It sounds like AC ripple is getting into the DC power system.
How old is the battery? I'm just wondering if it's going high resistance, which wouldn't smooth the DC lines so effectively as a low resistance battery.
Just for reference, connecting my phone to the AUX socket and the power outlet in the car doesn't cause any kind of noise at all, so something isn't correct with your vehicle. Hyundai Ioniq 5 Ultimate. The family car.
2009 Rimini Red SE TD4. Gone.
2006 Tonga Green i6 HSE. Gone.
Audi A5 convertible, my daily driver.
1972 Hillman Avenger GT, the project.

Battery was replaced last year with an appropriate AGM one. So hopefully not that.

Yeah I can only assume I have something going on - although I’m scared to dig too far as this fairly cheap upgrade could end up costing a fortune! FL2 TD4 GS 60 reg Facelift - so many issues
2019 DS. Terribly unreliable.
Sold DS for a 2021 Mitsubishi Outlander PHEV. Fingers crossed....
Sold Outlander for a 2014 SD4 SE Tech because I’m mental
Now greatly regret selling the Outlander. MPG of the FL2 is atrocious and so are the fuel bills. Fun though 😎
Couldn’t afford the fuel bills so back to an older Mitsubishi Outlander PHEV. Significantly better than I remembered it to be…

Meant to say that when I was testing it again the other day I noticed there was a constant level noise with just the ignition on - engine wasn’t running. Once engine running, the noise was related to revs. FL2 TD4 GS 60 reg Facelift - so many issues
2019 DS. Terribly unreliable.
Sold DS for a 2021 Mitsubishi Outlander PHEV. Fingers crossed....
Sold Outlander for a 2014 SD4 SE Tech because I’m mental
Now greatly regret selling the Outlander. MPG of the FL2 is atrocious and so are the fuel bills. Fun though 😎
Couldn’t afford the fuel bills so back to an older Mitsubishi Outlander PHEV. Significantly better than I remembered it to be…

I have been looking around the internet and the audio noise problem seems quite common and every answer(s) seems to go along the same lines as we have.

Example
https://www.reddit.com/r/CarAV/comments/4h...ess_noise/

This was one of my Google searches
https://www.google.co.uk/search?q=noise+on...nt=gws-wiz

To go further you really need to 'see' the voltage output at various points of the supply route and insert the required inductive/capacitive load into the line as necessary. (Needs an Oscilloscope Type Device)
Basic Voltage Filters have an Inductive Load in line on the Positive lead followed by a Capacitive Load between Positive and Earth. They just smooth out the 'lumps' in the voltage supply.

As for your noise when the Ignition is on and the Engine is off, it possible that something else is running in the car. My FL2 seems to have a mind of its own as it powers up or down.

Do you have a stand-alone Battery Booster that could supply a separate12v Power to confirm problem is car 12v supply problem? FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 77k+ miles) (MY2015)
Metro in its 11th Year of (Extended) LR Warranty / Full LR Service History
(Expensive, but Trouble/Worry free - hopefully?)

Thanks again Ian. Yeah from all the searching I have done it also gives pretty much the same info - filters, grounding, accept the issue and move on.

I’ve just ordered one of those power filters so let’s see what happens.

And to answer your question about something else being on, I can’t believe I haven’t checked this but I have a dashcam as well, hard wired into the glovebox fuse box which comes on when the ignition is on/doors unlocked etc. I will try unplugging that

Thanks again FL2 TD4 GS 60 reg Facelift - so many issues
2019 DS. Terribly unreliable.
Sold DS for a 2021 Mitsubishi Outlander PHEV. Fingers crossed....
Sold Outlander for a 2014 SD4 SE Tech because I’m mental
Now greatly regret selling the Outlander. MPG of the FL2 is atrocious and so are the fuel bills. Fun though 😎
Couldn’t afford the fuel bills so back to an older Mitsubishi Outlander PHEV. Significantly better than I remembered it to be…

Ok, so a further update.

1. Unplugging the dashcam from the fuse box didn’t help.
2. Using a power supply from the mains, if I power the CarPlay unit, I still get the ground loop noise. If I run a different audio device off the same mains power supply, I do not get the noise.
3. However, if I plug the same audio device into power coming from the car, I get the noise.

So I have no idea why 1 device can have no noise from the mains but noise from the car power, and the CarPlay device has noise regardless.

