simple switch with relay

Hello all, first post in this forum...

I have a Pioneer Avic z110BT installed in my truck that is wired conventionaly to power up when the key is in accessory mode. My beef is that if I stop the truck and leave it accessory it stays powered up but once I turn the key to restart it reboots. That got me thinking about wiring up a switch to toggle the power source for the deck between accessory and constant battery. This way I could not only keep the unit up until the truck restarts but I could run the audio system without a key (like when camping or at the beach).

This quick diagram represents what I think I can do easily but I'm not sure If I will need diodes to protect anything or a capacitor to maintain voltage during the switch.

Thoughts and comments?

Just power the unit straight from the battery (via a fuse!) - that's what I do.
And that is effectively what you have - except worse... ie, why switch from the battery to the "dirty" IGN +12V or ACC supply, and why suffer the momentary drop in supply when switching and cranking?

(I used to have a selector switch, but what's the point?)

The AVIC units don't power down like conventional units so running them constant all the time won't work. I made the point above - I want choice.

Does anyone else have anything useful to contribute?

Well Mr Narky, sorry I misunderstood.

I'd suggest an SPST relay with diodes (IN4004 etc) from the ACC & IGN to 86 so that it doesn't drop out when cranking, and the +12V switch also thru a diode to 86. Then fused battery to 30 (and the switch) and 87 to the Pioneer.
You then have un-glitched power on ACC & when cranking, and whenever you want it on otherwise.

i dont see why you need a relay at all, just run a switch in between the red and yellow wire behind the radio. when you have the switch on it will stay on and when you have the switch off it will turn function normally with the key.

the relay diagram you have posted makes no sense because with 12v on 85 and ground on 86 the relay will just stay on all the time

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oldspark wrote:

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Well Mr Narky, sorry I misunderstood.

I'd suggest an SPST relay with diodes (IN4004 etc) from the ACC & IGN to 86 so that it doesn't drop out when cranking, and the +12V switch also thru a diode to 86. Then fused battery to 30 (and the switch) and 87 to the Pioneer.
You then have un-glitched power on ACC & when cranking, and whenever you want it on otherwise.

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I didn't think you guys down under were so easily ruffled. I appreciate the follow up and hadn't considered you idea. I will look at it tonight.

soundnsecurity wrote:

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i dont see why you need a relay at all, just run a switch in between the red and yellow wire behind the radio. when you have the switch on it will stay on and when you have the switch off it will turn function normally with the key.

the relay diagram you have posted makes no sense because with 12v on 85 and ground on 86 the relay will just stay on all the time

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I prefer a relay for piece of mind. The switch on 85 interrupts the 12v power.

Oldspark - is this what you are suggesting?

Not ruffled, but I have no idea what a Pioneer Avic z110BT is.
And if it can't tolerate the relay's switching time...


Yes, that diagram is correct but it is one diode each for the ACC and IGN - ie, 3 diodes in total.

You might also be able to relay off of the keysense wire, since that wire doesnt change while turning. Key in, radio on.

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To master and control electricity is perfection. *evil laugh*

racerjames76 wrote:

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You might also be able to relay off of the keysense wire, since that wire doesnt change while turning. Key in, radio on.

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Good one. I'll look into that.