C5: 12v+ power while cranking
Thread Starter
Instructor
Joined: Aug 2011
Posts: 243
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From: Kalamazoo Michigan
C5: 12v+ power while cranking
I'm looking for a small signal wire that keeps 12+ going to my head unit ACC wire while the car is cranking so my head unit can start booting up as soon as I put the key in and let the gauges sweep/fuel pump prime, and not reboot when it cranks. Anyone done something similar in a C5? Car is a '98. 
Tech Contributor
Joined: May 2003
Posts: 7,035
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From: North Augusta, SC
I'm not aware of a wire that would do that (doesn't mean it isn't there somewhere).
You could rig up a momentary pushbutton between B+ and radio trigger wire, then while cranking car just hold down the button for a few seconds. If you do that you might want to put a diode on the trigger wire so B+ only goes to the radio while you're pushing the button.
You could rig up a momentary pushbutton between B+ and radio trigger wire, then while cranking car just hold down the button for a few seconds. If you do that you might want to put a diode on the trigger wire so B+ only goes to the radio while you're pushing the button.
Thread Starter
Instructor
Joined: Aug 2011
Posts: 243
Likes: 11
From: Kalamazoo Michigan
Hmm, hadn't thought of a push button for that. I'd rather have it automatic. Maybe a small cap with a diode would be a good alternative. I just figured there had to be some wire with 12+ at one of the ECU pins or fuel pump.
Le Mans Master
Joined: Nov 2004
Posts: 8,718
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From: Dyer IN
Cruise-In IX Veteran
there are but they would be ignition wires and your radio would turn off when in ACC position. also the voltage drop may be so great during crank that the radio will reboot anyways
3rd Gear
Joined: Dec 2012
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That is the one thing that you may not be able to get-around. Otherwise, I would think that your only option would be to tap into the door chime circuit. I believe it is activated whenever a key is in the ignition, no matter the position. Theoretically, it would mean your stereo is on whenever a key is in the ignition. However, the voltage drop at startup could cause your stereo to reboot. Obviously wiring your radio directly from the positive post of the battery would eliminate that, but it would always be on, no matter the key position or whether or not there is even a key in the ignition.
Tech Contributor
Joined: May 2003
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From: North Augusta, SC