You know when you wish you had just stuck to Bluetooth…. FL2 TD4 GS 60 reg Facelift - so many issues
2019 DS. Terribly unreliable.
Sold DS for a 2021 Mitsubishi Outlander PHEV. Fingers crossed....
Sold Outlander for a 2014 SD4 SE Tech because I’m mental
Now greatly regret selling the Outlander. MPG of the FL2 is atrocious and so are the fuel bills. Fun though 😎
Couldn’t afford the fuel bills so back to an older Mitsubishi Outlander PHEV. Significantly better than I remembered it to be…

I suspect that your results is due to how well the different internal power supplies of your units deal with smoothing out the AC Ripple on the FL2 Supplied 12v and/or House Supplied Power.
The noise will be at completely different frequencies, and it seems that the CarPlay unit does not cope all that well, so the chances are overcoming the problem do not seem good.

Of course your car may have excess ripple, but that needs special equipment to see (measure) whats happening.

When running your car will run far above the nominal 12v, so relies on the diodes and regulator circuitry to filter out the Alternator noise. FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 77k+ miles) (MY2015)
Metro in its 11th Year of (Extended) LR Warranty / Full LR Service History
(Expensive, but Trouble/Worry free - hopefully?)

Last edited by IanMetro on 15th Jul 2024 12:40 pm. Edited 1 time in total

Yup, that’s where my head is going - I could waste a huge amount of time and get nowhere. I may have to accept the trade off of the slightly dulled sound when using the isolator. The CarPlay unit was a gift so I don’t want to disappoint the gifted. FL2 TD4 GS 60 reg Facelift - so many issues
2019 DS. Terribly unreliable.
Sold DS for a 2021 Mitsubishi Outlander PHEV. Fingers crossed....
Sold Outlander for a 2014 SD4 SE Tech because I’m mental
Now greatly regret selling the Outlander. MPG of the FL2 is atrocious and so are the fuel bills. Fun though 😎
Couldn’t afford the fuel bills so back to an older Mitsubishi Outlander PHEV. Significantly better than I remembered it to be…

So a wee update. I have noticed that on the odd occasion that I want to listen to the radio, the DAB signal is terrible when the CarPlay unit is on. Was beginning to think the unit is the main cause of my issues.

Went out in the car today with my wife, who gifted me the unit, and needed GPS. Neither of our phones could work out where we were - like there was a terrible GPS signal. Turned off the CarPlay unit and the signal came back instantly. So, safe to say the unit is emitting some sort of terrible interference. Tried it with a different power supply and was even worse.

So it’s going back.

Not to say there isn’t still some form of ground loop issue but I’m not gonna figure it out.

Thanks for all the help. FL2 TD4 GS 60 reg Facelift - so many issues
2019 DS. Terribly unreliable.
Sold DS for a 2021 Mitsubishi Outlander PHEV. Fingers crossed....
Sold Outlander for a 2014 SD4 SE Tech because I’m mental
Now greatly regret selling the Outlander. MPG of the FL2 is atrocious and so are the fuel bills. Fun though 😎
Couldn’t afford the fuel bills so back to an older Mitsubishi Outlander PHEV. Significantly better than I remembered it to be…

Thanks for update.

A tale similar to the Wheel Tapper's Hammer.

For those to young to remember, in the days of steam trains (and lots of railway staff), when you pulled into a station a man used go down the train tapping the carriage wheels, whilst listening for a crack.
Legend had it that one such man 'condemned' carriage after carriage until it was discovered his hammer had a crack in it.

This CarPlay unit seems to fit this story.

I learnt my lesson quite soon after training as an Aviation Electronics Technician.
I decided to use the One Valve Amplifier that I had built from scratch during my RAF Apprenticeship to make a Record Player.
I bought some additional bits and a record 'Halfway to Paradise' by Billy Fury and proceeded to construct the Player.
However the resultant distortion was terrible, and being a keen new technician,I tried changing this and that, including several redesigns of the circuit. I did not succeed in getting it to work without the distortion, and the bits and the record found their way into a box and into the attic.
When, years later I came across this box, I played this record on my then modern HI-FI system, it sounded horrible and VERY distorted.

The lesson I learnt from this was do not be afraid to look carefully at the last changed item, even if it is 'new' or seems, at first glance, irrelevant to the observed problem. FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 77k+ miles) (MY2015)
Metro in its 11th Year of (Extended) LR Warranty / Full LR Service History
(Expensive, but Trouble/Worry free - hopefully?)

Love that!

Until I noticed the GPS issue I was trying to give it the benefit of the doubt, but that was just too obvious.

Ah well. Was an educational endeavour at worst. FL2 TD4 GS 60 reg Facelift - so many issues
2019 DS. Terribly unreliable.
Sold DS for a 2021 Mitsubishi Outlander PHEV. Fingers crossed....
Sold Outlander for a 2014 SD4 SE Tech because I’m mental
Now greatly regret selling the Outlander. MPG of the FL2 is atrocious and so are the fuel bills. Fun though 😎
Couldn’t afford the fuel bills so back to an older Mitsubishi Outlander PHEV. Significantly better than I remembered it to be…