Is both grounding wires from the battery necessary?

[Libertying]

I'm wondering why there is the second ground wire going to the chassis?

[iisshhyy]

Unfortunately I can't provide you with any sort of answer, but I'I'm curious all the same. Why are you asking this question? (not meant in a smart ass way or anything)

[Libertying]

My battery died and I decided to go for a more univeral battery. So I just got wider terminals, and in changing the negative ground wire I found the second ground wire! So im wondering if i can just have the grounding wire on the engine and not the second smaller one, or if I can solder the smaller wire onto my new ground wire? (If that makes sense!)

[arrow224]

The battery should have 3 main cables attached to it.

1x Positive for all electrical devices within the car. May be split (to go to different devices) into various cables of varying thickness depending on devices.

1x Negative for grounding of engine block.

1x Negative for grounding of chassis.

All the electrical devices use the chassis as ground. EG, lights. Positive from battery to light, negative from light to chassis. This does not complete the circuit to the battery. So the chassis acts as a conductor, and then a cable from it to the battery completes the circuit.

This is what is known in the car audio circles as the "Big 3". When they mention the Big 3 Upgrade (typically to reduce/eliminate dimming of lights on big bass notes), they upgrade (to a thicker cable) the 3 cables - positive to alternator, negative from battery to chassis, negative from battery to engine.

Edit: for more info on the Big 3, http://www.the12volt.com/installbay/for ... 73496~PN~1

[AlpineRaven]

Yes I've done that before, I noticed the negative wire was slightly warm one time with full blast heater, lights on full beam etc, I installed thicker gauge wire from battery to chassis, from battery to engine was okay, I will do that for my Gen 4 Liberty soon.
Cheers
AP

[al_cam]

Ground to Engine block is needed for things like sensors and injectors. Sensors need to accurately measure voltages or currents, so shouldn't rely on grounding through metallic parts like pipes, shafts etc. Also takes electrical noise & spikes back to battery which acts like a big capacitor to smooth them out.

Probably also a bl***y great braid from block to chassis somewhere to take high starter motor current.

Don't be tempted to leave off any ground wires the Factory put in. May result in something like odd noise on the radio, or some sensor sending odd signals.

AL.

[sheppo9]

Don't be tempted to leave off any ground wires the Factory put in. May result in something like odd noise on the radio, or some sensor sending odd signals.

Add possible Electrolysis to that list too.
http://www.ve-labs.net/electrolysis-101

[Ric]

...
Probably also a bl***y great braid from block to chassis somewhere to take high starter motor current.
...

That's going through the thick cable linking battery negative to the engine block.
The two highest ground currents in the car flow through it:
[1] Starter motor
[2] Alternator
Neither of those go through the chassis.

[kiks]

Dont remove earths.

[Robbks]

Dont remove earths.

Add more instead.
and make sure that they're in good condition with good clean contact areas