Ignition light

[BRM]

Driving home from Suffolk to Essex this afternoon, my ignition warning light came on briefly a few times. I wasn't unduly concerned as I was only about 20 miles from home.

I have an ACR type internally regulated alternator which I fitted new about six months ago, so it's not any of the troublesome relays - they're all disconnected.

What worried me was that on one occasion the light had been on for a minute or so when the ignition showed signs of missing and for a moment I thought the engine was going to die - not ideal in the rush hour on the A12. Fortunately after a few seconds the light went out and the car ran fine the rest of the way home.

I have a spare alternator so I can try that but I couldn't understand why it seemed to have an almost immediate effect on the ignition. Even if the alternator had failed surely the battery should have got me home ?

Any other ideas to explain the symptoms?

[mgcjag]

Hi Brian....could it have been the actual ignition switching off as opposed to no charge coming from the alternator........could possibly be ignition switch, or loose wire.....did tne rev counter drop......a few things to think of

[BRM]

Thanks Steve, it didn't seem that way to me. The ignition only started missing on the one occasion. The light came on briefly several other times without any apparent effect on the running of the car. I didn't notice what the rev counter was doing to be honest.

You may be right about the ignition wiring though and I'll try and check it over at the weekend. I'm thinking that maybe if something isn't perfect it may only show up when it's relying on battery power.

[Keith in Norfolk]

I sometimes have the same problem . my ignition light glows on and off for some reason , then it works fine . this may sound silly but every time I top up the oil its no problem. I was once told that the ignition light was the oil warning light ( yes daft I know ) but its seems to do the trick for me.

[mgcjag]

Hi Keith not sure what years but on early cars think all S1....the ignition warning light was wired to an oil pressure switch fitted below the carbs...so yes the ign light was really showing no pressure.....the amps were shown on the amp gauge where as S2 cars have a volt gauge.......i have had ign lamp come on intermitant before changed the brushes in the alternator and all ok

Brian how is your ign light wired from the alternator

[malcolm]

I sometimes get the ignition bulb glowing or flickering on and off on my series 2. Had this during my Pyrenees trip, and thought not good to need parts here! But then next day all is well again. Been getting this for over a year, but never fails and battery keeps up etc.

[BRM]

Steve, the alternator now only has two wires - the thick one which goes direct to the battery and a thin one which used to go to the 3AW relay. This has been bypassed so it now goes direct to the warning light.

Malcolm, I used to have similar problems, then the light was on permanently. I fitted a new 3AW relay, then it wouldn't come on at all ! But since I fitted an internally regulated alternator I've done nearly 2000 miles with no problem until yesterday.

[mgcjag]

Hi Brian so my thinking is that the only way your ign light can come on is if there is no o/p to it.....the battery could however still be charging but sugest you check out the alternator

[BRM]

Steve, yes I think it can only be an intermittent alternator fault, even though it's quite new. It would be easier to be sure if it failed completely. It's the feeling that the engine was about to die that I can't understand. I'll put my spare alternator on and check over the ignition wiring for anything obvious and take it for a run and see what happens.