Anyone handy with hi-fi / wiring? New head unit woes

[FieldAtlanta]

Hi all, one for the hi-fi whizzes here… I’m currently in the process of switching from an old double-din Pioneer head unit to a new Sony model in my Cayman 987.1 (non-Bose). I was hoping just to be able to plug in the old wiring harness to the back of the Sony unit and everything work, but unfortunately the existing plug doesn’t quite fit the Sony.

So, I attached the new wiring harness that came with the Sony to the ‘block’ (sorry, my technical knowledge isn’t the best!) which all seemed to go smoothly, re-hooked up the battery terminals hoping to see the head unit power on with ignition turn, but no sign of life unfortunately.

From these photos and description, can anyone help with what might be missing? I get the feeling that the red wire (which seems to go straight out of the back of the dash?) is important and is currently wired into the old pioneer harness - any idea how to connect to this?

Thanks in advance!

[RazerSauber]

I don't know what your level of knowledge is so I'll start basic. On your Sony harness, you'll notice you have a slightly thicker red and yellow wire with bullet connectors and a rubber sleeve in the middle. Both of those are 12v power. One is "ignition live" (usually the yellow and turns on with your key) and the other is "permanent live" (usually the red and is live, well, permanently). Sometimes these are the other way around so manufacturers let you change them easily with those bullet connectors. Usually, if they're the wrong way round, your radio would work fine while you're driving but then forget everything every time you turned it off (time, demo mode, input, audio settings, the lot). If either of those live wires isn't working, your radio won't work. You can test with a multimeter for 12v easily enough.

That Pioneer harness appears to have an extra red cable on it going somewhere behind your dashboard which would indicate to me that they've known something is wrong with one of the live wires and ran an alternative. First thing to try would be connecting that extra lead to the red wire on your Sony stereo and see what's what. It looks to have the same connector on it, give that a go.

[FieldAtlanta]

Thank you! I think you’ve successfully aimed this at my (very basic) level of electrical knowledge…

I’ve tried to take your advice and find a way to connect the red wire (which is wired into the fuse box) to the new Sony stereo but having no luck with exactly how to go about that.

This is the red wire which is wired into a fuse on the fuse box:


The ends of the wire:


The wiring hardness of the new hi-fi:


Do I need any specific connectors or am I simply being dim?

Thanks!

[defblade]

I think we're suggesting the following:



The "wrap this in tape" is probably next to the wrong connector... looking again, that's the one that you'll take out on 3 inches of wire. Wrap the other one!
Then do the same with the plug on the new harness, and you should have a male end to plug into the female coming out of the dash




However: be careful, that wire may be live if you've not disconnected the battery (and if you did disconnect it, did you re-connect before testing?? )

Where were the 2 ends on that red wire? If both were in the multi-plugs, that may actually just have been a tap to take off to something else (or did you say it came from the fuse box? If so, ignore me.)

You may instead need to do the same with the yellow wire - as mentioned, manufacturers are not consistent with the red/yellow, hence the bullet connectors.


A simple digital multimeter is cheap and can make very quick work of these sorts of problems!

[FieldAtlanta]

defblade said:

I
However: be careful, that wire may be live if you've not disconnected the battery (and if you did disconnect it, did you re-connect before testing?? !

Well, that escalated…


So frustrating - I’d listened to your advice and always worked on the wiring with the battery disconnected… until I didn’t! Having driven to Halfords to pick up a couple of extra bullet connectors, I just whipped out the stereo to double check what I needed and “zap!” - that ‘unknown’ red wire caught another wire and the car would no longer start. Even more frustrating was the RAC chap only having to change 2 fuses… electrics clearly isn’t my forte!

However - in a bit of a breakthrough I did manage to get power to the headunit today and it all worked fine. Joining the red and yellow wires from the Sony harness into each other (and disconnecting the ‘stray’ red entirely) as below in the bottom diagram for cars without ACC is what got it to work:


BUT there’s a problem - it doesn’t switch off! So - with the help of a multimeter (and a short circuit) I think I’ve realised that the ‘stray’ red power wire is something that’s been added by the previous owner and is definitely a power source. I’m still just at a total loss as to how to get it connected up though! Having connected as per the recommendation above, I get no power.

So this is where I am at. The below works, but doesn't turn off. Any thoughts?

[BlueMR2]

The red should be a permanent live, the yellow switched, so when you turn it on and off it tells the radio what to do.

If you give both inputs a permanent live, then it will always be on until you turn it off with the power button, same to turn it on as the stereo no longer knows when the car is being powered on.

[BlueMR2]

After disconnecting the battery....

As mentioned above, try that, remove both wires from that block, then put the one with the bullet connector back in making sure that both ends are connecting clean wire and well screwed together.

It seems that someone has messed with your wiring in the past. Also check the fuse for the red wire in the fuse box, it may have blown when you zapped the car with it and the RAC guy may not have changed it hence no power.

If it then works but forgets settings, then switch over the yellow and red bullet connectors.

[BlueMR2]

It seems like the Yellow is the permanent feed in your loom, hence it works and is always powered on.

If you can, do as said, remove the 2 leads with bare metal and just connect the bullet point connector, then check with the multi meter if the red lead gets voltage when you turn the key to acc, the one before starting the engine.

