POWER PROBLEM WITH NEWMAR, NEWBIE

There is a relay in most coaches that allows the house batteries to be charged by the alternator. It sounds like to me that that relay isn't closing when you are running the engine. This would cause the batteries to completely drain fairly quickly. Once lead acid batteries have been completely discharged they are damaged and while may come back up they would have greatly shortened life and be unable to hold a charge as long. Depending on how your battery bank is wired Series or parallel any single low or weak battery will bring down the entire bank. This is more of a problem for series wired batteries than parallel but this can still happen with parallel because more of the load is carried by the stronger battery. To test this theory with the vehicle running check the voltage at the house battery bank terminals. Check the voltage at the chassis battery and note it. Next check the voltage at the House battery bank it should be very close with only a few tenths of a volt drop. If it isn't then the relay isn't closing for some reason. A final test requires another person. With the engine running check the voltage at the chassis battery. Have another person press and hold the "emergency start" or "battery boost" button in the driver's area. Check the voltage at the House battery bank. It should be similar to the chassis battery bank. Keep in mind that this relay can be damaged by attempting to charge completely dead house batteries with the engine running. Typically they can't handle inverter loads for long and will either quit working or shut off for self protection.