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Medallion power source


Xlr8ting1
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I had to bring my '09 Dynasty to a shop near Portland for an annoying check engine, stop engine, ATC issue. While there, the house batteries ran down to a couple volts. I requested they keep it plugged in, which they didn't do.  The tech said I needed a new large solenoid. I think its what's referred to as a big boy. So after a week or so of waiting for the part to show up and getting it installed, they tell me we have no instruments or dash lights (as in fault indicators, the Medallion system). The engine appears to start without them activated. Does anyone know for sure if the 12 volt Medallion system is powered from the house batteries? The tech seems to think they should be tied to the chassis batteries. Sounds plausible, but I wonder if they could have been powered from the house batteries. I've had the coach 10 years and know that in that time its never been rewired. I looked at schematics and really couldn't find out much. Electronics is not being my strong suit. Once this is resolved we can get back to the original issue. 

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You have a chassis multiplex coach.  Monaco had a HUGE battery parasitic load problem with this system so they made a mid production change to basically reconfigured the Rear Run Box (RRB) so that only the engine ran off the chassis batteries and ALL dash controls and gauges were powered from the house batteries. 

Yep, unbelievable but that's what monaco did. 

The chassis battery parasitic load was so bad that in a day or two the chassis batteries would be dead from just sitting with the ignition off. 

That is because the front and rear multiplex chassis CCM modules needed to be always powered with the ignition off to run functions like auto leveling. 

So, to solve the problem, Monaco just configured these modules to run on only the house batteries. 

In the download files there are schematics of how to configure the rrb to use the original vs the modified version with a chassis multiplex coach.

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BTW, the first thing to do if you see an ATC light is to change fuel filters.  If the transmission is not seeing the expected engine power at a given throttle position, it will deactivate ATC and turn on the light.  Lower actual vs engine ECM targeted fuel delivery pressure will also turn on a check engine light.  So, the first thing to do is to change fuel filters when these lights come on.  If you've already done this, then it's time to read codes.

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I spoke with the tech this morning. I'm having him replace both fuel filters, and cut them open to see if there might be an algae problem. Earlier he gotten 30+ codes all with the throttle position sensor. The shutdown we encountered usually didn't happen until we were about an hour underway and it never came back after putting a couple thousand miles on. When it sat for a month or two it would resurface again and shut down and it cleared itself within a few seconds, if there was enough momentum and I pulled my foot off the accelerator. An annoyance at best, but this last trip it quit 3 times in the first ten miles and showed up again after 400 miles or so. The worst was when it quit while passing a string of trucks going up the Siskiyous. Not enough momentum to have it clear itself on time. I made the decision to have it repaired before we came home. We had to fly home for a funeral and a wedding and don't have the ability to visit the shop. We are usually in daily communication on the phone. I appreciate all the info you gave me. Hopefully soon they'll have the problem resolved along with a few other squawks that it needed to be addressed. Thanks again for the info.....Theo

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