Relay w/ Diode and Switch Wiring
Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=38250
Printed Date: May 15, 2025 at 1:52 AM
Topic: Relay w/ Diode and Switch Wiring
Posted By: SPOTTYJ
Subject: Relay w/ Diode and Switch Wiring
Date Posted: August 28, 2004 at 7:31 PM
Wiring gurus, request your assitance:
I will be installing a "Painless Cirkit Boss 3-Circuit Ignition Hot Fuse Block" from the battery into the center console of my Avalanche.
I plan on running an ignition switched wire to a relay so power only goes to my downstream electrical accessories (PS/2, DVD, Monitors, Power inverter, etc) when the IGN is on position only.
I would like to put a switch in this harness so my accessories only receive power when I activate the switch.
Where in line do I place the switch? I assume on the ignition source power supply prior to it connection to the relay? I think the relay works in that when it receives IGN power it will close the normally open relay allowing power to flow to the downstream accessories.
Also, how do I know what rating (amps) switch to use?
And would it be a good idea to install a diode along the ignition switch wire to protect the switch and IGN switched wiring? If so, I assume the diode would go between the relay and the switch?
How do I know what rating diode to get?
For those of you who have run wiring from your battery through your firewall, where is a good place to drill the firewall?
If you havn't guessed, I am a total wiring rookie.
I want to use the "Painless Cirkit Boss 3-Circuit Ignition Hot Fuse Block" so I do not draw to much from my factory wiring.
I will be powering a 12v DVD player and (2) headrest monitors and a 175 watt power inverter which will power a PS/2.
Thanks,
SpottyJ
Replies:
Posted By: SPOTTYJ
Date Posted: August 29, 2004 at 10:33 AM

This is how I understand the wiring to work. Not sure where to place a diode, and how to orientate.
Posted By: auex
Date Posted: August 29, 2004 at 1:19 PM
Do not use a diode, you probably won't find a large enough one for your situation. Also if you are using a switch to activate the fuse box, Then you will need a relay and this will isolate the ignition from the circuit.
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Posted By: mobilevt
Date Posted: August 30, 2004 at 2:37 AM
have you thought of using Power Tamers? Check copelandengineering.com under Power Tamer. I have many units left over from a project, they're awesome timer devices that keeps circuts on for a set time after the ignition is shut off. Sean ------------- Emergency Vehicle Technician
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Posted By: SPOTTYJ
Date Posted: August 30, 2004 at 8:50 AM
mobilevt wrote:
have you thought of using Power Tamers? Check copelandengineering.com under Power Tamer. I have many units left over from a project, they're awesome timer devices that keeps circuts on for a set time after the ignition is shut off. Sean
Thanks for the rply, looks like a cool product. However, I am not that interested in having my devices run after vehicle is off. My 03' Chevy Avalanche does have Retained Acesory Power (RAP), and that would provide 20 minutes of power after vehicle is off. I have already purchasd the circuit boss 3-way IGN fused harness. Had I not, I may have jump on your idea. I am stuck on the need, placement of a diode for protection of the IGN switched wire.
Posted By: mobilevt
Date Posted: August 30, 2004 at 9:03 AM
If the ignition serves as a trigger for the relay, you can use as low as 1a but I always use 3a because it's a little bigger and not prone to breakage. Sean ------------- Emergency Vehicle Technician
Got Freedom? Thank a vet!
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