9 replies to this topic

[Zacherius (again!)]

Hey all, for some reason when I turn on the ignition, the battery light doesn't come on ? ( the oil still does ).
Car starts first click, runs perfect, electrics are fine, I've checked fuses and the Earth straps ( someone said to check them ).
Any ideas ? ( not the bulb ).
Thanks
Matt.

[carbon]

Check the plug which goes into the alternator, should have 2 large wires and one small. The small wire is the one connected to the ignition warning light.

[Zacherius (again!)]

Will do. Thanks.

[Dan]

Why are you sure it's not the bulb?

[KernowCooper]

Place a wire with a male spade connector into the small terminal in the alternator plug and connect this to earth, if the light comes on, the diode pack is gone in the alternator, if not check the bulb as Dan pointed out.

 

Ensure you only touch the small terminal in the alternator plug to earth the 2 large ones will be a dead short !

Edited by KernowCooper, 13 February 2015 - 09:29 PM.

[dklawson]

Further to Kernow's advice... when you test the lamp with the jumper wire, the ignition switch has to be in the run position.

[deanymini]

I've had this problem and it was my instrument cluster. I'm sure dklawson will remember. I was always under the impression that your battery will not be getting a constant charge if this happens?

[Ethel]

It would be better called the charge light than the ignition light. It's in the wire that provides current to the alternator's windings to energise them before it starts turning and can generate the current itself. The light goes out when the alternator's voltage is equal and opposite that of the battery at the other end. 

[dklawson]

The light goes out when the alternator's voltage is equal and opposite that of the battery at the other end. 

 

Equal to the voltage at the other end yes... but not opposite.  When both sides of the warning lamp have the same positive voltage on them, there is no voltage drop across the bulb to make it light so it is "off".

[Ethel]

That's what I meant - akin to equal 'n opposite forces. I didn't put it very  well, as you say the polarity is the same.