MG Car Repair: alternator???????, battery hydrometer, alternator testing

Question
I have a 79 Midget.  When I drive the car at night I get a faint glow from the alternator light when I turn on the head lights, it gets brighter when I apply the brakes or the turn signals(it brightens as the signals flash).  The battery has never gone down nor has it ever failed to start. I've check grounds and checked power connections, any ideas??

thanks
Doug

Answer
Hi Doug.  By 1979 the MG factory were adding all sorts of stuff to the wiring that could cause problems, such as a diode in the brake warning circuit and another for the service interval warning lamp.  However, this fault seems to be affected by almost any load, such as the turn signals.  I suspect that either the battery is reaching the end of its life, or the alternator is starting to fail.  I have the equipment to test both of these items (a battery hydrometer and an alternator testing device made by a US company called Blue Point).  If you do not have this equipment, then I suggest you pay a visit to a battery supplier who can do the test on the spot.  

The alternator uses the battery as a reference voltage, therefore a faulty battery can blow a good alternator, so do not ignore this problem.