Aftermarket stereo with alternator whine

Question

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:

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?

Answer 1

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.

Answer 2

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.

Answer 3

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.