Battery Light?

ste_bla

ste_bla

ste_bla

Soldato
Joined
9 Aug 2004
Posts
7,795
Location
Milton Keynes
Got an omega and have tried on some owners site, however they dont know or completely guessing..

So changed the plugs on the omega, the 4th one for some reason had 2 washers on looks like someone left it in from prev change (only just got given car). Put leads back on and started the car.

I think it sounds the same i think there might be a slight wine however not sure if just noticed now as something else is wrong. Now the battery light comes on bright (like when the alt is dead) and then if you rev the engine the bulb gets VERY bright and blows. Now the alternator isn't charging the battery however been told this is as when bulb goes it means the circuit breaks and stops it as a safety feature (sounded a little odd but that what a garage told me).

Some people think one of the following;
1) Theres a fault with the plug leads
2) The alternator is overcharging
3) I ****ed an earth wire up

Which one is most likely as dont want to spend out £60+ to then find out its not the alternator.

Cheers for any advice steve
 
12.47 but thats without the bulb (and therefore possibly the recharging bit working) havent any more spare bulbs to test tonight.
 
13.7 is a standard alternator output. You need a voltage differential for the battery to charge.

If there isnt enough differentially the battery light will illuminate indicating a stuffed alternator.
 
Anim said:
I thought they were meant to charge at half a volt so 12.5 seems about right?
Click to expand...

Nope! I'd expect a fully charged "12V" battery to hold around 12.7V of charge alone without the engine running (and therefore the alternator charging). 12.47V is ridiculously low for a running engine. I'd personally expect anything upwards of 13.5V if everything was working as it should.

ste_bla said:
Screwed up double checked its 11.47 not 12 so thats even worse
Click to expand...

Are you sure you messed up? You COULD have an alternator that isn't charging at all (and is therefore flattening your battery at a ridiculous rate)?
 
Well the bulb has blown which the garage said would stop it charging or doing anything will go buy a £1 bulb tomorrow and test again
 
The light in the dashboard behind the "not charging" indicator blowing absolutely will not stop the thing from charging.

If the it really has blown and the car has a rectifier, I'd look at that. Otherwise, the alternator is probably dead.

Make sure it's turning, rather than the belt slipping on its pulley making that whining noise.
 
I drove a car once without the instrument cluster in...

The battery went flat. Seems the light is part of the actual demand circuit.
 
Jonnycoupe, depends how it was designed. Too late to go out and see if this is covered in the Haynes manual for other cars in the wiring diagrams tbh.
 
BigglesPiP said:
The light in the dashboard behind the "not charging" indicator blowing absolutely will not stop the thing from charging.

If the it really has blown and the car has a rectifier, I'd look at that. Otherwise, the alternator is probably dead.

Make sure it's turning, rather than the belt slipping on its pulley making that whining noise.
Click to expand...

The alternator has a rectifier inside it i think after taking it apart and looking at ebay pictures
 
As said, on a lot of cars, not having the battery indicator bulb connected will actually cause the alternator to not charge the battery
 
Wow, that's a new one to me. It means somewhere out there this happened in a meeting:
"If this bulb blows the car will break down."
"OK, that's a go for production."

Is it a component used to test the alternator is functioning correctly? Why not use a resistor which isn't all the way through the loom to the dash?
 
BigglesPiP said:
Wow, that's a new one to me. It means somewhere out there this happened in a meeting:
"If this bulb blows the car will break down."
"OK, that's a go for production."

Is it a component used to test the alternator is functioning correctly? Why not use a resistor which isn't all the way through the loom to the dash?
Click to expand...

The charge lamp supplies the excitation current to the field coil within the alternator. It requires this to start charging, and once charging the alternator can supply it's own field current. An alternator MAY have enough residual magnetism to start charging without the lamp, but you can't count on this.

Some alternators have a separate connection to the battery and the charge lamp is simply for diagnostic purposes.
 
Odd way to drive the field coils, I much prefer the direct method, but this does mean the alternator goes loopy if you unplug the battery with the engine running.
 
You must log in or register to reply here.
Back
Top Bottom