Start/Stop + Aftermarket head unit = Hair Loss

[moodi]

Your head unit should use two 12v lives, one permanent and one 'switched' normally with the ignition.

The company fitting it should be able to find a suitable source for each, ideally within the original HU loom. Failing this and regardless of your stop/start functionality there will still be 12v supplied to other parts of the car permanently and also switched. The switched will always supply 12v as long as the ignition is on, regardless of the engine being on off or stop starting etc. My original option 2) allows you to tap into those supplies via existing fuse circuits.

Think of it like this. Even your car stop/starts, your heaters and fan still work, your headlights stay on, your interior LEDs are still lit and your window wipers don't stop mid wipe. Those are all things that get their supply from the main battery, normally on with ignition and not affected by the engine cranking over.

If your garage really have run a direct line to the main battery this should make whatever it is connecting to always on, regardless of if the engine is cranking or not. If you do not believe me wire up a 12V LED to your main battery (with some thick wire) and watch it stay on even when your engine stop, starts etc. Again, this depends on what exactly they wired to the battery directly. The perm supply, the switched supply or both. "both" would make everything work all of the time even when your key is not in the ignition, not ideal but it will tell you if your HU has any issues in itself (not saving settings etc) which is a possibility of course. If the HU is faulty it could be working fine in all other aspects but not storing settings or doing things it's memory should, even with the correct 12v supplies.

My advice would be to get a professional second opinion and go elsewhere, if you can.

 

[Wuffles]

Whilst I appreciate the long reply, unfortunately most of the points you raised have already (I think) been dealt with in the many other replies.

It’s not a simple case of a permanent live, or an issue with the head unit. It’s the fact that the permanent live in the original head unit wiring loom goes to sleep, so to prevent the head unit losing settings overnight they ran a wire from the battery not understanding that there’s a complex set of electronics feeding from an auxiliary battery during stop/start - this is how I understand it currently anyway. Not that I should be the one trying to understand this.

 

[moodi]

Got it, but wiring straight to the main battery should give you 12v - nothing to do with the 'complex' electronics you mention.

Have I misunderstood?

 

[Wuffles]

Got it, but wiring straight to the main battery should give you 12v - nothing to do with the 'complex' electronics you mention.

Have I misunderstood?

The engine crank drops the voltage and makes the head unit restart, didn’t do that when wired into the loom. The electronics I’ve been made aware of in this previous answers are to avoid that happening by switching to aux battery during stop/start, this masking the voltage drop.

I’m limited as to who I can use down here in the south west. There’s only a couple of places available to me, and one of them is the outfit dealing with it already.

I suspect I’ll have to call them when they reopen after the Christmas break, make them aware of the aux battery and get them to go and do their home work before allowing me to do another 50 mile round trip for nought.

 

[Wuffles]

From your description, it seems that a permanent live have been taken directly from the battery, is this correct? If so, the installer has by-passed the complex circuitry involving the Aux Battery/Voltage Converter (in later models) provided by MB to combat the voltage drop during the ECO re-Start. A relay is used to switch to the Aux Battery during the ECO restart to avoid the electronics from suffering from a voltage drop.

If your head unit worked perfectly fine with the timed live, then it would suggest that your main battery is not the problem? You can always get your main battery tested for free to eliminate this from your troubleshooting list?

This is where I’m getting my info by the way.

 

[moodi]

How much is the voltage dropping between cranks?

 

[moodi]

This is where I’m getting my info by the way.

And that is all valid and another reason we normally use switched circuits from the fuse box rather than tap to any battery directly

 

[Wuffles]

How much is the voltage dropping between cranks?

Not my pay grade

 

[moodi]

Ok, best of luck finding a solution and keep us updated

I'm sure there are lots of folks more knowledgable on here including those @ Comand.

 

[Wuffles]

I’ll certainly update this once it’s fixed. I’m into this outfit for £150 so far and won’t be paying any more. Three 50 mile round trips already and countless wasted hours.

Having some information to give them to go on certainly helps.

I really appreciate everyone’s input so far!

 

[m80]

How much is the voltage dropping between cranks?

For a healthy battery that would be less than a failing battery.
I've seen new batteries drop significantly. Then a componnet failing is dependant on its own threshold.

 

[Wuffles]

I'm back.

I rang Comand and spoke with someone there who suggested the garage had done exactly what they would have done, run a dedicated lead from the battery and use an adaptor as I had tried before. He was surprised it hadn't worked, we talked for a minute or two about things and then he suggested having the battery tested (as I kind of vaguely mentioned it could be that).

I had the battery tested and it showed as needing replacement, so meanwhile emailed Comand to ask which particular lead they would recommend to defeat the stop/start issue. Unfortunately the person I am dealing with now doesn't agree that there's a "timed live" and that running a wire to the battery directly wasn't something that should have been done.

I'm fairly close to giving up now, as you can imagine.

Anyway, just to update you all. New battery fitted today, head unit still reboots without any adaptors fitted. Sent the easy to fit adaptor back to the retailer so that's not an easy try now.

Oh, an interesting by-product of not having the standard head unit and having a battery changed is I now can't set the clock - assume I need to have the original head unit coded out of the vehicle so the time/date option appears on the settings menu on the dash.

 

[moodi]

Are you sure the head unit itself isn't faulty?

 

[Wuffles]

Are you sure the head unit itself isn't faulty?

I can't be 100%, but it was working fine in the last vehicle I took it from, and nobody has put up a decent argument that it's not doing exactly as it should. When it was connected to the loom it worked fine but reset overnight due to a "timed live" (people either believe this is a thing or don't) and now it's connected to its own fused permanent live to the battery, it's rebooting itself during stop/start, which is also correct - edit to say, correct in that it's missing the auxiliary battery wiring, so should reboot each time.

