position of where the pulley has been rotated to? This would mean the brushes aren't always contacting the slip ring, the thing is the light should then be less than full brightness when it's on with the engine running
The above diagram shows fuse 13 for the warning light and gauges
Edited by Penelope Stoppedit on Monday 27th November 20:15
You are right though it might have been fuse 13 previously, and there's a path through the main beam warning lamp for the alternator field to get a bit of juice, so it glows dim.
Having said that, that was a different car and maybe this one would present a different symptom, so worth checking the fuse.
Having said that, that was a different car and maybe this one would present a different symptom, so worth checking the fuse.
Edited by adam quantrill on Monday 27th November 21:03
It's interesting that TVR have wired the main beam warning light in such a way that if the bulb or bulb holder went short circuit the gauges/warning lights Fuse 13 would blow and the Alternator warning light would stay on at full brightness when main beam was switched on
There is also the possibility that if Fuse 13 blows the Alternator warning light will be getting on glowing brightly as it will be supplying the gauges
Very interesting
There is also the possibility that if Fuse 13 blows the Alternator warning light will be getting on glowing brightly as it will be supplying the gauges
Very interesting
Update on this - I had a brainwave when replying to the other alternator post...
I hadn't connected up the correct "sense" post on the new alternator, connected it up just now after removing my "blade" adapter (the other alternator had blade connectors for the sense connector).
Normal service is now resumed, charging at 14.4V. Battery topped up too.
I hadn't connected up the correct "sense" post on the new alternator, connected it up just now after removing my "blade" adapter (the other alternator had blade connectors for the sense connector).
Normal service is now resumed, charging at 14.4V. Battery topped up too.
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