Help please! Dynamo charging light stays even when ign. off

Post by **Dominic** » Sun Sep 17, 2006 4:29 pm

Hi folks

I've just replaced bearings and brushes in the dynamo, and when I started up, the red light came on, then became brighter, before dimming, but remaining on. I switched off the engine, removed the key, and to my consternation, noticed that the charging light was still on! I quickly disconnected the battery. (I have one of those screw contacts so that it can be isolated without having to remove a cable from the terminal) When I unscrewed the isolator, as the circuit was broken, it sparked. This has never happened before.
My initial reaction was that the dynamo was at fault, but I replaced it with another dynamo, same problem.
I also tried the low tension cables to the coil in both positions, it made no difference. Am I right in assuming that the black and white wire from the distributor goes to the +ve contact on the coil? The car is +ve earth.
Any ideas would be very gratefully received!
Cheers chaps.

Post by **8009STEVE** » Sun Sep 17, 2006 4:50 pm

Check the voltage regulator. if the points are fused closed it will keep the red light on

Post by **Dominic** » Sun Sep 17, 2006 5:07 pm

Just checked, the right hand (looking from the front) points have fused, and the tip has snapped off, looks as if burnt through. This is the one that has the heavy duty brown & brown/blue wires connected to a common conector. Any ideas why this might have happened? More importantly, what needs to be done to avoid blowing the next one!
Thanks, Dom

Post by **minor_hickup** » Wed Sep 27, 2006 11:40 am

I'm also having this problem. Last night I fitted an alternator to the mog and have wired the electrics in according to Jon's dubious guide to fitting a 1275:

dunketh wrote:Wiring:
If you've fitted the Morris dynamo to the MG block the wiring will be all the same. Lucky you, although don't cry to me when your wipers slow down and your lights are too dim.

If you have done the decent thing and chucked it in the bin in favour of an Alternator....

Fit the BIG cable from the dynamo to either of the two BIG terminals on the alternator.
Fit the SMALL dynamo cable to the SMALL tab on the alternator.
Now we need to examine the voltage regulator box.
On Terminal E there should be one or two thin black cables. Disconnect this/these and earth it/them to the body.
There should be a thin brown and green wire on Terminal F, disconnect this and connect it to the THIN brown and yellow cable (or plain yellow in some cases) from Terminal D.
Connect the remaining THICK wires from Terminals A, A1 and D all together.

There should now be no wires attached to the voltage regulator. This box can now be removed.
All the other wires in the engine bay can be connected as they were on the Minor engine before.

I've checked and double checked that my wiring is as per the guide and have removed the control box. However when my ignition is off the red light is on and when it is on the red light goes off. Have I dont something wrong here?

Post by **Kevin** » Wed Sep 27, 2006 2:31 pm

according to Jon's dubious guide to fitting a 1275:

Oh I remember that posting
It recommended fitting a minor flywheel with 2 bolts intead of the correct number of 6 and to put a spacer behind the fan to make it even nearer the rad and he quoted that the engine was from an MG when it turned out to be a Marina one.
I know this is going to sound silly but missing from the so called guide is the fact that an alternator is Negative Earth and the battery will need turning round and care will be needed to make sure the battery clamp still has enough clearance and swap the coil wires around, if you are unsure look under technical tips changing to negative earth.

Post by **minor_hickup** » Wed Sep 27, 2006 4:17 pm

I'm already negative earth, I changed that when I fitted a radio last year. I followed the guide to a T and have double and treble checked I did it right but still the ignition light comes on when the ignition is switched off! I know Bigginger had success with this method which is apparently as outlined in the Owen Burton Morris Modification manual.

For now I may just remove the ignition light bulb. It seems to be charging as there is no dimming of the lights which are very bright and the voltage gauge reads just over 12 volts constantly.

Post by **alex_holden** » Wed Sep 27, 2006 4:53 pm

12V when the engine is running sounds too low. Charging voltage with an alternator should be about 14V.

Post by **minor_hickup** » Mon Oct 02, 2006 7:23 pm

You're right, the earth lead was not tightened. Which I rectified and it now sits at between just under 14 or just under 15 fully loaded (all electrics i can think of on) and nothing respectively. Which seems good.

The brown and yellow cable obviously powers the ignition light. I have cut the connection to the brown and green wire from terminal F which stopped the ignition light coming on. But i still don't know why it was coming on in the first place as I have followed the guide to the letter!

Post by **nebogipfel** » Mon Oct 02, 2006 7:45 pm

You did say the guide is dubious (yes I have read it)

Auto electrics is not my thing but it sounds as if you have connected the warning light to a constant 12v source?

If memory serves (it probably doesn't) I think the WL wire on the ACR alternators is fed from to the small terminal on the alternator?

I'm sure someone can confirm

Post by **blueangelical** » Mon Oct 02, 2006 8:27 pm

I had the same problem with the light, I took the car on a really long drive, and it went out and haven't had the peoblem again. Try yaking it for a long drive to really boost the battery.

Post by **minor_hickup** » Sun Oct 08, 2006 5:41 pm

Nebogipfel, I you're right. The small tab on the alternator is what has been connected to the warning light. So when I have it connected and the problem (light coming on when ignition is off) is possibly an alternator fault it would seem. I may try and get another known good alternator and try it.

Post by **minor_hickup** » Sun Oct 08, 2006 9:41 pm

Its sorted now. Turned out to be a dodgy connection on the alternator that needed cleaning up.