why does this switch blow fuses?


New Member
Jul 1, 2010
I hooked up a new rocker arm style 30amp switch that illuminates when the power is on.

when i disconnect the extra ground wire (for the switch illumination) and just the leave the incoming and outgoing power wires hooked up, the switch functions fine.

but when i connect the ground wire for switch illumination, the 30 amp in-line fuse always blows when i cut the switch OFF. it blows when i turn the power OFF, not ON. seems strange to me.

to clarify, there are 3 labels on this switch. "load" and "supply" which are the incoming and outgoing wires for the actual lights that the switch operates, and "earth" which is for the ground wire for the switch illumination to function. do i have those correct?




Lifetime VIP Donor
May 21, 2010
NW Indiana
"Load" needs to be the outgoing wire: the one that runs to the item you are switching on or off.

"Supply" needs to be the incoming wire: the one that runs to the battery or breaker or fuse block.

Turning the switch on connects the load terminal (at the center of the switch) to the supply terminal (on the left end of the switch, let's say).

Turning the switch off connects the load terminal (at the center of the switch) to the ground terminal (on the right end of the switch, let's say).

This works fine normally, as it shunts the load to ground when the switch is off. However, when you swap the "load" wire with the "supply" wire, you are shorting your wire that runs to your battery straight through the fuse to ground.

In short: try swapping the "load" and "supply" wires and see what happens.

Andy L.

Jun 16, 2010
Not sure if you just typed it backwards or if you have these two confused....

Load = outgoing from switch(power to light)

Supply = incoming to switch (power from battery)

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