Ignition light

[Gmg31]

Am I wrong but my S2 doesn’t appear to have an ignition/charge light? There’s nothing in the wiring diagram. Does anyone know how to retro fit one?

[EuropaTC]

You should have a set of three lights between the rev counter/speedo, Red, Green & Blue, Mine is a TC but AFAIK the basic set-up is the same as yours. The second image is an alternator charging circuit which shows where the warning light should be.

It's pretty crowded behind the dash, if your light isn't coming on then I'd check for connections before anything else. There's also something in my mind about the bulb rating being important, get the wrong rating and it doesn't extinguish properly as charge builds up. If that's the problem I'll dig through my notes, I seen to recall I had that problem at one point.

Brian

[Stuleslie]

Brian, that’s an interesting point regarding the bulb rating. I thought I would be clever and change all my lamps to leds only to find out that the charge light would not go out. I then changed back to a new tungsten lamp but now I need to rev over 3000rpm for it to go out. I must try to find the old lamp and see if it will go out at lower revs.
Stuart

[jbcollier]

The lamp provides the current for initial excitation of the rotor’s field coil.  If the bulb has too low a wattage rating,  not enough current will flow through the circuit.  This usually leads to the engine having to be revved quite high before the alt’s internal regulator kicks in.  Once the internal regulator kicks in, it supplies system voltage  to the feed from the bulb, turning the ignition light off.

If the light continues to glow dimly, this means that a field supply diode has failed and the regulator is unable to supply system voltage either to shut off the light or to fully excite the field, leading to reduced output.

[EuropaTC]

Brian, that’s an interesting point regarding the bulb rating. I thought I would be clever and change all my lamps to leds only to find out that the charge light would not go out. I then changed back to a new tungsten lamp but now I need to rev over 3000rpm for it to go out. I must try to find the old lamp and see if it will go out at lower revs.
Stuart

I'm hesitant on this post because my memory is very hazy, but I think my experience was similar to what you've seen with your LEDs. I think it was when I decided to clean all the instruments (I do remember doing that  ) and as I had everything apart I decided to fit new bulbs throughout. Shortly after I noticed the red light only went out when I revved the engine but I just put it down to "Lotus" and not my tinkering.

Later I found some detail about how the wattage of instrument bulbs was lower than that of the warning light bulb. I can't recall if it should have been 2w but was now, thanks to my "improvements", only 1.2w or if it should have been 3w but was now 2w. The article went on to show how you could fit a resistor or another bulb in parallel, but I just bought a higher wattage bulb and the warning light goes off as soon as the engine fires.  Sometimes my car doesn't want to be "improved"......

 
 

[Gmg31]

Thanks for the above advice. I’ve sorted much of this but just need to decide which of the terminals on my alternator needs to be connected to the earth on the ign light.  Mine is different to the one above. There are clearly only a couple of candidates and I suspect it’s the bottom left earth terminal but would rather not guess if anyone knows for certain please.

[Stuleslie]

Be careful, you are not looking for an ‘earth’ for your ignition light. One end shares +ve with the  tacho then to the fuse. The other end should go to the regulator terminal on the alternator. The light indicates the alternator is working by comparing voltage from the battery (12V) and the controlled output of the alternator. So when the ignition switch is on but engine not running the voltage at the altenator is below 12V so the light is on. When the engine is started the light may still be on until the revs are high enough to switch the regulator on to output a charge (13-14V).
I have not seen the alternator in your picture before but I suspect the regulator terminal is at the top coming out of the insulated plate. I must stress that you try to find the exact wiring diagram for your alternator before connecting the lamp.

[jbcollier]

That alternator requires an external regulator.

[Gmg31]

Spoke to Richard at Banks today and he said, the S2 with original Renault engine and alternator does not have an ignition light and one cannot retrofit because it will blow the diode in the alternator.