Moss Motors, Ltd

The alternator lamp is dim all the time on my 73 MG Midget.  I've checked the grounds, replaced the brushes and checke dteh tension on the belt. 

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David L Brown

Spridget 60/74,

That lamp shows a difference in potential (voltage) between the output of the generator and the battery. If the generator is spinning too slow, or not at all, there will be a difference and the light will come on.

Are you having any other electrical problems with the car?

Will the light be brighter if you turn all the electrical power on, (fan, headlights, radio etcetera)?

Did this problem just start, or has it been like this a while? If so, how long?

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On their death bed, nobody ever said, "Gee I wish I'd spent more time at work!"

'68 Sprite 1275
'76 Midget 1500

I am having no other electrical problems with the car.

The light does get slightly brighter when I turn on the halogen headlamps

I've had the car about 15 years but just started driving it about a year ago.  The car has been completely rewired with new wiring.  I only noticed the light when I started dirving it regularly. 

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David L Brown

As fate would have it, I just developed the same problem with my '76 Midget. Here's what I'm going to do...

1. Check the battery contacts.

2. Check the chassis ground strap.

3. Put a voltmeter between the generator and battery...If all is well, it should read zero volts. The lower voltage side (watch polarity) indicates the side with the problem. In other words, if the battery has less of a voltage than the generator, it's time for a new battery, if the generator has a lower voltage, that's where the problem is. It may be a loose belt, gummed up commutator or poor connections, but at least I'll have isolated the problem.

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On their death bed, nobody ever said, "Gee I wish I'd spent more time at work!"

'68 Sprite 1275
'76 Midget 1500

Well, I hope this helps...

I did a bit of troubleshooting tonight and determined that the problem must be worn brushes (probably).

A check of the book then told me that the brushes have about a 60,000 mile (100,000 km) lifespan. I wish I'd read that first!

In any case, I'll be removing the alternator even though my Midget has only 48,000 miles, at least I'll be eliminating that as a possibility. ...or perhaps I'll put an oscilloscope on it first, just to confirm...I'll let you know...

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On their death bed, nobody ever said, "Gee I wish I'd spent more time at work!"

'68 Sprite 1275
'76 Midget 1500

Hopefully, this will be the last update here...

The alternator does not have to be removed to change the brushes. Pull the wiring connector, remove the black plastic cover (2 screws, 1/4" drive), to expose the brush housing - white plastic. The brush sets are held in there with 3/16" screws.

I inspected the brushes and found them depleted, I have new brushes in the mail. - - - The excitement continues to build!

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On their death bed, nobody ever said, "Gee I wish I'd spent more time at work!"

'68 Sprite 1275
'76 Midget 1500

Hm, defiitely a timely reminder from Davey. One,  I !,   tends to think once one has an alternator installed thats it, no more charging problems cf running with a dynamo where regular inspection/maintenace was recommended. In fact many moons ago, in my dim[sic] and distant youth I  had to make up a special dynamo tool. A lollipop-stick with a piece of absorbant cloth bound on it which got used frequently on any journey over about 5 miles to wipe the oil off the dynamo comutator. Max output from the dynamo was about 8 amps. Theres a virtual pint for everybody who can guess the make/model car involved!!

Thanks for the reminder Davey, oh, Im intrigued as to what you were intending to do with the oscilloscope??                 Cheers    - - - - - -       steve

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To a man equipped with only a hammer, most problems look like nails

Believe it or not Steve, my o-scope gets more use than my multimeter! Asides from being able to measure DC voltage, it will also tell you if you have a shorted rectifier diode (or two)! You can actually see the DC unlike what the meter will show. It's just a matter of preference I suppose.

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On their death bed, nobody ever said, "Gee I wish I'd spent more time at work!"

'68 Sprite 1275
'76 Midget 1500