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need to switch 12volt constant hot

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=107246
Printed Date: July 15, 2025 at 2:57 PM


Topic: need to switch 12volt constant hot

Posted By: autocraf91162
Subject: need to switch 12volt constant hot
Date Posted: September 05, 2008 at 9:44 PM

to power off with ignition of 2004 bmw 7 series



Replies:

Posted By: KarTuneMan
Date Posted: September 06, 2008 at 12:05 AM
What???

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Posted By: KPierson
Date Posted: September 06, 2008 at 8:11 AM

As long as the load is less then 30A you can use a standard 30A Bosch style automotive relay.

Connect Pin 85 to ignition source
Connect Pin 86 to ground

Connect Pin 30 to constant 12vdc
Connect Pin 87 to your device that needs constant power only when the ignition is on.

Alternatively, if your power requirement is small enough you can just tap directly in to the main ignition wire of the car.

What exactly are you trying to do?



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Kevin Pierson


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