Ignition light on.

[Dek]

Dek, I think that a light was needed for either a low brake fluid or handbrake on situation so if you have no wiring to the brake fluid reservoir then it could be for the handbrake mechanism, maybe the switch needs altering slightly? Does it come on when you put the handbrake on??

No it doesn't Tony but always went off when the engine first started without any interference with the handbrake (which I don't use).

[aaronjb]

I'd also say - is it the Jag fly-off handbrake? The microswitch can be awfully trigger happy on that (at least it is on mine) and needed careful adjustment before it wasn't either permanently on or permanently off!

[Tony]

Good spot Tony as when I took a closer look it's actually a brake symbol. As there are no connections to the fluid reservoirs I assumed it was just what was to hand when fitted especially as it behaved like an ignition warning light by going out when the engine started.

Dek, I think that a light was needed for either a low brake fluid or handbrake on situation so if you have no wiring to the brake fluid reservoir then it could be for the handbrake mechanism, maybe the switch needs altering slightly? Does it come on when you put the handbrake on??

[Dek]

My mistake, My low fuel warning is from My Gauge wizard, not my toad alarm.
Copy of toad wiring attached

Thanks for that Mike it could be useful. Just wish my understanding of it was better!

[Dek]

Have you got a picture of the light Dek??

Good spot Tony as when I took a closer look it's actually a brake symbol. As there are no connections to the fluid reservoirs I assumed it was just what was to hand when fitted especially as it behaved like an ignition warning light by going out when the engine started.

[Dek]

Only one led light off the Toad to show you the status and alarming period when flashing to disarm. I don't think it will be your warning light.
 

Sorry Jon for the confusion. I've got a separate Toad alarm light and wasn't referring to that. I was wondering if somehow in the Toad box of tricks it could provide a feed to the ignition warning light from the alternator on a single terminal alternator in much the same way as an auxiliary module could in the way Aaron described.

[Mike Hamblin]

My mistake, My low fuel warning is from My Gauge wizard, not my toad alarm.
Copy of toad wiring attached

[Mike Hamblin]

Only one led light off the Toad to show you the status and alarming period when flashing to disarm. I don't think it will be your warning light.
 

You can have several lights off a toad alarm. I have a low fuel warning. And an empty fuel light. These only have one wire. You can also have a warning sound.

[Tony]

Have you got a picture of the light Dek??

[JON1D]

Only one led light off the Toad to show you the status and alarming period when flashing to disarm. I don't think it will be your warning light.
 

[Dek]

How're you getting on with it Dek? You're welcome to pop round if you want a second pair of eyes

I've hit a brick wall to be honest Aaron and even got me wondering if it isn't an ignition warning light. Only thing to my mind that would extinguish upon startup is an oil pressure light but there isn't a pressure switch just an oil feed to the gauge. When you mentioned about modules potentially being able to do this it's got me wondering if my Toad immobiliser is involved somehow? God knows what goes on in that box of tricks and of course all the wires are black to be untraceable. Might give them a ring and ask. Thanks for the offer and might take you up on it. All the best.

[aaronjb]

How're you getting on with it Dek? You're welcome to pop round if you want a second pair of eyes

[Dek]

Update. The auto electrician from NAPS returned from his holiday this week so I popped along to speak to him. He was adamant that if it was a single wire alternator there was no way it could support an ignition light. He suggested it might be some other sort of warning light, brake or oil for example. He didn't mention the possibility of a module. It hasn't got any wiring to the fluid reservoirs or even an oil pressure switch just a pressure gauge. It's a chrome Proform 100 alternator so not cheap to take a gamble and replace. Aaron your suggestion of disconnecting the bulb and relying on the voltmeter is looking a good option!

[Dek]

1-wire alternators don't (easily) support a battery light.. I think there are modules out there you can buy to mimic the standard behaviour, but as it is you might as well just disconnect your light, it's doing nothing

Long version:
A 3-wire alternator or externally regulated alternator needs a 12v feed from the battery initially to 'excite' (no blue pills here!) the field coils; before starting the engine the excite line is a path to ground from the battery - and your lamp lights up. Once the alternator starts spinning and you've excited it enough, the alternator starts putting 12v *back out* on the same wire - it's no longer a path to ground and thanks to the magic of electricity there is zero potential difference across the bulb so it goes out.

A 1-wire alternator just has one connection straight to the battery (and nowhere else), everything else is done internally.


I think the modules you can get take a switched live (from the ignition switch) and 'battery' (which will read alternator output voltage when running) and turn the bulb on when battery < 13V and off when the battery voltage is >13V.. that's a simple voltage comparator circuit in reality but easier just to buy a module from somewhere.

Thanks Aaron for that detailed explanation but fitting a module is way above my pay grade! I think I've excelled myself getting this far. I took it to NAPS who basically confirmed what I already knew ie the battery was being charged. He didn't know of one wire alternators and thought there must be a hidden wire. After going into the workshop and talking to one of his colleagues he suggested taking it off for bench testing. Hopefully they will be able to confirm an internal fault and repair it. I'll keep you posted. If they can't I did like your suggestion of disconnecting the lamp. It's superfluous as I've got a voltmeter.
Dek

[Chris]

So the ignition light is constantly on but the alternator is charging the battery . Battery voltage engine off 12.6v engine running 14.8v. Ford 302 single wire alternator. Voltage on red cable to lamp engine off 12.6v running 14.8v. Other cable to lamp (blue) goes to earth both with engine off and on. Explains why ignition light is constantly on. Question:is there anything else I can do or as I suspect take the alternator off to be tested for a low voltage return. Must admit I don't really understand how single cable alternators work. Any help appreciated.
Dek.

My mistake, didn't read that it is a single wire alt .