Battery light

[Peruzzi]

My battery light comes on, very faintly, for the first few miles of the journey, then goes out.

Does it mean anything or is it just a dodgy bulb?

[Tim2001]

Need to go and get your alternator or alternator belt checked out and your battery whilst your at it

[Peruzzi]

I had a recon alternator not long ago though. And a new battery.

Its only on really faintly, can barely see it.

[criscali]

Take the bulb out!!!!!!

[SukySaggi]

<!--QuoteBegin-criscali+--><div class='quotetop'>(criscali)</div><div class='quotemain'><!--QuoteEBegin-->Take the bulb out!!!!!!<!--QuoteEnd--></div><!--QuoteEEnd-->
:no:
Get it checked out again by the guys who fitted the recon unit.

[ross85]

<!--QuoteBegin-criscali+--><div class='quotetop'>(criscali)</div><div class='quotemain'><!--QuoteEBegin-->Take the bulb out!!!!!!<!--QuoteEnd--></div><!--QuoteEEnd-->

Someone had done that to mine, put a new bulb in a couple of weeks ago and the light comes on intermittently, no idea why though? :confused:

[Peruzzi]

I noticed today that if you have the heated rear window on, aswell as the seats, the light is faintly on.

Also, the passenger seat seems to make more of a difference than the drivers (although I dont think the drivers is working)...

[Matt]

If a lot of high load stuff is in use such as the heated seats and heated rear screen the light will start to glow a little. Basically the wiring to the back of the dash is carrying a lot of current and could do with been thicker, so the voltage at the end of the wiring drops a little. The supply to the ignition light however only ever has to illuminate the ignition light, hence the small difference causes the ignition light to glow a little.

If in doubt measure the voltage across the battery terminals with as much stuff turned on as possible, ideally you want to still read over 13 volts.

[Peruzzi]

So its not unusual for it to glow slightly when alot is in use?

[wolfy]

the light on my 8V does if have the radio, lights, or neons on.

it has never caused a problem with starting or anything like that so i wouldnt worry too much mate

J

[Matt]

<!--QuoteBegin-Peruzzi+--><div class='quotetop'>(Peruzzi)</div><div class='quotemain'><!--QuoteEBegin-->So its not unusual for it to glow slightly when alot is in use?<!--QuoteEnd--></div><!--QuoteEEnd-->

Yeah normal. if it glows with everything off, that would be unusual and could indicate a problem.

[dazjb]

Mines exactly the same. Put the lights, foglights, heated seats on and it glows quite noticeably. Been doing this for the last 2 years and never had a problem either.

[King Calibra]

find youself a calibra or vectra with a/c that has the same engine, it should be fitted with a 100 amp alternator. That might do the trick.

[Matt]

<!--QuoteBegin-King Calibra+--><div class='quotetop'>(King Calibra)</div><div class='quotemain'><!--QuoteEBegin-->find youself a calibra or vectra with a/c that has the same engine, it should be fitted with a 100 amp alternator. That might do the trick.<!--QuoteEnd--></div><!--QuoteEEnd-->

With the heated seats etc a 100 amp alternator is a good idea. The light glowing isn't because of the alternator not producing enough current though. As I have sdaid it is because of the wiring, fitting a higher output alternator will only make the light glow brighter! Cars fitted with the 100 amp alternator might have better wiring, this could help, if the light is that much of a problem.

For my money, a light that glows a little and indicates that the alternator is working well at high load is not a problem.

[MickM]

<!--quoteo--><div class='quotetop'></div><div class='quotemain'><!--quotec-->I noticed today that if you have the heated rear window on, aswell as the seats, the light is faintly on.

Also, the passenger seat seems to make more of a difference than the drivers (although I dont think the drivers is working)...<!--QuoteEnd--></div><!--QuoteEEnd-->That's exactly what mine does and has done for the last 40,000 to 50,000 miles. No problem at all when driving normally but when you start to load it all up... heated window gives a faint glow only visible at night... my seat also gives a faint glow only visible at night whereas the passenger seat lights it up enough to see it in the daytime.

If you check the wiring diagrams you will see that the way the battery light works is that one side of the light is fed from the alternator and one side from the fuse box/battery supply. When the engine is off the current flows through the bulb and lights it up as there is no output from the alternator but 12-13V from the battery. When the engine runs the alternator supplies the other side of the bulb so that both sides are around the same voltage... ie. no potential difference equals no lighting of the bulb. If you load up the alternator too much the voltage on the alternator side of the bulb drops and a greater potential difference is seen across the bulb, hence it begins to glow... That said, it could in fact be the battery that is being loaded too much and is at a lower potential than the alt..? It's all the same at the end of the day as the alternator feeds to the battery anyway. There are voltage drops along the wiring and this probably accounts for the faint glowing as the potential difference is magnified by the time it reaches the bulb in the dash...