wiring harness


Old 01-01-10, 10:28 AM
Thread Starter
Join Date: Dec 2009
Location: ri
Posts: 8
Received 0 Votes on 0 Posts
Question wiring harness

I have a 2005 toyota corolla with (no wiring harness in the car) for the new fog lights i purchased. The kit contains lights, switch, relay, and wiring harness. The relay has 4 wires 1black, 1blue, 1red, and 1purple and the fuse taped to the harness. The switch has 4 wires 2red, 1black and 1blue wire. Can anyone walk me through the wiring setup, I somewhat have an idea of the setup. Thanks Sammy
Old 01-01-10, 12:16 PM
HotxxxxxxxOKC's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Jul 2006
Location: USA
Posts: 8,034
Received 0 Votes on 0 Posts
Are these OEM fogs?................................
Old 01-01-10, 02:33 PM
Join Date: Oct 2008
Posts: 1,312
Received 0 Votes on 0 Posts
I'm not paying attention to what color wires you have, I'm using my own colors in the following...

A relay is just a switch.

The only thing is the relay-switch is activated with electricity.

You use a relay to switch power to larger wires which are best kept under the hood. One example is the starter which has very large wires. It would not be easy to run those large wires up the steering column to the key switch!

So they use a relay or solenoid which is the same basic thing.

So just install the lights, install the relay under the hood. Best on the firewall or side where it will get good air flow. Relays can get to be quite hot if they are activated for a long time.

Then you would connect a red wire to the battery positive (+) or a main connection point for all the positive wires in the vehicle. And the power going to the fog lights via the relay switch contacts would typically use a larger wire.

Right after the connection to the battery positive connection, there should be a fuse. This protects the battery and the other wiring in your car.

Then connect the red from the battery to one relay switch contact. Then from the other relay switch contact, another red wire would go to the fog lights + or positive.

Then the other wire on the for lights (black typically) would go to a good ground (-) on the body.

Now if you apply + and - to the relay "coil" connections, this will make the relay switch on and the fog lights should come on!

How a relay works...
HowStuffWorks "How Relays Work"

Then mount the switch where you want it inside the vehicle. One side of the switch needs to go to positive. You could tap into another circuit like the cigarette lighter and this would already be fuse protected. Or you could run another wire to the battery or positive distribution and fuse that wire.

Then the other connection on the switch would go to one coil connection on the relay. The other coil connection would go to body ground (-).

Now you flip the switch, and it causes the relay to turn on. This in turn causes the fog lights to turn on.

Next is to wrap all wiring with black electrical tape, then cover all wiring with that black plastic tubing. This protects the wiring from rubbing against a sharp metal object and grounding out.

Next install tie wraps all over to place to keep the wiring from moving. Again so it can't rub back and forth against a sharp metal object and that slice through the wiring and short out.

Basically make the wiring job look like the factory wiring. The factory wiring is well protected for good reason!

Thread Tools
Search this Thread
Ask a Question
Question Title: