I replaced the OEM stereo unit in my 2001 Toyota Celica with an aftermarket one to have bluetooth, USB connectivity, etc. No new wires were added, I just used the original wiring with an adaptor like this one:

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The new stereo has various inputs on the back for RCA, ANT, GPS, etc, but none of them are being used.

I'm getting what I believe is alternator whine in the stereo. It's usually not there when I start the car, but eventually shows up after 5-10 minutes of driving and then stays until I shut the car off. The whine pitch varies with RPM and is more audible and lower pitch when I'm idling at a red light. Shutting the engine off and having music play on battery power is perfectly clear.

I read that a bad ground is often the cause, so I took out the ground pin and wired it directly to the car frame under the dash, but this didn't seem to make any noticeable difference. Most other suggestions have to do with RCA cables and such, but I'm not using anything else. What are some other things I could try?

  • 1
    Congrats on your first post to Motor Vehicle Maintenance & Repair and welcome! The ground is the first place I'd have looked as well. Make sure the antenna is securely fastened as well. Other than that, I'm not an audiophile enough to give you a good answer, lol. May 24, 2018 at 17:18
  • There are suppressors that can be fitted to the alternator output terminal for one, or you can get a dc to dc converter which can isolate the supply to the stereo.
    – Solar Mike
    May 24, 2018 at 17:25
  • @Paulster2 Thanks! I'm not actually using the antenna at all, I never listen to radio and don't even have it screwed into the car outside. Should I plug the antenna cable into the stereo? It's currently unplugged and just coiled up under the dash.
    – Egor
    May 24, 2018 at 19:20
  • @SolarMike So for the dc converter, would I cut the +12V wire in the bundle going to the stereo and wire the converter into the cut?
    – Egor
    May 24, 2018 at 19:22
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    Something really quick, easy and cheap you could try is putting Ferrite Core on the ground line (and/or other lines). This other stack post explains what I'm talking about, and here on Amazon you can see exactly what I'm talking about and their costs. May 24, 2018 at 20:20

3 Answers 3


Clean battery posts. See if adding jumper cable from battery to alternator housing helps to check poor alt/engine ground. Do same for radio ground. Have alternator checked at parts store. Ferrite bead/ferrite core noise supressors to stereo ignition, power and ground wires.

  • I tried all sorts of grounding tricks, but nothing worked. Alternator and battery checked out fine. I ended up installing a noise filter on the power line, with a ferrite choke and a capacitor in it, and the noise is gone now.
    – Egor
    Jul 31, 2018 at 23:45

There are several ways to reduce alternator whine, but the only to remove it entirely would obviously be to find out what is causing the noise.

  1. Make sure to check that your head units data cables (wifi, GPS, USB, etc. ) are routed away from your speaker wires. These can cause interference and introduce a whining noise to your audio. Also consider running a heavy guage ground wire directly to the head unit, as opposed to grounding to the wire harness.

  2. Consider installing a grounding kit under the hood. This consists of attaching 4-8 guage cables to different parts of your car, such as from your negative battery terminal to your alternator, and multiple points of your cars frame. The quality kits tend not to be cheap but people swear by them and they defi5 improve the rest of your cars electrical conductivity.

  3. In the past I have used Ground Loop Isolators to filter out the whine from the audio. This is more of a band-aid than a fix. They typically have a left and right channel, and a ground wire. You simply attach your left and right head unit wires to the the input on the GLI, and then attach the output wires of the the GLI to your cars speakers. You then attach the ground wire to a ground point in the car. Ground loop isolators are pretty cheap and do the trick when all else fails.


Im having exactly the same issue with my Bluetooth - I can hear a noise that changes with the car RPM. I’m going to add a battery bank as a source of Bluetooth power and then just charge the battery bank from the car - hopefully that will filter out the noise.

Update: The battery bank solved the issue but it was annoying as I had to manually switch it on and off.

I’ve tried adding an audio filter (Ground Loop Noise Isolator Neoteck Auido Noise Filter Eliminator with 3.5mm Jack Audio Cable) which removes the noise but made the bass sound low quality and cheap (like the speakers couldn’t handle it).

I’ve installed a 12V power filter (10 amp audio noise filter suppressor - “bumper” brand) and that solved the issue.

  • Welcome to Motor Vehicle Maintenance & Repair! Unfortunately, this doesn't answer the question and would be better as a comment. If you implement this solution and it works, please come back and let us know!
    – Dan A.
    Oct 3, 2018 at 16:40
  • @DanA. - Actually, it does answer the question. Mike is suggest since this is the avenue he is going to take, for the OP to take the same route. Just a little different way of answering it. The OP is looking for different ways to solve the problem, and this could definitely be one of those ways. Oct 3, 2018 at 18:18

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