Ignition Light Flickering

[TomC]

Hi all,

This morning whilst driving to work (doing about 60mph), the ignition light came on, and stayed on. I pulled out the choke once I was at the traffic lights, but the light remained on. Then as I set off again, it turned off. A minute or so later the light had a very faint flicker for a while; stayed off; came on solid; then flickered again before going off - all the while I was driving along at a steady pace.

Any ideas what this is likely to be? I only had the dynamo changed back in May so I'm hoping it's not that, and is just something relatively simple.

If it is the case that the battery isn't charging (or is only charging intermittently), how long can a full battery usually last with the headlights on? I need the car to get to and from work, and unfortunately it's stop-start traffic half the way home (about 13 miles/45 minutes of driving), so I don't want the car to die on me tonight...

Thanks,

Tom

[firedrake1942]

It indicates the charge from the dynamo to the battery so could be the dynamo, control box, loose connection at dynamo, or even ignition light or slightly loose fan belt.

[simmitc]

As above. The choke will not affect anything electrical, but will make the engine run rich. With headlights on after starting the car I suspect that 45 minutes will be pushing it without charging.

Step 1, check fan belt tension - 1/2 inch deflection at centre of longest span should be fine. If you have a multimeter then you can do some clever tests, but a basic is to rev the engine with the headlights on - do the lights get brighter with high revs and dim when the engine slows? If yes then you should be getting at least some charge. Dynamo should be under warranty. Control box is easy to change if needed; but after adjusting fan belt, if problem persists then check that all connections are clean and tight.

Remember that speedo lights, heater fan, brake lights, interior light, radio (if fitted) will all add to drain on battery so turn off everything that you do not absolutely need in order to conserve power; and use a battery charge between runs until you have the problem solved.

[Blaketon]

Assuming the fan belt it right, the voltage regulator needs to be right. There are two sets of points in there, which can be cleaned and then you adjust it with a multimeter. I can't tell you what to do, although I have done it by following a book, probably this one - https://www.amazon.co.uk/Restore-Electr ... 0850455383 (It's one of those things I don't do often enough but it's not difficult).

[Fingolfin]

Or get an MGB alternator and forget it. I wrestled with that voltage regulator for months with no luck. Went through three of them and two dynamos, trying to get the system to work - and ultimately chucked it all. No trouble with the alternator and much better charging. Though I can certainly understand wanting to make your dynamo investment work!