battery light / alternator?

[S3 rich]

just a quickie, on start up i have always had the battery light on until i blip the throttle or take it to about 2k revs, dependant on the weather strangly enough? rhis then seems to wake up the alternator.

not really been too bothered about it but recently getting slightly worse, sometimes.

any ideas? is it looking like the alternator is on its way out or something else?

my mates sunbeam alpine has just started doing it aswell....

voltmeter applied to both, all is well once awoken.

ps looking at the photos in the forum its nice to see i dint have the dirtiest S around!!

Richard.

[oldred]

S3 rich said:

just a quickie, on start up i have always had the battery light on until i blip the throttle or take it to about 2k revs, dependant on the weather strangly enough? rhis then seems to wake up the alternator. not really been too bothered about it but recently getting slightly worse, sometimes. any ideas? is it looking like the alternator is on its way out or something else? my mates sunbeam alpine has just started doing it aswell.... voltmeter applied to both, all is well once awoken. ps looking at the photos in the forum its nice to see i dint have the dirtiest S around!! Richard.

I believe this is normal for the S2/S3 IIRC from the S Bible

>> Edited by oldred on Wednesday 8th December 08:42

[tvrgit]

Yep this is normal. Don't worry unless the light DOESN'T go out at 2,000 revs.

[S3 rich]

on the odd occasion it will take 3-4k before it goes out, but not very often maybe every month or so, which isnt very often as i use the car every day.

[Hoover33]

Yep light stays on until 2000 revs is the norm

[NickP_S2]

I recently had fun and games with this while travelling. I noticed that the voltage was steadily dropping. Unfortunately I was travelling at night (lights / wipers on). The voltage dropped until eventually the car died.

My initial thought was that I needed a new alternator as I thought that it was the most likely cause of a whirring noise I'd been hearing for some time. I managed to charge my battery after getting help to reach my destination from the person I was travelling to see.

It wasn't until I turned the ignition on with the freshly charged battery that I noticed that the battery warning light hadn't come on. I wiggled the wires that go to the warning lamps under the dash and hey presto - the battery warning light came on.

Gave the throttle a blip - voltage went up and not had a problem since....

Seems a little silly that the alternator should fail if the battery warning lamp isn't working...

[nawarne]

Gents,
This is down to getting enough 'power' (V X I = Watts) to excite the stator windings on the alternator.
If the battery is a little tired, and I suggest it would be this time of year with lights, heater blower (my heater fan really drops the voltmeter) on, then it can be a while before there are enough volts and amps 'circulating' after the heavy knock of turning over a biggish engine on the starter.
So, whilst the alternator is rotating it just takes a while for the field coils to energise before it starts putting out.
As you say, in the summer, with the battery getting loads of juice when you're driving the alternator excites more quickly.

[F908 TIM]

Yep,my heater fan drops the volts to just about enough to want to turn it off after a few minutes incase!
I can see the headlights fade for a moment from inside the car when I turn it on but all seems OK.
Bless.

[thesilverfox]

In simple terms
the alternator wont charge if the warning light is not working correctly, alway check that it come on, or you may change it for nothing and waste your money

The charging light goes out when the alternator is putting more in the battery than the car is taking out
it`s that simple

[thesilverfox]

In simple terms
the alternator wont charge if the warning light is not working correctly, alway check that it come on, or you may change it for nothing and waste your money

The charging light goes out when the alternator is putting more in the battery than the car is taking out
it`s that simple

[GreenV8S]

thesilverfox said:

The charging light goes out when the alternator is putting more in the battery than the car is taking out it`s that simple

The gory details are slightly more complicated than that. The alternator uses an electromagnet to generate the magnetic field needed to produce electricity. This results in a catch-22 situation where you need some magnetism to generate enough electricity to power the magnet. The small current through the no-charge warning light is fed into this coil and provides this initial mangetism. Without this current the alternator will be very reluctant to power up although depending on residual mangetism it may be possible to get it started by revving it hard. Once the alternator has powered up, the magnet will continue to be powered from the alternator output even if the electrical loads from the car exceed the alternator output (drawing curren from the battery). Once started it will only drop out again if the loads pull the alternator output below the voltage needed to power the coil, which should not happen in normal use.

[B16 RFF]

F908 TIM said:

Yep,my heater fan drops the volts to just about enough to want to turn it off after a few minutes incase! I can see the headlights fade for a moment from inside the car when I turn it on but all seems OK. Bless.

TVR are not very good at providing thick enough wiring and they don't seem to understand the subtleties of earthing very well (at least in the older cars). On my 3000M, the volts would drop to about 10 if everything was on. All the lights went out at 70 MPH on an unlit dual carrigeway when the plastic in-line fuse holder (the sort used for car radios) for the main beams melted. The car was only 5 years old at the time.

If your voltmeter reading is dropping significantly when you turn on the heater blower, it could well be just a poor/overloaded/corroded earth somewhere. Try connecting a voltmeter directly across the battery, turn on the blower and headlights and rev the engine. If the voltage across the battery shows the same or similar drop as the dashboard meter, then you probably have a problem with the alternator. If you only get a small drop (tenths of volts), then start checking the earth connections.

Paul.

[GreenV8S]

The multi-way connector between the ignition switch and the main loom is a common culprit. It takes a lot of current and is marginal when in good condition, no chance once corrosion sets in. If this fails you lose engine, lights, indicators, the lot.

[thesilverfox]

quote ( The gory details are slightly more complicated than that )
you can write pages how an alternator works, but in the end if the light stays on, it aint charging the battery, the ind ( thin wire on back of alternator )needs to become live to loss the earth from the dash bulb to make the light go off

[KentishS2]

My heater blower and the wipers both make the headlights dim when they are used and when both are switched on simultaneously the speedo flicks up and down.

Does this sound like my multi conector under the dash may be on it's way out at some point?

[GreenV8S]

KentishS2 said:

Does this sound like my multi conector under the dash may be on it's way out at some point?

Might do, but even if the connector is fine the voltage will be all over the place. Worry if you have a big drop (say less than 11 volts shown), or if the connector gets hot.

[KentishS2]

Peter, what does the connector supply, is it just about everything (ignition, lights, blower etc etc)?

I'm guessing this connector is situated above the lower steering column cowling?

I think I should check all my earthing points and this connector to make sure there is no resistance anywhere.

My voltmeter reads about 13 vots and drops to about 11 with the blower and lights on, does that sound normal?