Ignition light has decided to stay on.

[frank308d]

Hi All,
I picked up my new Mog a few weeks ago and it worked exactly as it should. Turn key, pull starter and away she goes. Oil light goes out as does (did) ignition light. No flickering light or any indication of any trouble.
Haven't fired her up for a couple of weeks and she flatly refused to go today. Took out points and rotor arm and they were kn*ck*r*d. Fitted new points and rotor arm as per instructions and she fired immediately. Will do proper service when time permits. Settled to the regular fast idle as usual on choke.
Only problem now is that the ignition light is on as though the key were turned on but the engine wasn't running. Rev the engine and the light stays just as bright. No dimming of light when revs are increased. Checked points, fine. Checked fan belt, fine.
Any ideas why this might happen suddenly? Can't see that I've pulled any leads or wires off but am open to suggestions.
Thanks in advance,
Frank.

[Pyoor_Kate]

Well...

I would suggest that you check all the connections twixt dynamo and regulator box and so on; because they may have been disturbed while you changed the points... As a quick and easy first step.

[aupickup]

sounds like the dynamo possibly

[Vernon]

Maybe the dynamo has lost its polarity. Try disconnecting both dynamo leads and use a long length of wire to connect the small dynamo terminal to the battery live terminal for 5 to 10 seconds, then re-connect the dynamo.

[frank308d]

I will check the leads that nothing has come adrift tomorrow.
Would the dynamo just give up the ghost in an instant? Or would it be a more gradual failure? If the dynamo has stayed connected all the while, is it possible to lose the polarity, again, in an instant? Not doubting the previous replies, just trying to gain a better understanding of the black art of auto electrics........
Thanks guys
Frank.

[Vernon]

Haven't fired her up for a couple of weeks

Would the dynamo just give up the ghost in an instant?

Is that an instantaneous couple of weeks?

[Kevin]

Unusual for a dynamo to just pack up with no warning, and as you have checked the fan belt it might be that the brushes in the dynamo are worn out but you normally get a bit of warning, if you cant see anything obvious that you have dusturbed have you a spare one to try in its place.
As for losing its polarity thats not something I have come across before.

[Vernon]

As for losing its polarity thats not something I have come across before.

See Technical Tips manual February 1989 page 3:1 Fitting dynamos after storage.
It happened to me when I bought a car that had been layed up for several years.

[frank308d]

I know it was in regular use until I bought it mid- December. I met the previous owner on the Saturday and we test drove it for about 1/2 hour. I left the car with him for 3 days before I was able to pick it up and it fired first time. No sign at all of any likely problems. No warning lights or low fluid levels etc. Fan belt all ok.
I have driven it a couple of times between then and now with a lay up of about 10/14 days. On the day it wouldn't start, it was a damp afternoon. Changed points and rotor arm and fired first time. The old points and rotor arm were both very worn. Ignition light now stays on bright.
Thanks for the ideas guys, I reckon I'll probably need to spend a couple of hours round it covering all the possible bases?

[Willie]

If it is a faulty Dynamo then an exchange reconditioned one is
very reasonable( the postage will be nearly as much as the price)
and they rarely fail instantly, it is usually worn brushes which are
readily available but they fail over a period of time usually,not
instantly. leaving your car idle for a fortnight would not normally
cause any problems from a dynamo. regarding checking the
connections, if you have the push on Lucar connectors on the
Control Box (on the bulkhead next to the fuses) then just slide
each connection off and then back on again, that is enough to
clean them. Ditto with the two dynamo connectors.

[frank308d]

Thanks for all the pointers.
If it appears that the connections are ok, can an auto eletrician test the dynamo and regulator?
Would it be likely to be a sudden death of another component?
Cheers,

[57traveller]

To test the dynamo insitu and assuming positive earth.
1. Make sure ALL lights and accessories are OFF, including interior light.
2. Disconnect cables from dynamo teminals marked "D" and "F" respectively.
3. Connect the two dynamo terminals together with a short piece of wire. (to produce a field current)
4. Start the engine and run at normal idle speed.
5. Connect the negative lead of a voltmeter with a scale of 0 - 20V to the dynamo "D" terminal. The positive lead to a good earth on the dynamo yoke.
6. Gradually increase the engine speed, the voltmeter should rise rapidly and without fluctuation. DO NOT allow the reading to reach 20V. DO NOT race the engine in an attempt to increase the voltage. It is sufficient to run the dynamo up to a speed of about 1000rpm.
7. a. If there is no reading - check the brushgear
b. If the reading is low - approx. 1V, the field windings may be faulty.
c. If the reading is approx. 5V, the armature winding may be faulty.

[newagetraveller]

It may be a bad connection between the relay contacts inside the voltage regulator box.

Try taking the cover off and 'touching' them.*

If they are dirty they can usually be cleaned by drawing a strip of paper between them.

*Not very descriptive here. If there is a bad contact between two of the relay contacts they can sometimes be lightly pushed together to make them work.

[Willie]

BE VERY CAREFUL if checking the regulator contacts...disconnect
the battery first because if you close the wrong contacts with the
engine off then the contacts will stay closed and the dynamo will
act like a starter motor and attempt to start the engine!!

[Cam]

Just to update you all. The problem was a stuck cut-in. It was stuck open. I had no field voltage and of course no dynamo output. After a couple of flicks, it was working and the system now seems to be charging.

I'll clean up the contact better as well as the fuel pump points as they were sticking a bit too...