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Old 12-13-2014, 08:00 AM   #1
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Aux Start Switch

Recently purchased a Legacy 340KP. Over the years we have owned several motor homes and am familiar with the purpose of a switch to 'tie' all batteries together to give greater power to start the engine. On the Legacy I've observed that the Aux Start switch on the center console will blink/flash at times. Again it seems that at times the flash rate is faster than at other times and when I checked yesterday, it wasn't flashing at all. So, my questions are: is there some monitoring/warning function built into the Aux Start circuit and if so, what are they?

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Old 12-17-2014, 06:08 PM   #2
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Okay - I think I have the answer.

The Legacy uses a product called a Battery Isolation Manager [BIM] that is manufactured by Precision Circuits Inc. The BIM performs a multitude of tasks including tying the coach and chassis battery together when the Aux Start switch on the console is pushed and held on - the normal function for all such switches I have encountered on previous coaches. It turns out that the BIM also monitors both sets of batteries - coach and chassis - and manages charging both of them from various charging sources - engine generator, battery charger/inverter, etc. So what I am observing - the Aux Start switch glowing dimly and flashing brighter about every 30 seconds is an indication of the voltage being applied by the BIM to the relay that ties the two battery banks together.

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Old 12-17-2014, 06:34 PM   #3
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Location: Dallas TX
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The way it was explained to me is like this. When plugged into shore power, and the house batteries get charged then it starts to charge the chassis battery. The light flashes to indicate the chassis battery is being charged. I think you are basically saying the same thing.
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