Having issues with radio/GPS/Sirius. The screen is flickering on and off. on 2009 Kia Optima

Not allowing radio, GPS, or Sirius to be used. I was able to plug in my Iphone and listen through speakers, but that was it. Brought it to shop and was told not under warranty any more. (3 months past) Have seen on other sites this same issue. Was wondering if anyone else had problems. Thanks

Asked by for the 2009 Kia Optima
I have seen some problem when charging system voltage was erratic due to failing alternator, or when getting too much A/C (ripple) from failing alternator diode and even with a failing battery or poor corroded ground connections that can effect any radio.
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First, this is my 2nd KIA Optima. I have a 2009. I have a Sirius, GPS, Ipod, and MP3 capable radio. The first one failed 4 1/2 months from purchase which was replaced under warranty. The second one just failed. The dealer manager and service manager have changed since my purchase and needless to say the service level has gone to the bottom. It appears that as they have become a popular car now, they no longer deliver the great service they did in the past.For that reason I have stopped having my Kia serviced at Kia shops and this will be the LAST Kia I buy.
I have to purchase the replacement from a KIA dealership. I've checked on the cost of replacement radio and can't wait to see what the dealership wants to gouge me for a replacement.