Headunit install electrical query - Calling all electronic guru's

[Thirteen13]

Hey Guys,

Sorry in advance if this is the wrong section, i was unsure which was correct one ? Plus im bit noob at this stuff!

Ive just purchased a Pioneer AVH-P4450. So basically Double din touchscreen DVD headunit which is 2012 model.

I've wired it all up using one of those lovely $15 repco harness so keeps the car harness all clean and tidy.
Currently its the deck running off the stock wiring and stock speakers and in 2000 celica it sounds quite good.

Down the track however im going to be switching to a proper amp and 4 aftermarket speakers. So with this in mind, I currently dont have the "handbrake" wire connected as i want to bypass it. I understand you need 4 pin relay and you basically ground out the relay, supply the "green" handbrake wire to one side of the relay and use the blue/white amp power wire to supply the power.

However my query comes from that fact that at the moment the power source will feed the relay only. But down the track when i want to wire in an amp, I want to know the wiring setup and if it will still work fine. Ive read that the Amp wire runs very low power and its purpose is to signal to the amp to switch on. However drawing some of that power to the relay, will this cause any issues or problems. Is there anything i should be looking out for or something else i should do ?



Here is a basic diagram of the image, the point im interested in is in the red circle. Basically Blue/White wire going to the amp and being split either part way/at the harness connection/wherever to feed the relay.

Also with the 2012 model of pioneer decks does this method still work for bypassing handbrake ?

Cheers guys, thanks for your time and help

[sc400]

so are you trying to bypass the handbrake screen blanking (illegal)or set it up via a switch?

[Thirteen13]

Yeah i realise its not legal, and yes im wanting to bypass the handbrake all together, i know some people suggest a switch, but i doubt ill ever watch a movie while im driving anyway (keep that for home theatre!) and id rather just have some of the disabled features straight out.

My query is with the amp wire, and running a seperate external amp, say at the pioneer harness point solder, in the relay and the amplifiers wire together, will this cause problems or is there a better way of doing it?

Also with this model being so new, is it like previous model pioneer's where it only needs to relay, or are they getting tricker with this ?

[Daddio]

Out of interest, why use a relay for the handbrake safety?? Usually just earth the hand brake sensor wire (this means you can play DVD's on the move) The amp trigger wire is a low current 12v signal that turns on the amp, just wire it to the 'remote' input on the amp.

[Thirteen13]

Out of interest, why use a relay for the handbrake safety?? Usually just earth the hand brake sensor wire (this means you can play DVD's on the move) The amp trigger wire is a low current 12v signal that turns on the amp, just wire it to the 'remote' input on the amp.

Ive been researching google like mad to look for answers. In the US this deck is called the AVH-P4400, there is also the P8400/P8450 which is the next model up but shares basically all same parts as this deck.
I have read people suggest Earth out the wire, but apprently they are getting a little more saavy with trying to prevent people bypassing this feature and are suggesting that the last model and this model deck you cant just earth out the wire, apprently it needs active signal, hence why the relay will create the circuit.

Then again thinkkng about it, i recall this handbrake wire needs only go onto the earth side of the handbrake connection, so when circuit is made and the earth is connected it activates...
Like i said im a noob and i havent tested or tried anything yet and i guess the best thing to do would be exactly that.

Within that general area, what is the best place to source the Earth ? Should i go onto the harness black wire? Or perhaps somewhere else ?

Cheers

[Daddio]

The handbrake switch simply earths when you put the hand brake on...hence connecting to earth should suffice. Use any bolt near the head unit for an earth, or the earth on the loom.

[sc400]

if you use a non oem earth (bolt etc) bare the metal first to make good contact

[nuk1ear]

yeh just earth the "handbrake" wire. As long as it gets some contact its fine, you dont need to worry too much about scraping paint etc because its such a low current circuit which simply needs to be earthed. You should be fine with any bolt around the head unit area, but always best to test with a multimeter

Use the blue REMOTE wire to supply 12v signal to the amp to switch it on.

[Thirteen13]

Alright cool, logically it makes sense thats how it should work. Im unsure why people goto so much effort and put in relays.

However the earth solution ill give it a go and report back.

[Thirteen13]

Re-reading the manual it suggests the green wire needs to be connected to the power supply side of the handbrakes.

Just some further reading into needing a relay, it seems with newer HU's to get around just simply earthing out the green wire, the handbrake safety needs to have no power going to it before it starts up, once the car is running, when it receives the power signal/earth signal (as in from putting the handbrake on) then it says ok DVD ON. Because the Blue/White amp wire only sends power after the deck is started up, thats why this method running off a relay would immitate NO power on start up, AMP Wire gets power, engages relay then adds power to green wire.

This would suggest that either a manual switch or a relay be used to close and open the earth signal.

What about using a transistor ?

Would drawing some of the power from the amp wire into the relay cause problems to power up the amp ?

[Flex]

It all depends on the current drawn by the relay. The manuals states that the amp wire (blue/white) can source up to 300mA @ 12V. A standard relay (eg Bosch 0 332 019 150 ) has a coil resistance of around 85 ohm, which would draw about a 163mA @ 13.8V. Given most amps only need around 20mA to switch them on you should be OK. However make sure you put a diode (1N4007) across the relays coil terminals to suppress the back EMF the relay will create when it switches off as this could cause damage to the head unit/ amp.

[Thirteen13]

Cheers Flex thats super helpful mate

[Thirteen13]

Hey guys,

just needed some extra advice on this. I want to rig up the Quenching diode to this rig also.

Would the wiring be:

Black: 86 + 87
Blue: 85
Green: 30

With the Diode set between 86(anode) and 85 (cathode) ?

[Thirteen13]

anyone ? Still looking for some help if possible

[Flex]

Diode across 85 and 86 is correct, however you must put the negative on 86 and positive on 85 (Diode must be wired backwards).

So pin out will be:
85: Diode cathode, Amp blue/white
86: Diode anode, Ground
87: Green handbrake wire
87a: Not connected
30: Ground

Sorry I haven't replied to your last PM.