Alright; batteries will be my first check. PO told me he just replaced the aux batt, and also the alternator not long ago. He suggested the intermittent aux failure could just be a loose cable connection. I'm not sure if he was just blowing smoke or had an intelligent reason for that suggestion.

I've read other posts here suggesting that a good scanner would be a wise investment. So, if anyone has a recommendation of brand, I'm all ears.

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Paul
2004 E500 4matic; 72,000mi