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]

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]

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]

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]

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. :redface: Hence my desire for it to cycle off when the ACC buss is off.

[Tamago]

I can see myself forgetting to turn it off someday and returning to a dead battery. :redface: 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]

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]

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! :smile: 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]

Ahh - now we're getting somewhere. Thanks! :smile: 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.





25808

[BailOut]

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]

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]

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]

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.

[BailOut]

Tamago,

Another great but ineffective idea. :frown: The problem is that the ACC bus is cut out by the ignition key's rotation long before the starter solenoid is active. You can see this by turning your key to the on position and waiting for your stereo to power up, then slowly cranking the key towards the Start position.

My own wiring idea in the first post doesn't work, either. What I'm going to need to do is hook the stereo's power up to a line that maintains power during a start. I know the brake lights and ECU retain power during a start, but the brake lights are powered at all times and I am wary of tapping into the ECU's power supply.

Does anyone have other ideas, please?

[CTScott]

OK. I see that now. When the keyswitch moves from on to start the ACC feed is switched to the IG1 feed.

How about jumping ACC (white in pin 2) to IG1 (green in pin 1) at the keyswitch? That way regardless of the keyswitch position ACC will be energized.

[BailOut]

OK. I see that now. When the keyswitch moves from on to start the ACC feed is switched to the IG1 feed.

How about jumping ACC (white in pin 2) to IG1 (green in pin 1) at the keyswitch? That way regardless of the keyswitch position ACC will be energized.
Thanks for another great idea, CTScott, but jumping pin 1 to pin 2 on the key switch did nothing. :frown: No change at all. I also tried removing the ACC cut relay with the jump in place, which doesn't even allow the stereo to turn on at all. I also tried jumping pins 3 and 4 on the ACC cut relay while leaving the key switch jump in place, which allows the stereo to turn on but still allows it to be killed when engaging the starter.

This is turning out to be one bugger of a problem!

[CTScott]

Hmmmmmm.

Try jumping ACC (white pin 2) to IG2 (pink pin 6) instead.

You will still need the ACC cut relay bypass (jumpering 3 to 4) in place, as the ACC cut relay is between the keyswitch and the radio.

[eTiMaGo]

Would bypassing the whole ACC cut system be detrimental to the accessories/starter? I mean, there's a reason why this system exists, right?

If so, I'm not sure how you would wire this up exactly, but you could use the power from the START position to compensate for the "hole" of the ACC cut, only for the radio, if you know what I mean.

[CTScott]

Would bypassing the whole ACC cut system be detrimental to the accessories/starter? I mean, there's a reason why this system exists, right?

If so, I'm not sure how you would wire this up exactly, but you could use the power from the START position to compensate for the "hole" of the ACC cut, only for the radio, if you know what I mean.

His original intention was to just slip power in during the "cut". This is possible, but would require a relay and a diode. When researching the "cut" circuit I found that the sole purpose of the circuit is to keep things from flickering, as opposed to protecting the starter.

[BailOut]

Hmmmmmm.

Try jumping ACC (white pin 2) to IG2 (pink pin 6) instead.

You will still need the ACC cut relay bypass (jumpering 3 to 4) in place, as the ACC cut relay is between the keyswitch and the radio.
This was a difficult one to pull off due to the IG2 wire being a much smaller gauge than pins 1 and 2, but I got 'er done. Still no change. :frown: The stereo and instrument panel still cut out during a start.

Thank again for feeding me ideas, though.

[CTScott]

Check the voltage on IG1 and IG2 to ground during starting. I am 99% sure that either or both of them remain hot during starting.

If that is the case, then tap from there directly to the radio's switched power input (Grey wire in pin 3 of the OEM harness).