Possibly the loom's permanent live was affected by the fading battery and wouldn't normally have a timed live, or perhaps the normal "permanent live" found in the head unit wiring loom isn't the only one, and there's also a real permanent live in there somewhere that's protected from the stop/start by the auxiliary.

However, finding anyone who knows for sure on this is the tricky bit

 

[chrisk2010]

I'm going to be getting in over my head here at the beginning of this thread I was thinking it was the battery and I imagine the fitters you using have already done what is suggested in the below link pointing at some cars may need the yellow and red wires swapping around, the yellow wire is a "memory wire" and always needs a permanent live:

Sony Head Unit Resetting Itself

This seems to be a common problem no matter what car you have after a bit of googling but moving from one car to another seems to warrant switching these wires.

I few other things suggested could be a capacitor in the head unit not holding a charge and has become faulty or possibly just a bad ground. I presume a bad ground would cause the head unit to switch off though if you went over a bump or slammed the boot.

Personally I would find the memory wire for the headunit and make sure that is getting a permanent live sometimes starting again at the beginning is the best place to start when you've got in too deep especially with wiring.

 

[Wuffles]

I'm going to be getting in over my head here at the beginning of this thread I was thinking it was the battery and I imagine the fitters you using have already done what is suggested in the below link pointing at some cars may need the yellow and red wires swapping around, the yellow wire is a "memory wire" and always needs a permanent live:

Sony Head Unit Resetting Itself

This seems to be a common problem no matter what car you have after a bit of googling but moving from one car to another seems to warrant switching these wires.

I few other things suggested could be a capacitor in the head unit not holding a charge and has become faulty or possibly just a bad ground. I presume a bad ground would cause the head unit to switch off though if you went over a bump or slammed the boot.

Personally I would find the memory wire for the headunit and make sure that is getting a permanent live sometimes starting again at the beginning is the best place to start when you've got in too deep especially with wiring.

It’s not losing its settings in that way, and with a dedicated fused live from the battery (I saw it when the garage swapped the battery) it’s definitely got a permanent live.

I’m going to do the school run shortly. I will get in the car, turn it on and all settings will be correct. I then press the eco button to stop the radio rebooting the first time the car goes into stop/start. Other than that it’s fine. Annoying but fine.

 

[chrisk2010]

Ahh I see! Told you I was in over my head

I was just brushing up on the stereo wiring as I have only done it a few times and as long as the yellow wire is wired to the battery then it should be fine as the red wire is for the switched live and black is ground.

I thought maybe if they had inadvertently mixed the red and yellow up then it would cause the radio to reset every time the ignition is switched via stop start or over a few hours after the car is turned off and the capacitor in the head units charge fades.

Maybe it's worth having the head unit bench tested?, what model is the head unit?

Sorry I couldn't be of help I fella hope you find the solution.

 

[Wuffles]

Ahh I see! Told you I was in over my head

I was just brushing up on the stereo wiring as I have only done it a few times and as long as the yellow wire is wired to the battery then it should be fine as the red wire is for the switched live and black is ground.

I thought maybe if they had inadvertently mixed the red and yellow up then it would cause the radio to reset every time the ignition is switched via stop start or over a few hours after the car is turned off and the capacitor in the head units charge fades.

Maybe it's worth having the head unit bench tested?, what model is the head unit?

Sorry I couldn't be of help I fella hope you find the solution.

I'm bringing my incompetence to the table in my answer though, my understanding is that if the wires were muddled, you'd be resetting frequently (after each ignition off/on anyway), whereas that's not the case. Permanent live to the head unit is still the same way round whether from the original head unit loom or from the battery, so I'm excluding that from the possible issues as it produced different results.

I'm not sure what could be tested on the head unit, it's work exactly as expected.

Let's put it this way, if someone could categorically state there is no such thing as a timed live, I'd have a direction to point the installers (if that were the case, I wouldn't touch the original installers with a stick going forward as they are the ones who said that was the case).

If someone could categorically state that if using a live directly from the battery you absolutely need a start/stop voltage stabiliser then I'd know to pursue that.

Problem is, both scenarios are true/false depending on who you speak to, even from the same company (Comand) when I rang/emailed them and spoke to different people I got completely different answers, so it's kind of hard to know what is true.

I'll keep plugging away. I'll most likely ring Comand back today and try and speak to the guy who originally said the installers had done the right thing with a permanent live to the battery and that the use of a stabiliser is correct. I only wanted to know which one they use given it's been proven, I really wasn't expecting an entirely different answer from the next person I spoke with there.

 

[chrisk2010]

God I wish I could help I have read through the thread a bit slower than I did the first time in an effort to understand better.

I have no idea what a timed live is I googled it and it doesn't exist in the infinite knowledge of the internet so.... assuming the memory wire is fine as that now has a permanent live and you not losing your settings any more?! but the head unit still switches on and off with stop start and the ignition key BUT when it was connected to the cars original wiring loom protected from the stop/start by switching electronics to the Aux battery when need it worked fine then somehow the red switched live is drawing power from the wrong place.

Whether it is down to a battery voltage drop assuming both wires are wired direct to the battery or the red wire is drawing power before the protected circuit and like you've already said needs to go back to the cars original wiring.

Think I have talked myself around in a circle there

If I was doing this at home I would put it back to the original setup which isn't affect by the stop start but does lose it's settings then I'd find the memory wire ( yellow ) and run a permanent fused live to the battery. Then it should work through Start/Stop and retain it's settings.

Sorry if I'm not being helpful, I really do hope you get to the bottom of it.

 

[m80]

Do you still have the original HU.
If that runs no issue it points to the Sony being at fault.