Strange Plug, purpose???

[mleads310]

Removing my 05 f250’s (unfortunately had a hole above thermostat housing and by time I realized intake ingested water and hydro locked) mechanical controls , installing 08 f250’s with DEC. I was removing old harnesses and
I came across this single plug that was connected to the port motor and runs back to the battery switch (1/2/both/off). I’m kind of curious what the purpose of this plug was for and why it’s only hooked up to one motor and do I need it going forward with a newer install?

Any help is appreciated

 

[cap]

Looks like the battery charging wire for a second battery.

 

[mleads310]

Would there be any reason someone would hook this up directly to the on off battery switches on a sailfish?

 

[SkunkBoat]

In a single motor configuration, it would charge the "2" battery while the switch is on "1". You would not have to use the switch to alternate batteries to keep both charged.
Everyone with a single should use this....


In a "factory" twin setup, there are two battery banks and two switches.
Usually Bank 1 is a pair of batteries in parallel and "normally" is connected (stb switch on position 1)to the STB motor and the HOUSE
+12V. The Stb motor starts from bank 1 and charges bank 1.
The Port motor is connected to Bank 2 thru the Port switch on position 2. The port motor starts from Bank 2 and charges Bank 2.
( the switches allow you to reverse banks & motors)

Using an Aux charging cable would allow charging of both banks by one motor. So in your case, if the port charging cable was connected to terminal 1 of either switch, it would charge the "Stb" Bank 1 along with the Stb motor. If the stb motor was off, the Bank1 (House) would still be charging.


The other way to use Aux Charging cables is to separate the HOUSE into a third BANK 3 of batteries. Charge it from both motors using two Aux cables.
Then your motors each have a dedicated start battery and the House always charges. You can then also use Deep cycle batteries for the House.
You will never again run down a start battery with your 2500W stereo amp & 17 speakers.

 

[mleads310]

Thank you for the detailed explanation. Definitely makes sense now. It’s pretty interesting and would have never know if I hadn’t been doing a report.