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mrk · 03-28-2017, 03:51 PM

Last November I fully charged my chassis batteries before placing the Tradewinds into storage. Less than a month after that, I went to check something and found the batteries were run down. I recharged them again and removed the positive connector to keep them from discharging Today, they both showed 12.20 volts, and they are still disconnected.
I did, however, plug the motorhome into a 120 volt outlet so that I could charge up the house batteries, which were reading 12.01 volts. I did not turn on the salesman's switch or the inverter. After about 90 minutes, the weather radio (part of my CB radio) suddenly came on with a weather warning. (It's supposed to do this, even when the CB is off, and it scares devil out of me when that happens!) I sat at the drivers seat and turned on the CB, which was functional. Hmmm, how does this happen? Isn't it on the chassis battery?
Out of curiosity, I flipped the switch to the dash radio. Nothing. I flipped the switch to the map lights, and they illuminated. Again, aren't they a part of the chassis battery system? (If not, the house batteries were still disconnected.)
While I sat there scratching my head, the entry stairs suddenly deployed. (The door was open, but I keep the steps in the 'travel' position when the chassis battery is disconnected.) They would not go back up when I closed the door.
I pushed the generator start switch. Nothing at all. I expected it to crank over, as I believe it is wired to the house batteries, or is it?
I also checked both cigarette lighters, to the left of the driver, and to the right of the passenger. Both were reading about 14.2 volts (same as the house batteries, which are being charged.)
I continued to play with the dash. I pulled the headlight switch, and everything went dark. Pushed it back in and detected a faint glow with the light in the CB radio, which seemed to get increasingly brighter. After a few minutes, I turned the map lights back on, and they came on fully bright.

There's more, but you get the picture. It seems that I've either got a short or some crossed wiring. Does anyone have any idea where to start? Might there be some feedback through the sensor wire to the alternator? Also, I believe that there is a circuit that keeps both batteries connected for charging until they drop below a certain voltage. Might that circuit be feeding the chassis circuits?

Any advice would be appreciated. DW is googling "Exorcists".

jim27358 · 03-29-2017, 06:49 AM

No sure about yours but anytime mine is connected to shore power it turns on anything that is connected to the house electric circuits. Mines a Newmar.
You can disconnect the negative terminal from the batteries and isolate them saves the chance of arching.

mrk · 03-30-2017, 08:11 AM

Quote:

Originally Posted by jim27358

No sure about yours but anytime mine is connected to shore power it turns on anything that is connected to the house electric circuits. Mines a Newmar.
You can disconnect the negative terminal from the batteries and isolate them saves the chance of arching.

I need to turn on the salesman's switch, otherwise my 12v system is not functional, even when plugged into shore power, however the 120Vac system is up and running, so the charger for the house batteries is working.

A couple of years ago I posted a question about a hot relay. CHBoone posted a reply, giving a link to a trouble-shooting guide for the Battery Control Center. I just re-read the "Battery Interconnect Function" part of that guide, and it seems that, when the COACH batteries are charged to 13.2vdc or greater, a "Comparator" circuit turns on a relay, connecting the coach batteries with the chassis batteries, enabling both sets to be charged together.
If the Comparator reads 13.2vdc on the coach side and ZERO-vdc on the chassis side, I have to assume that it turns on the relay, feeding 13.2vdc to the chassis electrical system, thereby energizing the chassis system as it tries to charge the chassis batteries. This is likely the source of my power to the CB radio, map lights, cigarette lighters, ignition, rear-view camera monitor, and headlight switch.
I further suspect that, although I am reading the charging voltage in the chassis system, the relay likely limits the amperage, therefore, turning on a high-draw item like the headlights, probably draws down all the current in the system.
Although I'm making quite a few assumptions here, I suspect this may be the 'gremlin' in my system. It's working as its supposed to work, albeit, without the chassis batteries being connected, there isn't much power energizing the chassis electrical system, but it IS energized.
Thanks again to CHBoone for the link to the trouble-shooting guide a couple of years ago. It is full of great information.