commentator

BIL has a Trailblazer with a 4.2, '03 (?), ~95KM.

Voltage gauge 'pulses', swings up and down, sometimes between 13.5 - 14.5,
other times between 9 - 15. He removed battery ground with the engine
running, no change to behavior. No codes.

Voltage regulator?

TIA

whitelightning

Sounds like the voltage regualter whicvh is part of the alternator. also
tell
him to be ready to place the ecm since he tried a test metyhod that went
out 30 years ago. Disconnecting the battery while a vehicle is running and
then
reconnecting it causes massive voltage spikes which cook computers. Hell
jhooking a set of jumper cables up without shuting the donar vehicle off
first can
cook computers. same with disconnecting them.

Whitelightning

commentator

I was thinking the same thing on removing the cable, but he didn't ask, he
just told me about it after the fact.

Thanks.

whitelightning

Sounds like the voltage regualter whicvh is part of the alternator. also
tell
him to be ready to place the ecm since he tried a test metyhod that went
out 30 years ago. Disconnecting the battery while a vehicle is running and
then
reconnecting it causes massive voltage spikes which cook computers. Hell
jhooking a set of jumper cables up without shuting the donar vehicle off
first can
cook computers. same with disconnecting them.

Whitelightning

commentator

I was thinking the same thing on removing the cable, but he didn't ask, he
just told me about it after the fact.

Thanks.