Universal fog light harness install

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Jan 16, 2016 | 04:09 PM

RealityCheck

Thread Starter

Senior Member

Joined: Jan 2013

Posts: 355

From: Suffolk, NY

Universal fog light harness install

So I am wiring up a harness for my new projector fogs, but my question is related to the accessory wire. If the relay, and fuse on the harness is located near the battery, are you able to install the acc wire to a factory wire (cig lighter, radio, etc.) without it being dangerous? Common sense tells me it's okay because it only triggers it being on and off from ignition switch, but if the harness has a 30amp fuse, wouldn't that be a fire hazard if the factory accessories aren't rated that high? Didn't really find my answer through google. Sorry for stupidity.

Jan 16, 2016 | 06:52 PM

DennisMik

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Joined: Apr 2004

Posts: 10,644

From: Plano, TX

You do have a bit of confusion on this.

The 30 amp fuse is on the wire that goes to the battery. The other end of this wire goes to the relay and when the relay is energized, goes to the fog light lamps.

The trigger wire is used to energize the relay. This wire will have a low current on it, probably a fraction of an amp.

Code:

                         RELAY 
   ┌─────────┐        ┌──────────┐
   │         │        │  ▀▀▀▀▀▀  │
   │ BATTERY │    ┌───┼──O    O──┼──> TO DEVICE
   │         │    │   │          │
   │  -   +  │    ├───┼─/\/\/\/\─┼─┐
   └──┬───┬──┘    │   └──────────┘ │
      │   │       │                │
      │   │   ┌───┴──┐         ┌───┴────┐
      │   └───┤ FUSE │         │ SWITCH │
      ╧       └──────┘         └───┬────┘
   GROUND                          │
                                   ╧
                                GROUND


    - or - 

                             RELAY 
   ┌─────────┐            ┌──────────┐
   │   B     │  ┌──────┐  │  ▀▀▀▀▀▀  │
   │   A   + ├──┤ FUSE ├──┼──O    O──┼──> TO DEVICE 
   │   T     │  └──────┘  │          │  ┌────────┐
   │   T     │          ┌─┼─/\/\/\/\─┼──┤ SWITCH ├──> 12 volts
   │   E     │          │ └──────────┘  └────────┘
   │   R   - ├──────────┤          
   │   Y     │          ╧          
   └─────────┘       GROUND

Last edited by DennisMik; Jan 16, 2016 at 07:50 PM.

Jan 16, 2016 | 08:38 PM

RealityCheck

Thread Starter

Senior Member

Joined: Jan 2013

Posts: 355

From: Suffolk, NY

As I saw some diagrams on Google images, it does say it should be wired to 12v source, switched. I would be wiring to either fuse box with add-a-circuit or radio I guess. Wasn't sure whether that trigger wire needed to be wired into a source with the same amp rating.