Morris Minor Owners Club

Help!

I have managed to burn out two dynamos in quick succession.

I purchased a '56 4 door saloon which had the ignition light on all the time. I took the dynamo apart and found solder splattered around the inside of the stator. A quick with a multimeter showed that the armature windings had fused together. I fitted a new dynamo and everything seemed OK. The ignition light went out above idle speed and a voltage check of the output seemed OK. After about 100 miles of driving the light came on again. The armature of the new dynamo is burned out.

Any ideas? Would a faulty regulator or ignition coil cause this problem?

faulty regulator is most likely cause as this sounds like excessive load on the dynamo. The regulator should cut in and out when the battery is at full charge and there is no other load in the system. The regulator also prevents the dynamo acting like a motor which may also be the cause of this fault.

What acessories do you have? heated screen etc? if you do have a heated screen make sure it is off as that presents a large load to the dynamo and may be the cause of the damage.

Given that you are burning out the dymano your battery may have been seriously overcharged, take great care as that can be very dangerous.

take off the regulator cover and look for carbon marks or stuck contacts.

this link might help, it describe a regulator and how to test and adjust, otherwise it may be easier to swap for a known working one.

http://www.mgoctagoncarclub.com/articles/regulation.htm

I would also get your battery checked at a specialists, it may be faulty and demanding too much for too long from the dynamo. A quick check would be to put it on a charger which has an ammeter on it and see if the amperage decreases as normal as the battery reaches a full charge.
It will also be useful to check the Earth connection for the Control Box
which is on terminal 'E'. the wire goes in to the vertical wiring loom and emerges about 8" below the fuse box where it is earthed to the bulkhead.
It is usually hidden by the wiring loom and can be very rusty etc.

Thanks guys - very useful tips & something to keep me busy at the weekend!