avoid stereo dropout during crank

I've been working on a remote starter for my 2001 Honda Civic EX when an idea popped in my head. Have the stereo run through cranking. I set up a relay system like so: 30: 12V constant (ignition harness) 85: 12V constant (ignition harness) 86: Keysense (ignition harness) 87: Secondary Accessory (ignition harness) 87a: Open The relay worked almost exactly as I wanted. The radio starts as soon as the key is inserted, but it still cuts out during cranking. At first, I thought that I should set up a new circuit specifically for the stereo (which is why I initially came here). Now, I'm again wondering why it doesn't work through crank, as the remote starter is using the same wire for power, and that works just fine. Is it possible that the keysense wire cuts out when cranking? I can't think of any other reason. Would setting up a system like this work safely? 30: Starter wire (located at the ignition harness. This would then be fused to 7.5 A to ensure the radio does not fry. However, I'm not sure whether or not the fuse would burn out the second the key goes to crank. I don't know the exact amperage of the starter wire, but I'm sure it's above 7.5 A.) 85: Starter wire (ignition harness) 86: Ground 87: Secondary Accessory (ignition harness) 87a: Open Thanks.

Connect the red wire of the radio to the Ignition wire instead of the accessory wire.

If you listen to the stereo with the key in the acc position, and you do not want to lose that ability, use 2 diodes and supply the red wire of the radio with both Acc and Ignition feeds.

I ended up changing pin 87 from Secondary Accessory to the red wire from the radio (I've tested to make sure this is power input. It's red because it's an aftermarket system). It still power cycles during crank, though. I've tested to make sure that power is going all the way through, and it is. I found the wiring for a 2001 Honda Civic radio: https://www.the12volt.com/installbay/forum_posts.asp~TID~35520. What is the radio switch wire? Can that wire turn the radio off while cranking?

I assumed you had an aftermarket radio.  The Switched wire of your OEM radio is Yellow/Red.  Do the lights go out on the deck during startup, or do you just lose sound?

Lights and sound go out. Here's what I did: after following the stereo's wires to the original wires, I found out that the red wire I tapped into was actually the original yellow/red radio switch wire. I tested the original radio switch wire through all stages of key turns. It drops during crank. But I've cut the wire and connected it to pin 87, so it's getting power all the way through. I also tested the original 12V constant wire, but this shows 12V (with a drop to about 10V) even through crank. Can the voltage drop (during crank, my multimeter shows a drop from roughly 11-12V to around 10V) cause the radio to shut off?

i am an idiot wrote: Connect the red wire of the radio to the Ignition wire instead of the accessory wire. If you listen to the stereo with the key in the acc position, and you do not want to lose that ability, use 2 diodes and supply the red wire of the radio with both Acc and Ignition feeds.

i like this idea, would 1 amp diodes be enough? im gonna try this on my f150 and my 2004 silverado, however do you think it would work on the silverado seeing as it uses data @ the interface for an switched accessory output? i would just bypass the interface and grab the ACC and IGN leads a column but i have heard mixed results bout doing this on GM trucks, any thoughts?Go BIG or go Home                                    it might not be broke, but lets fix it anyway

If it were an aftermarket deck, then yes a 1 amp diode would work fine.  I do not know if the OEM deck uses the switched wire just as a voltage sense wire.  If you use a 470 Microfarad capacitor, and the 1 amp diodes, and it works, then the 1amp diodes will be fine.  If you have to up the capacitor to 1500 Mic, you should use a 6 amp diode.

I was thinking that a capacitor might work but didn't know what rating would be needed. How can I figure that out? Or perhaps the usual 470mf is enough?