Hi. Started up my new 850 (1993/169,000 miles), with settings on "Auto" (thought I read to do this in the manual, and have been running car this way w/o incident for first 1,000 miles). This time, blower started running hard. About 1/2 mile into it, all idiot lights came on, car started progressively losing power. Crawled at nearly zero speed to a safe stopping place. Turned off car. Waited. Turned on car. Blower started again. Moved slider to high, and illogically, blower stopped. Car ran fine. Since then, I've been following a suggestion to keep setting at "0" or "1". 400 miles later, car is still running fine w/o repeat of power loss incident. However, with winter coming, I will want the option of running the blower at higher speeds. Does anyone know what might have been going on? P.S. Battery is 3 years old. When's a good time to change out? What type is best? Thanks.