Does new one wire alternator also require ground wire?

Ready to install a new Ebay alternator in place of the old Paris-Rhone on my AQ131A and my understanding is that all it takes is a one wire connection from the alternator to the large lug on the starter solenoid.

However, in researching some past posts, some talk about also having a ground wire attached.

Does anybody know if that ground wire is necessary? Thanks.

All alternators should use an additional Chassis to Engine Negative cable.
Otherwise, you'd rely on the mechanical mounting only.


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Ayuh,..... Agreed,.... Even though it'll probably ground through the mountin' points, you can never ever have to many grounds,....

Clean shiny metal, tightened, 'n greased,....

Should have a seperate ground wire. Never a good idea to rely on a load bearing fastener to also pass current.

Thanks folks. I will install a ground wire from the new alternator to the battery negative post. The engine is presently mounted on a pallet preparatory to being started up for the first time since I began work on it a couple of years ago, so wish me luck.

film842 said:

Thanks folks. I will install a ground wire from the new alternator to the battery negative post. The engine is presently mounted on a pallet preparatory to being started up for the first time since I began work on it a couple of years ago, so wish me luck.

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First off, ground refers to "earth ground" that is used and required for land based Alternating Current applications!
12 vdc systems incorporate a Positive and Negative only.
I know... I know... you'll see the word "ground' used quite often in 12 vdc discussions and literature......., but it is not technically correct!


Be that as it may...... your Marine Engine Block is your "system negative common"!
Your battery bank Negs (as in each bank independantly) are to connect to your "system negative common"!
Your starter motor, for example, offers the greatest load. The shortest path for the starter motor Neg, is in it's mounting to the engine block.

All other negs can also connect to the "system negative common".
Or..... for the lighter loads, these can connect to a remotely located Neg terminal block that is still a system negative... but not "system neg common".

The engine alternator requires a chassis cable to sys neg common.
This cable runs from the alternator chassis to the engine block.
If not, then we rely on the integrity of the mounting hardware... of which can be sufficient... but the factory prefers a chassis neg.
You'll typically find a lug for this short cable right on the chassis.
The engine block should offer a near by small threaded hole for the cable's terminal bolt.


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If you went with a lot higher amp alternator make sure the wires are big enough to handle the new load.

CASTLE_CAPE said:

If you went with a lot higher amp alternator make sure the wires are big enough to handle the new load.

Click to expand...

Great point!
I have occasionally seen where an owner had increased his alternator output, only to over-load the OEM charge circuit.

Keep in mind that unless you spend Big Bucks for a Balmar or ______ .... the average 100 amp alternator will cut back on the charge rate rather quickly.




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