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2004-2008 Mazda3

Flex Innovations Big3 Grounding Kit Walkthrough

The F.I. Big3 = Engine to Chassis, Negative Battery to Chassis, Alternator Positive to Battery Positive.  (Power Wire is Fused with 150AMP Wafer)

Basic Tools:  Metric Socket set. (Especially 10mm & 12mm)


Instructions:  First organize the Wires from Shortest to longest.  The shortest wire is “Wire1”, the second shortest wire is “Wire2”, and so on till you have the longest wire which is “Wire4”.

For safety purposes, you may want to disconnect the negative battery post for the installation of the grounding kit.




Wire1 = Battery Positive (Bolt P) to Wafer Fuse


Wire2 = Battery Negative (Bolt B) to OEM Chassis (Bolt C)


Wire3 = Rear Engine Hanger (Bolt D) to OEM Chassis (Bolt C)


Wire4 = Wafer Fuse to Alternator Positive (Bolt A)


Note: First connect wire 1 to the fuse and then wire 4 to the other end of the fuse.  The other end of wire 1 will connect to the positive battery terminal.  The other end of Wire 4 will connect to the positive alternator terminal.  (This is called Wire 1 + Wire 4)


Note: There are 2 unique ring terminal sizes.  The largest ring connects to the engine hanger.  The smallest ring connects to the negative battery.


Alternator Connection Point

Unhook the plastic cover and unscrew the bolt from the Alternator.  This is where the end of your longest Wire4 will connect.  The other end of Wire4 will connect to the Fuse.  The fuse will then connect to Wire1 which connects to the POSITIVE battery terminal.

After you’ve connected the wire to the Alternator the OEM plastic housing will not fit without modification.  You may wrap the bolt and connection with Electrical tape to keep out contamination and moisture.

WIRE 4 - Alternator Connection (Bolt A):


When you attach Wire4 to the alternator, remember to KEEP the OEM wire that is already attached to the alternator as is.  Notice in the picture above, there are TWO wires connected to the bolt.  The OEM wire goes UP and the big3 wire goes down.  You will have to modify the plastic protector piece with a grinding tool if you want to keep it.  I suggest using a quality electric tape to FULLY waterproof the connection and not using the plastic piece at all.

 WIRE 1 – Battery Positive (Bolt P):

WIRE 2 - Bolt B (Neg. Bat.) to Bolt C (OEM Chassis)

Route wire 2 down through the battery box and to location "C".  By doing it this way you will not have to cute a hole in the side of the battery box.

Wire 3 = Bolt D (Engine Hanger) to Bolt C (OEM CHASSIS)


This wire routes along the top of the firewall as seen in the picture above.  Make sure that there's enough slack for some engine movement because this wire is an engine block ground.  Point "C" connects to the existing OEM ground.

Note: Some people "CLEAN" their oem grounding point with a wire brush and scratch off some of the paint where the OEM grounding point makes contact with the chassis. I have found that the connection to the chassis is mostly due to the threaded area, however please feel free to improve upon the factory grounding point.

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Last modified: 03/24/10