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Keeping Power On to Alpine Head Unit Through Crank


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rotohead 
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Posted: January 19, 2020 at 5:58 PM / IP Logged Link to Post Post Reply Quote rotohead
Have a 1998 Dodge Ram diesel and I hate it when starting you turn the key to 'run' then 'wait to start' (none of that is a problem) but then when turning to crank the power is cut to the Alpine and it is forced to reboot and start all over. Is there a way by using capacitors and other things to keep the Alpine powered(and maybe other things like gauges). I got to think rebooting the head unit halfway through initializing is not good for it esp when it happens every time you start the vehicle. It is a computer after all. I'd appreciate a wiring diagram and parts necessary to do this greatly.
i am an idiot 
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Posted: January 19, 2020 at 9:42 PM / IP Logged Link to Post Post Reply Quote i am an idiot
A 3 amp diode and a 3300 microfarad (at least 25 volt) capacitor. Insert the diode between the truck switched wire and the radio's red wire. Banded end of the diode toward radio. Positive lead of the capacitor connects to the banded end of diode. Ground the capacitor's negative lead.
I have not done this in a long time. If you are having to order this stuff, maybe get 2 of the capacitors. If the on time is not long enough, parallel the second capacitor with the first one.
i am an idiot 
Platinum - Posts: 13,288
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Posted: January 19, 2020 at 10:08 PM / IP Logged Link to Post Post Reply Quote i am an idiot
If you have access to two 1 amp diodes you can do this instead, Same diode configuration as listed above. A second diode banded end to the banded end of first diode. Other end of that diode to the Dk. Blue ignition wire at the key cylinder.
rotohead 
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Posted: January 20, 2020 at 12:13 PM / IP Logged Link to Post Post Reply Quote rotohead
Thank you very much for the reply. I'm not a electronical engineer so describing the process the way you did is much appreciated. The power off time is very short on these Cummins engines. I'd say less then 3 seconds. I bought a assortment of capacitors and diode on Amazon so I should be able to get something to work. Now to get lucky and dust off my old soldering skills...and not start my truck on fire. Thanks again 'i am a idiot'
EDIT: I got this wired up and installed today and it works perfectly. Thanks again IAAI
i am an idiot 
Platinum - Posts: 13,288
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Posted: January 21, 2020 at 5:33 AM / IP Logged Link to Post Post Reply Quote i am an idiot
How much capacitance did you use?
rotohead 
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Posted: January 21, 2020 at 11:44 AM / IP Logged Link to Post Post Reply Quote rotohead
i am an idiot wrote:
How much capacitance did you use?
I timed the power off time and it was 1.5 seconds. I used a 4700uf 50 volt capacitor. When I turn the truck off the Alpine stays on for 4 seconds so I think I have enough storage to make it work long term.
rotohead 
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Joined: January 19, 2020
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Posted: May 17, 2020 at 4:47 PM / IP Logged Link to Post Post Reply Quote rotohead
Well, that didn't last very long. I'll have to dig into the dash when I have time but it seems the capacitor failed.
i am an idiot 
Platinum - Posts: 13,288
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Posted: May 18, 2020 at 3:54 PM / IP Logged Link to Post Post Reply Quote i am an idiot
Highly unlikely. Maybe a broken leg, but I doubt the cap failed.
rotohead 
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Posted: July 18, 2020 at 4:24 PM / IP Logged Link to Post Post Reply Quote rotohead
Well I'm highly confused. The capacitor/diode assembly worked perfectly for 3-4 months in my truck then failed. I removed it, tested and couldn't find anything wrong with it. I made a new one identical to the first and it won't work either. Tried a couple different capacitors of various sizes and nothing. Sooo, I'm going to try the '2' 1amp diode configuration suggested in the third post and see if that works. Very frustrating. Glad I choose a career other then electrical related.
i am an idiot 
Platinum - Posts: 13,288
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Posted: July 18, 2020 at 8:57 PM / IP Logged Link to Post Post Reply Quote i am an idiot
Post a picture of the caps and diode installed on the wire.
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