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Kodysteeler43 01-19-2010 06:06 PM

Fog Light Trouble
1 Attachment(s)
I have two fog lights on my bumper. My pap hooked them up. They worker for about two weeks then suddenly stopped. The left light turns on when the switched is somewhere in the middle and the right never even flickers. Is this the wiring or the switch?


Beachcomber 01-19-2010 06:28 PM

Did you use a relay or did you wire them directly to the switch? If you wired directly to the switch you could have fried the switch.

HyperBuzzin 01-20-2010 07:53 AM


Originally Posted by Beachcomber (Post 526790)
Did you use a relay or did you wire them directly to the switch? If you wired directly to the switch you could have fried the switch.

Sounds to me like your Pap didn't use a relay.

Kodysteeler43 01-20-2010 04:36 PM

3 Attachment(s)
idk what a relay is but there is a wire hooked to the battery and then pops out in the steering column with a positive and negative wire.

Atthehop 01-20-2010 04:48 PM

Relay Wiring
You should allways wire extra lights and stuff using relays. Here is how they should be wired.

Tis wall save your switches and the harnesses from frying.

Kilroy 01-20-2010 06:13 PM

Use a relay if the lights or other load draws more amps than 0.75x the switch Max. Amps. And make sure the wires are big enough for the amps.

s3nt3nc3d 01-20-2010 06:30 PM

i = w/v

i = amp draw
w = watts
v = voltage

So given that formula...

i = 110 (2 55w fog lights--estimated) / 12 volts

i = 9.2 amps

Am I correct in that calculation aside from estimating the fog light wattage?

So a switch rated at 15+ amps should be able to carry that load, wouldn't it? ...possibly up to a 30amp switch if they are high powered bulbs.

Kilroy 01-20-2010 07:01 PM

Just do not rapid cycle the switch. This is also true for relays.

Beachcomber 01-20-2010 07:27 PM

Your calculation is correct but you need to take into consideration line loss. The longer the distance the more loss and the current draw becomes larger. DC voltage has a lot of line loss. When you use a relay you should place the relay as close to the battery and as close to the lights as possible to keep the loss to a minimum.

Jerry Bransford 01-20-2010 07:31 PM


Originally Posted by Beachcomber (Post 527544)
DC voltage has a lot of line loss.

More than AC voltage line loss? ;)

Beachcomber 01-21-2010 07:18 AM

Much more, that's why your home and the country uses AC voltage. If we had to wire for DC our homes would have wires the size of your plumbing pipes.

Kilroy 01-21-2010 07:44 AM

Long lines dissapate some of the energy going to the load. If the line is too long, or the wires too small, the lights will not be as bright. If the wires are way too small, they will get hot and could cause a fire. This is true for AC and DC current.

Household wiring is 10x the automotive 12V, so it takes 10x less current to produce the same power.

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