Ignition Light won't go out

Simeon · Post by **Simeon** » Tue Apr 26, 2011 8:31 pm

I have started the dash wiring on my westfield and connected the ignition light. When the ignition is switched on the light comes on wahay! however with the engine running the light stays on.

I have linked to a photo of the alternator so I can explain my connections. The alternator is new and I checked the charging with a charging checking gadget that shows it is charging the battery.

On the large post in the black plastic moulding at the back of the alternator the two large wires are connected, one which goes to the starter motor and then on to the battery and the other i think provides power for the loom.

The brown and yellow small lead goes on to the small post. The only marked connection is the other large post which is marked W but I don't believe that is relevant.

The male spade connection? every time I touch it with anything it sparks at me!!!!

Any ideas

DEVONMAN · Post by **DEVONMAN** » Tue Apr 26, 2011 10:07 pm

One side of the ignition light should be connected to 12v ign live and the other side of the light should be connected to the small terminal on the alternator,
The spade terminal is for a suppressor.
Regards Denis

ChrisJC · Post by **ChrisJC** » Wed Apr 27, 2011 6:51 am

The W terminal is for a rev counter.

Chris.

Simeon · Post by **Simeon** » Wed Apr 27, 2011 7:23 am

Thats the way I have it. One side of the ignition light goes to an ignition live and the other goes to the brow/yellow lead on the small post. Could the fact I am using an LED ignition light be the problem?

DEVONMAN · Post by **DEVONMAN** » Wed Apr 27, 2011 8:01 am

Simeon wrote:Thats the way I have it. One side of the ignition light goes to an ignition live and the other goes to the brow/yellow lead on the small post. Could the fact I am using an LED ignition light be the problem?

Yes, It's not normal to use an LED. It may work if you reverse the LED but really you need a low wattage bulb.
When you fit the bulb the engine may not stop when you switch off as the alternator will be feeding the ign circuit through the bulb. If this happens you need a lower wattage bulb or you need to fit a diode in the feed to the bulb.

Regards Denis

Simeon · Post by **Simeon** » Wed Apr 27, 2011 8:05 am

I tried reversing the polarity on the LED which made it not work at all. I will try and use a low wattage bulb as you say and wire it in series to the LED.

DEVONMAN · Post by **DEVONMAN** » Wed Apr 27, 2011 8:18 am

Simeon wrote:I tried reversing the polarity on the LED which made it not work at all. I will try and use a low wattage bulb as you say and wire it in series to the LED.

It won't work in series.
But try in parallel.

As a test, disconnect the B/y wire then connect the bulb to small terminal under the bonnet and put the other side of the bulb to the battery +ve.
The bulb should light and go out when you start.

DaveEFI · Post by **DaveEFI** » Wed Apr 27, 2011 9:09 am

I posted a reply to this which seems to have disappeared. ;-(

LEDs are polarity sensitive.

A common warning light is 2 watts which will take about 17 mA, so not very different from an LED.

I'd try a normal 2 watt bulb first. You can have an alternator fault where the light stays on, but still charges. Or the other way round.

If it then works normally, increase the current in the circuit by wiring a resistor across it. I'd go for a 100 ohm 3 watt type. That could be sited at the alternator or warning light end.

ChrisJC · Post by **ChrisJC** » Wed Apr 27, 2011 10:03 am

You have to use a bulb as the current through the bulb is used to bootstrap the alternator when it starts spinning. Without it, it may not ever generate (it might do however with the residual magnetism.

On some vehicle dashboards, a resistor is fitted in parallel with the charge bulb, so the alternator will still work even if the bulb goes.

You should stick a suitable resistor in parallel with your LED.

Chris.

Simeon · Post by **Simeon** » Wed May 11, 2011 9:32 pm

Just to let you know chaps

Fitting a warning light in parallel fixed it.

Thanks for your help

Now off to the cooling area for my next post

SuperV8 · Post by **SuperV8** » Wed May 11, 2011 11:05 pm

Just to add i'm using an LED and seems to work ok, doesn't go out/start charging until I raise the revs a little so the alternator self excites! but that doesn't really bother me.

When the dash is out next I may put an resister in as sugested.

Tom.

DaveEFI · Post by **DaveEFI** » Thu May 12, 2011 8:01 am

SuperV8 wrote:Just to add i'm using an LED and seems to work ok, doesn't go out/start charging until I raise the revs a little so the alternator self excites! but that doesn't really bother me.

When the dash is out next I may put an resister in as sugested.

Tom.

Interesting. I'm now running a later type alternator (100 amp) but the previous one did just that. It was a Quinton-Hazel replacement and although a direct swap for the original Lucas looked slightly different. And was listed for a Jag XJ6 - the Q-H cat. didn't give a 75 amp one as fitted to AC EFI SD1s. So perhaps the XJ6 uses a different warning light.