Accessory power is on when ignition is off - 9n3 Polo

[seangti]

Hi,
I'm putting in an aftermarket head unit in my 06 9n3 Polo GTI. I have identified all the power related wires, though interestingly the accessories wire provides 12v when the ignition is off, but around 4.5v when the ignition is on. As a result, the head unit will power on ONLY when the ignition is off, yet turns off when the ignition is turned on. i.e. it's back to front on accessory power.

This is quite strange as the cigarette lighter runs constant on this car, yet my other polo (a 2008 model) will only power the cigarette lighter when the ignition is on.

Anyone have any tips for me please??? I'm at a loss.

Thanks

[nat225]

may by try connecting the 12v constant power direct to the fuse box. and connect the accessory wire to the switch wire?

used to do some car audio install loooong time ago. including making up sub boxes (jigsaw, mdf board, carpet and stuffs).

[seangti]

Thanks Nat. What do you mean switch wire? Find another power line that triggers on accessory and butt into that??

I had tried pulling the head unit out of the other polo to check, though I'd paid to have that installed and must be bolted in as the Pioneer 'keys' to removed it didn't help.

[h100vw]

Thanks Nat. What do you mean switch wire? Find another power line that triggers on accessory and butt into that??

I had tried pulling the head unit out of the other polo to check, though I'd paid to have that installed and must be bolted in as the Pioneer 'keys' to removed it didn't help.

All the wires you need should be there behind the dash.

Did I share the wiring diagrams with you Sean?

https://www.dropbox.com/s/wh8v3bitup...polo2.pdf?dl=0

[seangti]

All the wires you need should be there behind the dash.

Did I share the wiring diagrams with you Sean?

https://www.dropbox.com/s/wh8v3bitup...polo2.pdf?dl=0

Thanks Gavin. Yeah all the wires are there, it's what the ignition/accessories does that has me confused. Powered when off, not powered when on. Will poke more wires with the multimeter.

[DV52]

Hi,
I'm putting in an aftermarket head unit in my 06 9n3 Polo GTI. I have identified all the power related wires, though interestingly the accessories wire provides 12v when the ignition is off, but around 4.5v when the ignition is on. As a result, the head unit will power on ONLY when the ignition is off, yet turns off when the ignition is turned on. i.e. it's back to front on accessory power.

This is quite strange as the cigarette lighter runs constant on this car, yet my other polo (a 2008 model) will only power the cigarette lighter when the ignition is on.

Anyone have any tips for me please??? I'm at a loss.

Thanks

Sean: Hi- I'm mighty intrigued by your observations!!! I can totally understand why the ciggy lighter has a permanent 12 Volt supply - it's because the ciggy lighter is hard wired directly to fuse 34 (SB fuse box) as per the picture below which is from my polo 6c, but your 9n is similar:



But (like you) I'm at a loss to understand your 4.5 Volt measurement! Where precisely did you put the leads from the multi-meter? Are you sure that you weren't measuring the voltage on an output wire from the BCM (J519)?

[seangti]

Thanks for your input. The cigarette lighter one is actually handy, as my other 9n3 polo is only on accessories which can be a PITA.

I put the multi meter into the factory wiring harness itself for the HU (the wiring block in the 7th pic- here). I haven't yet traced it back to the fuse box to see what's going on there.

The yellow wire is constant 12v
The red is the ignition which is playing silly buggers on me.
There's an orange which triggers off head lights with ~0.3v when head lights are on and zero when off.
The blue - remote is connected to an inline "somethingy" which runs into the radio jack so the reception is good. (e.g. 4th picture of this thread)
Black is obviously ground

It's this ignition one that has me stumped. The previous head unit is the one listed in the above mentioned thread, the ANS-420.

[DV52]

Thanks for your input. The cigarette lighter one is actually handy, as my other 9n3 polo is only on accessories which can be a PITA.

I put the multi meter into the factory wiring harness itself for the HU (the wiring block in the 7th pic- here). I haven't yet traced it back to the fuse box to see what's going on there.

The yellow wire is constant 12v
The red is the ignition which is playing silly buggers on me.
There's an orange which triggers off head lights with ~0.3v when head lights are on and zero when off.
The blue - remote is connected to an inline "somethingy" which runs into the radio jack so the reception is good. (e.g. 4th picture of this thread)
Black is obviously ground

It's this ignition one that has me stumped. The previous head unit is the one listed in the above mentioned thread, the ANS-420.

Sean: You have me totally confused - which is not hard to do!! Here's a section of the wiring diagram that h100vw provided showing the power connections for the factory radio (see section 4)



D is the ignition starter switch, S163 is fuse 2 in the battery fuse holder (it's a terminal 30 supply - so it's permanent 12Volts) and J503 is the factory radio. Notice that the wires are multi-coloured! There don't appear to any single colour wires in the factory loom. Hence my confusion
Don

[seangti]

Thanks Don, I had a quick look while out for lunch and also started checking the fuse box to trace it back. Of note, with the ignition off I was getting voltage in the 11's, where as constant was 12.3-12.5. So was trying to find another 11v reading from the fuse box.

I didn't find a fuse which replicated the voltage that I was getting off the harness.

You are right about the colour and what I was referring to, now that I better know what to look at. In saying that, I couldn't identify the wires as colour coded above.

Additionally, I noticed the voltage drop on accessory line also drop to around 4.5v when I turned the head lights on while the ignition was off. So the voltage drop is consistent when turning the lights on and off, as it is when turning the ignition on and off.

[DV52]

Sean: Don't know how to say this tactfully, but what you are describing isn't credible (sorry to be blunt). Don't take this the wrong way, but it simply isn't possible for the power supply bus on the accessory position to operate on 4.5 Volts! Nothing inside the car would work at this voltage (assuming that the battery is OK). Yes, a (very small) deviation from full battery volts is to be expected, but if the engine isn't running and the lights are in the off position - the volt-drop on the accessory bus should be minor - definitely not around 9.3 Volts (i.e. 13.8V-4.5V). What are you using to measure this voltage and where precisely are you putting the meter-leads?
Don