2002 Buick Rendevous Giving 8.2 volt reading between battery gnd terminal and the chasis

Was previously getting sparks every time I connected the ground cable to battery negative terminal.
with the extra ground wire removed from chassis, I do not get that spark. Reading good 12 volts between battery ground and starter and between ground cable and positive battery terminal… ???

What is an EXTRA ground cable? What makes it EXTRA? If connecting it corrects a problem it had a purpose so reconnect it.

One goes to the engine block, and one goes to the chassis/body


There may be a poor connection within the cable itself.


You know how a typical ground cable screws into the negative terminal of the battery and then,
there is an off-shoot wire that is used to provide ground to the chassis for the headlamps. That’s the wire I removed from the chassis in an effort to find out the sparking/battery draining problem. Thanks for looking at my thread and replying Rod.

Well I’m not from Missouri Tester but obviously you need to show me before it makes any sense. It never occurred to me which wire was extra.

Without getting into a Rube Goldberg nest add a redundant ground from the engine to a good bare metal ground on the chassis and reconnect that extra wire wherever it came from just to be neat and then go about finding the cause of the discharge.

Sparking whenever connecting or disconnecting a battery cable at either end can cause a spark if there is a load on the circuit and if your battery is discharging there is apparently a load on it. If you have a test light disconnect the battery + cable and connect the test light clip onto the cable clamp and press the test light spike into the battery positive post or if it’s a side post get a bolt to hold it there. When the light is on there is a load on the circuit and if you wish to find the load one by one remove fuses and reinstall them until you find the one that shuts the light off, that’ll be the one that is carrying the load and that’s your starting point. Have fun.

Hi Rod, Thanks for all that good info on how to find what is draining a battery. Sorry I mislead you on an extra wire bit. That wire was actually a part of the negative battery cable that attaches to the frame. Chasing that difference in potential, led me to the ground connection on the engine block. What I found was that one of the four wires coming out of the harness at that grounding point was not connected. It was actually off the terminal with the rubber part of the wire touching. Once I corrected that all of those weird readings disappeared. I really gained a lot of troubleshooting knowledge, both from you and from chasing the problem. Thanks so much for your most capable assistance.


Congratulations @Edward_Ketchens. Patient persistence is a great talent.

Thanks, Good Buddy