If so it's the switched live and should probably be connected to yellow and switch the yellow to red in the harness, however it would be unlikely to have a switched feed from the fusebox.

You may be better off just turning it on and off yourself, lol.

Edited by BlueMR2 on Saturday 15th October 20:56

[Polly Grigora]

If you were to say bks to it all and connect a permanent supply to the red and yellow at the head unit there is every chance that there will be a permanent current drain on the battery even when the unit is switched off

As already commented by others, permanent battery +ive and Acc +ive are needed, red and yellow are the cables to be connected to but although one would expect the head unit red to be permanent +ive and head unit yellow to be Acc +ive it's often found that they're opposite to what's expected

[BlueMR2]

It seems that when new your car used the fibre optic ( the 2 orange cable I believe) to control the HU and it's power, hence the red cable from the fusebox to run an after market hu as they don't use the fibre to connect (no idea how it works).

No idea what else is there, it seems there is a £200 box you can get to link everything together for some models. Its hard to tell where the wires from your unit connect to, as it seems alot of the usual suspects are handled by the fibre in your car as standard.

Possibly the previous owner has installed something extra ?

[FieldAtlanta]

Wow, hugely appreciate all the comprehensive replies - incredibly kind and helpful. I’ve followed the instructions and got to this point:


So that’s the fused red power wire cut from the small splitter box, wire exposed and crimped a female end of a bullet connector connected. I’ve then connected this to the red Sony harness bullet connector and it powers on, however still doesn’t turn off! Any other suggestions? I might try and connect the red fused wire to the yellow feed next - is that worth a shot?

[BlueMR2]

I think you may need to find a switched live to get it to turn on and off, you can try swapping the red and yellow, however i feel they are doing the same thing at the moment.

You may need to find a fuse in the fusebox that only comes on when you turn the key in the ignition.

I will post some links I was looking at when I’m on the computer rather than the phone.

I think you are mainly there but just need a switched live as it seems you have 2 permanent ones.

If you measure the red cable with a multi meter, does it have voltage all the time?

[BlueMR2]

The other thing I don’t quite understand is the large amount of colour wires at the back of the stereo cut out, do you have another kind of adapter back there?

[BlueMR2]

This thread may help you abit, https://rennlist.com/forums/987-forum/1200822-987-... .

Most specifically this post

"I had this confusion about the wiring from the original unit. The 12v to the fuse box for me is purely for switched power, whilst the red wire from the harness is constant. For some reason there isn’t another switched power that I could find going to the back of the PCM (though there absolutely should be, and that yellow wire seems to do nothing)."

"Switched 12 volt power lead can be obtained from the fuse box via the #9 position fuse on the 2nd row. It’s a 7.5 amp fuse for the telephone and power is cut as soon as the key comes out of the dash. Remove the fuse box cover and loosen the 3 screws that hold in the fuse box surround and you'll have plenty of room to get a connection into the fuse box. I used a very thin 22 gauge power wire and that allowed me to run the wire through some very small openings on the side of the fuse box and then back behind the carpeted panel that surrounds the fuse box."

"It depends on how the "keyed" power was done by your installer. When I did mine I used a fuse tap on on position C6. It unfortunately, does exactly as you described. It only powers in run mode and not in accessory mode when you insert the key.

So after doing some research, I found that the fuse at position B9 (used for telephone accessories) will activate/deactivate when inserting or removing the key. I moved my fuse tap to this location and it works!"






You need to check which slot the red wire is in in the fuse box, as it sounds like it needs to be in B9, then it should just be a matter of getting the red and yellow the correct way round.

[FieldAtlanta]

I believe that the red wire is exactly that - a switched live. It has a fuse on the fuse box that corresponds to “pccm” so the original stereo.

I’ve just checked with the multimeter and the red wire has power only when ignition switched on. The yellow is constantly powered:


Have tried to switch around the fused red wire to the yellow on the bullet connector (image below) but no power at all in that setup:

[Jazoli]

Can I suggest you take it to an auto electrician or audio installer, it will only cost an hour or two of labour to sort, it's quite easy if you know how, but you don't and are going round in circles

[FieldAtlanta]

BlueMR2 said:

You need to check which slot the red wire is in in the fuse box, as it sounds like it needs to be in B9, then it should just be a matter of getting the red and yellow the correct way round.

I think - without getting (even more) dangerously out of my depth I’m going to struggle to physically follow this cable to the exact fuse. My understanding is that the fuse added to D9 is the one linked to the red wire - this is also the fuse that tripped when I shorted the circuit yesterday.

[BlueMR2]

FieldAtlanta said:

Have tried to switch around the fused red wire to the yellow on the bullet connector (image below) but no power at all in that setup:

The red near your finger should be connected to the yellow that is unplugged as that is the permanent live the other end of that red wire is not connected to anything, hence will not be providing power.

[BlueMR2]

What is the model number of the new Sony stereo?

[FieldAtlanta]

Jazoli said:

Can I suggest you take it to an auto electrician or audio installer, it will only cost an hour or two of labour to sort, it's quite easy if you know how, but you don't and are going round in circles

A very sensible suggestion and probably the exact nudge I needed… a classic case of not knowing when to call it quits on a DIY project but you’re absolutely right. I’ll go and - coyly - see if there’s an auto electrician locally who can take a look.

Thanks all for your help - really do appreciate the time.