Technical Current draw issue

[trulyh8ful01]

1973 fiat 850 sport spider i inherited that had sat for 20+ years motor was stuck and disassembly had been stated on the entire car. Then it sat untouched for many, many years. I got it running again, just finished up new brakes and lines. My main issue right now is before I turn the key I have 11.6v on the battery and as soon as I turn the key it drops to 9v even when running it won’t charge up to 10 but as soon as I shut it down I still have 11+ volts. Also need many many parts that are missing from the body

 

[ZaphodB]

First question would be how healthy is that battery ??

Then if it is a known good battery I'd retest with fuses pulled (and then refitted) one by one

 

[trulyh8ful01]

Battery is a interstate less than a year old, I will try the fuse idea though

 

[ZaphodB]

and this is still a dynamo, not an alternator correct ?

Battery is a interstate less than a year old,

Used recently successfully elsewhere?

 

[trulyh8ful01]

It’s an alternator. How does a person test the external voltage regulator

 

[ZaphodB]

It’s an alternator. How does a person test the external voltage regulator

In the absence of being able to monitor the actual current flow **, to be able to charge the battery any system must be able to overcome nominal battery terminal voltage.

So with the engine even at idle , a working alternator and regulator must be shown to bring the battery terminal voltage up by some degree.

Check and report battery voltage with engine off.
Check and report battery voltage with engine idling
Check and report battery voltage with engine at slightly elevated revs, say 2K

Let us know what you read


(** you could read current flow by adding a high wattage ultra low value resistor in series with the battery and measuring the voltage across the resistor, but a voltage reading as above will give enough general info as to what's occurring)