Neg Battery Terminal

[Jason2tpa]

While volt drop testing fuel gauge using neg battery terminal (#1) as ground it returned 11.4v. Using neg battery terminal #2 it returned 12.6v. Using neg battery terminal #3 it returned 12.6v. Batteries 1,2,3 are separate batteries.

Battery #1 is only few months old. Terminals are clean. What's happening here?

[99yam40]

A bad connection somewhere

[Jason2tpa]

A bad connection somewhere

^^^that confuses me. The power source did not change during test. The connections I was testing did not change. The wiring is brand new. The ground terminals for 2 out of 3 batteries returned 12.6v. The 3rd battery returned 11.4v.

How can this be related to connections, wire resistance, or power source when 2 out of 3 returned same volts?

By the way, this bad ground terminal is the reason I was having troubles with my fuel gauge after connecting new sender. Different thread, I'll update that one next.

[rodbolt17]

how are you doing this drop test?
most fuel senders work on a 5V setup.

[99yam40]

^^^that confuses me. The power source did not change during test. The connections I was testing did not change. The wiring is brand new. The ground terminals for 2 out of 3 batteries returned 12.6v. The 3rd battery returned 11.4v.

How can this be related to connections, wire resistance, or power source when 2 out of 3 returned same volts?

By the way, this bad ground terminal is the reason I was having troubles with my fuel gauge after connecting new sender. Different thread, I'll update that one next.

3 different batteries and using one point on negative side to get reading, means to me that they all need to be tied together with wiring somehow