Detecting, Fixing Electrical Shorts in 1940 6227C

[ebuliavac]

Hi Everyone,

I have no voltage from the ammeter to the alternator (converted to 12V), so there is no voltage or amps going from alternator to battery either and the car is running off the battery.  In looking for the short, I found that the lead from the ammeter to the alternator is dead.

How do I get in there to further diagnose?  In other words, do I have to remove the dash?  It seems like the only way, as I cannot fit my head in that small space.

Thanks in advance,

Ed Buliavac

[Bobby B]

Ed,
Did you check it first at the rear of the alternator to make sure it's putting out voltage? Is it a one wire alternator or one needing an "exciter"?
                                                                                                                                             Bobby

[ebuliavac]

Hi Bobby,

It's a one wire alternator.  I checked there first.  Had to get a new alternator, but it did put out voltage for a time.  It now puts out just 2-4 volts when revving the engine.  That's another issue I need to work on, but after removing the two wires to the alternator (and also checking at alternator post for battery voltage with ignition on but car not running) I got no voltage from the ammeter/battery wire.  It seems there is a short somewhere, but I can't get in there to further check it.  Nothing looks bad using a mirror and flashlight, but that's as far as I could get because of the tight physical space.

Thanks, Ed

[bcroe]

It sounds to me like an open circuit, not a short.  A wiring diagram
would be very useful, even if you need to make your own. 

I believe the ammeter is supposed to have battery voltage at all
times.  So I would probe the battery hot terminal (reference lead
to body ground) and follow battery voltage path to and through
the ammeter, continuing to the alternator.  There will probably be
a break.  Bruce Roe

[ebuliavac]

Thanks Bruce,

That sounds exactly right.  I have the wiring diagram, and want to do just what you suggested.  Just can't get in there without taking off the dash, unless there is some other way.

Ed

[pmhowe]

It is  tedious thing to do, but I have found it pays off handsomely: Take a day (or two) and clean all the electrical contacts that you can find on your car. When I have done it, in most instances, it has cured my car's electrical problems. It also taught me a lot about my car's electrical system, learning what goes where. I find that the better I know my car,  the more I trust it, and the less frequently I have a problem to address.
Good luck.
Phil

[ebuliavac]

agreed

Thanks Phil

Ed