Howdy folks, my NEX4200’s Bluetooth has grown increasingly noisy over the last few weeks after nearly 2 years of using Bluethooth for the majority of listening.

Even when all pairings have been deleted when Bluethooth is selected as a source the white noise pushed to the amplifiers is deafening.

This occurs, even when in the middle of the country (away from most signal sources), with no other electronics in the car, and with the car turned off (battery only) – with all accessories disabled.

This even occurs when turning off the amps and hooking up speakers directly to the head unit.

It occurs with different devices when paired and when nothing is paired– and is immediate when the key turns on power.

Once the pairing syncs and music begins the horridly loud noise continues. 

Selecting any source other than Bluethooth and the headunit functions as expected.

Does anyone know of an aftermarket Bluethooth module that is compatible with this unit or of a way to fix this most irksome issue?

Best

I found the culprit - the initial voltage available to the car UPON startup impacts the level of BT noise of this headunit for the entire time the car is on. 

My battery (Duramax Gold) is 3 years old and only retains 12.09v.

Swapping to a new battery which retains 12.65v and the bluetooth noise is immediately gone

Swapping to the 3 year old battery and it immediately returns 

Refreshed the 3 year old battery - it now retains 12.59v and the bluethooth noise is immediately gone

How i refreshed the battery: 

• removed plastic cell covers
• slowly poured baking soda into each cell to neutralize the acid, left overnight, poured out
• mixed 1 part epsom salt to 3 parts distilled water
• poured into cells to correct height, capped, shook
• took to mechanic and had them toss it on a 3phase charger overnight ($10)