Battery being drained

[68gmsee]

Originally Posted by Sambar56

I got a -13 in the voltmeter between the negative cable and the negative post on the battery while the truck was running. Is that good?

The best way to read the charging voltage is to put the meter neg. lead to battery neg. post and meter + lead to battery + post with cables still connected to the battery and engine running. Voltage should read app. positive 13.5 VDC or better depending on alternator. My 68 reads plus 14.5 VDC while running. It will vary some but it should be around there.

You didn't say if you disconnected the alternator completely from the battery or not but that would be the easiest way to check to see if the battery is still being drained. (forgot to add: Posts above are saying that even if it's still charging, you could have a leaking diode.)