So I have a question. I have an aftermarket stereo and when I crank the car the stereo shuts off as voltage drops to provide power to the starter (Totally get it).

My question is is there any fuse that I can tap into that stays on during crank? if so what is it.

I was debating putting a capacitor inline to provide the temporary power when this happens but am a bit hesitant.

Thanks again.

 

This isn’t due to your aftermarket radio. This is a feature that’s been on every car for decades. In order to always give full current to your starter, all non essential circuits are switched off during engine crank.

 

Power to the ECM is constant while cranking. If tapped into that circuit, the radio would stay on.

There are several power relays that either maintain power or drop power while cranking. Tapping into the right one is easy with the Electrical Test Manual (ETM) including all the wiring diagrams. Just make sure there is enough power (big enough fuse) on the circuit chosen. Probably could tap a power circuit at the engine bay fuse box.

 

Well i wound up doing this with capacitors and I get about 15-20 seconds of power and it works.

Diagram (Wound up only using 2 1000 capacitors and a one way diode

soldered and wired

bottom

shrink wrapped