[Fulltiming]

The engine (chassis) batteries don't have to be completely dead to not start the coach. Any time it is cold or the batteries don't have a good charge on them, merging the batteries can add extra power to get you started. With the switch in the center position, the house (or auxiliary) batteries are isolated from the engine (chassis) batteries. The generator is typically wired to start from the house batteries. If your engine batteries are low, place the merge switch in either the up or the down position and see if that allows you to start the engine. If one set of batteries is REALLY low, the merge solenoid, as Dean pointed out, may not engage. If this is the case, flip the merge switch to the opposite merge position and it should tie the two systems together. Under most circumstances, there is enough juice in either set of batteries to engage the merge solenoid so it will not matter whether you flip the switch to the up position or the down position. Newell was just eliminating another potential reason for you getting stranded.