ok can sum1 remind me how the circuit works and why the dash bulb is so important?

also, if light dont work normally that bad right... but light comes on when HFS is switched on...

WTF?

any ideas?

 

the bulb is part of the exciter curcuit , if it blows the alternator wont be told to start charging . also when the alternator stops providing enuff current the bulb will start to glow .

 

any thoughts on why the light comes on when the HFS turns on then? but dont turn on normally?

 

could it be the alternator is struggling to make enough load when u turn the HFS on. Therefore the bulb is comming on?

 

when you say hfs , do you mean heated front screen ? if so the heated screen is obviosly a controlled short curcuit , it will draw a fair bit of current . try turning on every light , heater and all other lecy bits on the car to see if the light comes on aswell (without switching the hfs on)

 

It's coming on because it can't supply enough current, or, more than likely, the voltage regulator is on it's way out.

 

what i dont get is, the bulb is OFF normally... whereas it should be ON... (engine off, ignition on) so you'd think "hmm, knackered bulb" but if the bulb comes on when the screen is turned on... so obvously not a blown bumb

wierd!

ps this aint my car...

 

has it got an alarm fitted (aftermarket) ?

 

pretty sure it has

 

Jim - it's not weird - if the alternator isnt charging, then the bulb will come on!

 

rock, but the bulbs supposed to come on when ignition on, engine not running

 

Jim, if the bulb isnt coming on at all, even when ign on, engine off, check the wires to the alternator, mostlikely one of them will have broken, one of them is only pissy and small!. Thats what happened on mine anyway.

 

right peeps this is my car! as jim says ign on engine off (red lights on dash) no batt light... but when i switch the hfs on it glows.... btw it has had 3 alternators on it today and the wires on the alternator are fine! does the wire go straight from the alternator to the dash???? is the a diode??? please help!

 

brad, it has a toad top of the range thingy on... does that matter m8? cheers lennie.

 

Right mate ..

The Alternator warning light has an ignition fed supply (in the console) to one side of the light.
The other side of the light connects back to the Alternator warning light output .. It could have been botched by connecting somewhere else .. but the Alternator terminal is where it should be connected.
When the alternator produces a charge, this will then give you 12v on each side of the warning light, yes? Now a lot of folks dont understand this bit .... The bulb will go out, cos no current is flowing.
If the Alternator fails, the regulator inside usually earths (or partially earths) this side ... so you get a light on. So earthing this wire also puts the light on.

 

Ah its as simple as that!!! I didnt know thats how they work!

 

i didnt know that either