Temporary ignition warning light problem

[myoldjalopy]

Hello,
I parked my car and switched off the ignition, took the key out of the barrel, and noticed ignition warning light was on! It then started up OK and the light went out. But when I switched the ignition off, the light came on again. Then after a very short drive, all was back to normal. I'm guessing the control box cut out contact had stuck closed for some reason, and then got unstuck from egine vibration or something. Any thoughts? Anything I can do to make sure it doesn't happen again?
Thanks,
Pete

[DAVIDMCCULLOUGH]

I would clean them, put a bit of paper or really light emery through the contacts. Keep an eye out for it again.

[mike.perry]

Take the cover off the control box and check that the cut out is not staying closed when you switch off the ignition

[myoldjalopy]

Thank you both, I will check it out as advised.

[myoldjalopy]

Hi guys,
I cleaned them up with paper a couple of months ago and all was fine - until today
I noticed the ignition light took more than usual revving for it to go out and then, when I put the car to bed, so to speak, I noticed the light was on after turning the ignition off! When I turned the ignition on again (didn't start the engine), the light went out! So I started her up again, revved the engine and got things back to normal. Ignition off, light out.
But there is clearly something wrong
Maybe I should resort to a bit of emery now? Annoying as this control box is only a few months old, and the last one barely lasted a year. I need to watch this - what's the worst that could happen if it recurs and I don't notice it for some reason?

[DAVIDMCCULLOUGH]

Worst case is that the dynamo trys to spin as the contacts are closed and this heats up and melts wires.

I saw this happen on a car that had just been restored and it was the first run out, smoke was noticed coming from under the bonnet and the insulation had melted off all the wiring down to the dynamo. The battery was then disconnected very quickly

[myoldjalopy]

Oh dear..............has anyone else suffered a dodgy new control box? Its taken me 15 years to gradually restore my car and I don't want it burnt out now

[bmcecosse]

Where did the 'new' control box come from? I doubt there are any made in the UK nowadays. Or did you get a 'new old stock' box? And yes - always check very carefully to make sure that light goes out.

[mike.perry]

Fit an ammeter, if the light stays on and the gauge reads max discharge disconnect the battery quickly

[myoldjalopy]

Roy, it came from ESM................yes, some parts just aren't as good as they should be. These units SHOULD work for decades - like they did in the good old days..........I will have another look at it.

[myoldjalopy]

Pah! I cleaned up the cut out points with fine glasspaper and all worked OK for a couple of days - except it took more than usual revving to get the light to go out, but when it did go out, everything behaved as normal, light stayed out even on tickover. But today the red light won't go out at all, even on maximum revs At least it does go out with ignition off.........
Looks like ANOTHER control box required!

[bmcecosse]

Check all the connections first.

[myoldjalopy]

Moral of this story is don't ASSUME anything.............

I checked connections....all OK. So I fitted a new control box.......same problem! So........where I went wrong was, because I had a charging problem about four months ago and had checked the dynamo (which was fine) I ASSUMED the dynamo was still good. Mistake! And because the problem then had been the control box, I ASSUMED it was the control box again (especially with cut-out points not separating on turning off the ignition). Mistake!

In a flash of inspiration, I tested the dynamo.....at speeds where it should have been giving out around 14v it was only giving out around 2 or 3v. The good news is a new dynamo and all is working ticketty-boo again AND I have a spare control box

BUT two questions:
1. Why would a dynamo that was only giving a good charge at high revs cause the cut-out to stay closed with ignition off?
2. Given the brushes look fine, can the old dynamo be easily fixed to make a spare?

[ianmack]

I'm not sure about your first question but it would be worth having a look in your dynamo. If the windings or commutator are damaged it has probably had it but a good clean may help, especially cleaning the commutator. If the brushes are OK have a look at the springs holding them in place. Mine stopped charging recently and the springs were rusty and the end had broken off one of them. New springs fixed it.

[bmcecosse]

The answer from me is - I don't see how the dynamo could cause these problems - but the 'stuck in' contact points may have damaged the dynamo. Hence you now have a 'new' control box and a new dynamo - and of course the system works!

[myoldjalopy]

Hmmmm....that is an interesting thought. There is one conundrum though.........Disregarding the old control box for the moment, the contacts on the NEW control box remained closed when the ignition was turned off, but now separate EVERY TIME on turning off the ignition since the new dynamo was fitted. So we had a control box that didn't function properly until a new dynamo was fitted. Strange, huh?
I'm pretty sure that if I put the OLD control box in now with the new dynamo, everything would work fine. But I can't be bothered as I've spent enough time faffing around under the bonnet for now and am just enjoying driving again.

[bmcecosse]

Well indeed that is a mystery -\i thought you had fitted yet another 'new' control box - and then a dynamo..

[myoldjalopy]

It is strange. But then, electricity is strange stuff. Perhaps some electrical wizard will come along to answer.

In the meantime, back to the old dynamo:
Given the brushes (and springs) are good, I'm guessing one or other of the windings has failed in some way. BUT (vain hope maybe) if I clean the commutator and armature, can it be easily tested on the bench with a 12v battery, some electrical wire and a voltmeter?

[ianmack]

If you clean it and there is no sign of damage reassemble it. It can be bench tested by joining the two terminals together and connecting them to a battery and connecting the battery's other terminal to Earth on the Dynamo body. It will spin if all is well. Do this test only briefly as it is said not to be very good for the dynamo.

[bmcecosse]

It just runs the dynamo as a motor - won't do it any harm.