Keep radio on during engine start?
2nd Gear
Joined: Apr 2021
Posts: 2
Likes: 1
The most efficient method would be to use a 1000uf 25V capacitor, 1K resistor and diode.
Cut the ACC wire from the OE (or aftermarket) harness.
Wire the resistor and diode in series to the + of the capacitor.
Solder the ACC (vehicle side) before the resistor/diode going to the + cap.
The radio ACC wire get soldered after the resistor diode closest to the + leg of the cap.
Finally ground the - lead of the cap.
-------------- R - ------- D ----------------- --- + C - --
Car ACC ---/\/\/\----[ ||]----(Radio Acc)------|(-----(Gnd)
For any relatively modern radio (OEM or aftermarket) a 1000uf cap is sufficient for 5-8 sec which should be plenty for normal cranking.
A greater uf cap will work too though IMO 1500uf at max or it will keep the radio on a little too long.
Resistor isn't necessarily required but used to protect the diode & cap from the initial in-rush current while it charges.
A 16V cap will work in a pinch but is cutting it close to charging voltage so 25V or greater is recommended.
Cut the ACC wire from the OE (or aftermarket) harness.
Wire the resistor and diode in series to the + of the capacitor.
Solder the ACC (vehicle side) before the resistor/diode going to the + cap.
The radio ACC wire get soldered after the resistor diode closest to the + leg of the cap.
Finally ground the - lead of the cap.
-------------- R - ------- D ----------------- --- + C - --
Car ACC ---/\/\/\----[ ||]----(Radio Acc)------|(-----(Gnd)
For any relatively modern radio (OEM or aftermarket) a 1000uf cap is sufficient for 5-8 sec which should be plenty for normal cranking.
A greater uf cap will work too though IMO 1500uf at max or it will keep the radio on a little too long.
Resistor isn't necessarily required but used to protect the diode & cap from the initial in-rush current while it charges.
A 16V cap will work in a pinch but is cutting it close to charging voltage so 25V or greater is recommended.
Last edited by Sereno011; Apr 15, 2021 at 04:22 AM.
