400fanboy

Hi guys

Driver door speaker died, sub died, no bluetooth or any AUX input. It was time. Got a full system. All 6 speakers replaced, 500w amp powering a 10'' sub, Kenwood head unit. Kept OEM nav\touchscreen.

I had a shop do it since I am not a wrench. They did a great job with the install. Seamless wires, beautiful matching job with the new mount for the head unit, everything put back as it was perfectly.

However... I've got some nasty alternator whine now. Directly tied to engine RPM's.

The shop claims that it is from the stock computer. Not the radio, that was removed, but the stock "computer", whatever that is. They say the new system and old system run in parallel. They had to move the stock computer and relocate it in order to keep the touchscreen because it controls the HVAC, NAV and other systems. This is causing interference on the audio which presents as alternator whine. They double checked the all of the grounds and wiring after I mentioned it and they say they've done everything they can but can't fix it. It is not some guy in his garage, it's a large shop with a great reputation. Not their first old Lexus they've worked on.

Are they correct about the stock computer interfering with the new system? Are they missing some unique factor with the LS? What are my options here. Thanks

AlaskanLS

This happened to me before when I installed aftermarket stereo in my Land Cruiser. In order to get rid of the whining you have to bypass factory amp. The reason it's making whining noise is because your aftermarket head unit has already built in Amp and on the top of that it's also using factory amp. If you want to keep the factory amp then you would need a device called PAC SNI-1. After installing that device the whining noise will go away but not completely. Some times you will hear a loud bang noise from the speakers for a split second when you shut off the car engine. Your best bet would be to get rid of the factory amp. I bought that device but I didn't like the sound quality. I ended removing the factory amp. You can bypass the factory amp without removing it from the car.

400fanboy

It does bypass the factory amp I believe. It is all controlled through the new Kenwood head unit, the stock radio is gone. There are two "amps", one power pack for the door speakers and then a 500w unit for the sub.

They said they've worked on removing it, including even putting a silencer (?) filter onto it to no avail.

AlaskanLS

In that case the noise is made by the power pack amp for the door speakers. Because the power to the door speakers are going through two amps i.e built in amp of head unit and the power pack amp that u mentioned. When u use two amps simultaneously for the door speakers u will get whine noise. Install that RCA filter that I have mentioned, the whine will go away.

400fanboy

I believe they already have a silencer\filter on the car. I don't know anything about it's specs. I will double check and get more information about it when I go back in a week or so.

One more symptom I noticed - the whine gets significantly quieter as the car warms up. After about 30 minutes, it's barely audible. But when it's cold it's very pronounced.

AlaskanLS

The whine you hear through speakers is from the alternator. When the engine is cold, the rpm of the engine is high to warm up the engine faster. Due to high rpm alternator generates little bit more electricity, once the engine is warmed up, the rpm drops and the out put of the alternator drops too. You need amp only for the sub-woofer, you shouldn't use amp for the door speakers because I told u previously that these head units comes with built in amp for the door speakers.
If you disconnect the stand alone amp for the door speakers, your problem will go away completely.
There could be one more reason for whining noise and that is the speaker wires not properly insulated and touching 12 volts or ground wires.
Make sure the shop has plugged in the radio antenna wire into the right socket. Some of the stereos has two out put sockets for radio antenna wire.
Car ECU (the computer your shop is talking about) has nothing to do with the whine.
Once again make sure your car's factory amp is disconnected.

400fanboy

You don't hear it while idling, so the cold start with a higher idle RPM doesn't matter. I mean you hear it more at 2-3k rpm when the engine is cold than when it's fully warmed up. But regardless, that sounds like semantics anyway.

Awesome, thanks for the info. Will report back once I have gone back. I have to go back anyway because my sub was out of stock, so they gave me a temporary one with the option to change to the (better) one.

iltolesjr

Is that the best method?