Request for help: diagramming a relay

[BailOut]

In order to work around the issues I'm having with my Pioneer AVH-P3100DVD head unit always prompting the OK screen when the unit is restarted while viewing a DIVX file, and often failing to restart the audio at that time, I am pondering using a relay to keep it powered as long as the 12V accessory bus is powered up but having it draw power directly from the battery rather than the accessory bus.

I think I can do this with a standard 5-pin SPDT automotive relay but would like confirmation. I would wire it as such:

30: fusable link to radio's ACC line
85: ground
86: fusable link to 12V battery
87: not used
87a: fusable link to 12V accessory bus

Would that work?

And would it be enough, or would I need to yank the "ACC Cut Relay" as well?

[Tamago]

if your installer wired your radio properly you shouldn't have this problem. there is a 12V constant already in the wiring harness AT the radio. this is what keeps the radio memory intact.

[BailOut]

Originally Posted by Tamago

if your installer wired your radio properly you shouldn't have this problem. there is a 12V constant already in the wiring harness AT the radio. this is what keeps the radio memory intact.

This is not an issue with the radio's memory but with it being power cycled when a key start occurs. This is its expected behavior as the whole accessory bus is cut out during a key start.

I am attempting to bypass that by drawing power directly from the battery but only when the 12V accessory bus is powered (so that it will turn off when I turn the key to the off position).

I installed it myself, btw, and it works as intended. Now I'm trying to take it beyond what was intended.

[Tamago]

the constant wire at the radio is just that. constant.

you don't need to do this at the battery.

[BailOut]

Originally Posted by Tamago

the constant wire at the radio is just that. constant.

you don't need to do this at the battery.

Good point, but that only changes one connection point on the relay. A way for it to cut out when the accessory bus is not in use is still needed.

[Tamago]

Originally Posted by BailOut

Good point, but that only changes one connection point on the relay. A way for it to cut out when the accessory bus is not in use is still needed.

diode between ACC bus and radio feed.. wait nevermind haha...

why not simply shut off the stereo every time you're done using it? or does it still lose its position if you do this?

[BailOut]

Originally Posted by Tamago

diode between ACC bus and radio feed.. wait nevermind haha...

why not simply shut off the stereo every time you're done using it? or does it still lose its position if you do this?

I can see myself forgetting to turn it off someday and returning to a dead battery. Hence my desire for it to cycle off when the ACC buss is off.

[Tamago]

Originally Posted by BailOut

I can see myself forgetting to turn it off someday and returning to a dead battery. Hence my desire for it to cycle off when the ACC buss is off.

no, i mean shut it off now, don't change the wiring at all. if it's "off" it should retain the settings thru the constant wire, as opposed to resetting while it's in ON and loses ACC power, right?

[BailOut]

Tamago,

I appreciate you trying to help but you're quite far off the mark and don't seem to understand what I'm trying to do here. I asked for help with diagramming a relay so let's stick to that, please.

[Tamago]

Originally Posted by BailOut

Tamago,

I appreciate you trying to help but you're quite far off the mark and don't seem to understand what I'm trying to do here. I asked for help with diagramming a relay so let's stick to that, please.

BailOut, i understand fully what you're trying to do, and i don't appreciate it in the least. I'll hunker down and be helpful now.

[Tamago]

30: common to battery 12V
87: common to "stereo power wire"
85: common to "starter solenoid 12V"
86: common to GROUND.
87a: not used

so, only when the starter solenoid is engaged, the relay is in operation. because you're using 87 (NO contact) you won't be powering anything when the key is turned off. and because you've hooked 30 to "constant" your ACC circuit will be backfed power directly from the battery during the "start" cycle. since the ACC circuit does not power high-draw items such as the windows or AC or fan or defrosters, you should not have an issue with battery draw during the "start" cycle.

sound good?

also, this can all be done right at the radio (no need to run a feed from the battery itself)

[BailOut]

Originally Posted by Tamago

30: common to battery 12V
87: common to "stereo power wire"
85: common to "starter solenoid 12V"
86: common to GROUND.
87a: not used

so, only when the starter solenoid is engaged, the relay is in operation. because you're using 87 (NO contact) you won't be powering anything when the key is turned off. and because you've hooked 30 to "constant" your ACC circuit will be backfed power directly from the battery during the "start" cycle. since the ACC circuit does not power high-draw items such as the windows or AC or fan or defrosters, you should not have an issue with battery draw during the "start" cycle.

sound good?

also, this can all be done right at the radio (no need to run a feed from the battery itself)

Ahh - now we're getting somewhere. Thanks! That sounds like a solid idea.

Though it can all be done "at the radio" where would I tap into the "starter solenoid 12V" line? From the engine compartment, I presume?

[Tamago]

Originally Posted by BailOut

Ahh - now we're getting somewhere. Thanks! That sounds like a solid idea.

Though it can all be done "at the radio" where would I tap into the "starter solenoid 12V" line? From the engine compartment, I presume?

i don't know the actual yaris wiring diagram so i won't say what i think is the obvious answer (at the ignition itself). for all i know the yaris uses sinking switches instead of sourcing to send the "start" signal.

[CTScott]

How about just eliminating the ACC cut relay and jumping the output contact terminals? The service manual says that its purpose is just to keep the clock and meter from flickering during cranking.

You could use a jumper wire with male spade terminals. Jump 3 to 4.





ACC Cut Relay.jpg

[BailOut]

Originally Posted by CTScott

How about just eliminating the ACC cut relay and jumping the output contact terminals? The service manual says that its purpose is just to keep the clock and meter from flickering during cranking.

You could use a jumper wire with male spade terminals. Jump 3 to 4.

That sounded like a great and simple idea but it did not work. I jumped 3 to 4 to no effect. The interesting thing is that the clock works just fine (no flickering) with or without the ACC cut relay or 3-4 jumper in place.

Thanks for trying, though. Tomorrow afternoon I'll try wiring in a relay.

[CTScott]

Originally Posted by BailOut

That sounded like a great and simple idea but it did not work. I jumped 3 to 4 to no effect. The interesting thing is that the clock works just fine (no flickering) with or without the ACC cut relay or 3-4 jumper in place.

Thanks for trying, though. Tomorrow afternoon I'll try wiring in a relay.

Try 3 to 5 then. I wasn't sure if the NO or NC contacts were being used.

[BailOut]

Originally Posted by CTScott

Try 3 to 5 then. I wasn't sure if the NO or NC contacts were being used.

I thought of the same based on the diagram you attached but pin 5 isn't used in the ACC cut relay's socket. It's an empty space.

[CTScott]

Originally Posted by BailOut

I thought of the same based on the diagram you attached but pin 5 isn't used in the ACC cut relay's socket. It's an empty space.

OK. That makes sense - The EWD shows 3-4 being the contacts.

If you put a voltmeter on the power wire, do you actually see it still cut out with the jumper in place (or just sag to below 12V)?

Looking at the EWD, with that jumped, power should definitely still be applied to ACC during cranking.