[gmc684x4]

I am concerned over the ac voltage reading it should be zero volts

The altenator has rectifer bank to convert ac power created by the altenator to dc for usage in the truck

I am going to try this with my truck when i get it back together

31.6 ac volts the hei modual is built for 12 vdc the ripple voltage may be hard on it causing it early failure

Do you still have your other rides with the one wire alt to do the ac volt check on them to compare?