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Distribution block for switched/constant 12V

Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=1126
Printed Date: July 25, 2025 at 12:51 PM


Topic: Distribution block for switched/constant 12V

Posted By: awd_sr
Subject: Distribution block for switched/constant 12V
Date Posted: June 04, 2002 at 7:04 PM

whats the best way to supply multiple components the switched and constant 12v?  For instance, if I want to hook up a set of fog lights, a stereo, an LED scanner... and I run them all to the same source, how can I guarantee they all get the power/current they need?  Thanks in advance



Replies:

Posted By: HotRod53F100
Date Posted: June 04, 2002 at 7:53 PM
In the case of the fog lights, you should never run them straight off of the switched source out of the fuse block. Wire the battery directly to a relay, out of the relay to the lights, and switch the relay coil by running the switched power to an off/on switch then to the coil. I would also include a fuse in line with the battery voltage feed to the relay. You can do the same with any high current draw accessory.  This way you are drawing straight off of the battery and using the switch on the low draw side. Fog lights are notorious for melting the off/on switch if you wire them directly. Even cheap fog lights are 55 Watts each. Thats 110 watts total, divide that into 12 volts and you have 9.2 amps. The 9.2 amps is the normal running amperage, the initial startup current will spike a lot higher.

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HotRod




Posted By: awd_sr
Date Posted: June 04, 2002 at 11:08 PM
thanks hotrod, so if the fog lights come with the relay installed in their harness, is that good enough protection?  Thanks again




Posted By: hot_shot_guy123
Date Posted: June 05, 2002 at 8:15 AM

Hot Rod is right.  I bought a set of Blazer Fog Lights, and the instructions had it set up to wire them directly to the battery without a relay.  I was wondering why there wasn't one but I figured maybe they didn't need one.  One day when I went to pull apart the panel where my radio is located, I could see that the rubber protectors for my wires on my switch were melted together.  I've changed the switch and added a relay and no more problems.  If it comes with a relay that's great if it doesn't then but one and wire it up like this.

Assumming that your using a 3 prong switch and the connections are, ground(black), switch(white), power(red)

PIN 85 = Ground

PIN 86 = On/Off wire from Switch (white wire)

PIN 87 = 12v constant fused

PIN 30 = Wire to foglights (white wire)



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"Light travels faster then sound, that's why some people seem bright until you hear them speak."
hot_shot_guy123




Posted By: awd_sr
Date Posted: June 05, 2002 at 10:32 PM
thanks hot shot, I'll go to Radio Shack to pick that up





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