Triumph Repair: 77 triumph spitfire idle battery issue, triumph spitfire, initial reading

Question
I was putting a new radio in my 77 1500 and went for a ride afterwards.  I went in to a parking lot the car went to idle then shut off and would not start back I had to push the car off and then keep the throttle up on the way back home to keep her going any ideas??  I have tried to let it run for a while with the throttle up to charge the battery and no luck.

Answer
Will,

If the battery isn't charging, it's one of two things... the battery or the alternator.  

First off, it's well worth it to spend a few $$ on a reasonable quality voltmeter.  Nothing fancy, just something that works.

Before starting the car, check the battery voltage.  It should be in the 12.4-13.6 range.  Make note of the voltage.

Next, start the car and have a friend keep the engine speed up above 2000 rpm and recheck the voltage.  It should now be up closer to 13.5 volts.

If the initial reading is low it's possible it's the battery.  If the reading with the engine running is low then it's more likely the alternator isn't doing it's job.


Cheers,

Jim