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12 Volt System Works When Coach is Running


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Can anyone help me understand why my coach only has 12 volt power when the engine is running.  I checked the house batteries and they are charged.  I’ve been reading about the infamous salesman switch going bad, but I have power on all four terminals of it.  My 12 volt fuse block that is in the bedroom above in the cabinet has power to the fuses.  I feel like it is a ground somewhere?

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Im going to assume your asking why you have 12v power and not 120v power anywhere. 
You would only have 120V power if:

- You are plugged into shore power, or

- Your generator is running, or

- You are running your battery inverter to get 120VAC

Your coach won’t have it unless one of those scenarios are met.  

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Sounds like your 12v from the house batteries is not getting to the house,  but when the engine alternator is running it is suppling 12v to the house.

Grounds could be suspect but first take a look at your battery disconnect switch.   My switches are located in my rear elect bay, next bay to the batteries.

You have 2 switches with big big round knobs.  The sw can look ok but fail inside.  Moving one wire over to the other will suffice temporarly.

 

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Does anyone have a electrical schematic for a 2008 Monaco Knight, plugged into a park 50 amp service and wham ever thing when south. no longer able to get anything to work , fault light on the inverter, not charging the batteries, How can I bypass the transfer switch or verify that it is the problem. A mobile mechanic came out and said he thought the problem was in the reel. It was not. I had to cut off my house batteries, run a jumper from my toad then things came alive, I could run my generator and the 12V circuits seemed fine. Going to check individually the house batteries for one being bad 18 months old 

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Alright guys, I hated to respond to this because I feel like an idiot.  So I checked the battery switches like “Ray Davis” said from the above response and that wasn’t it.  Then my wife said didn’t you put on a new inverter charger, maybe that’s the problem!  So when I put the new Xantrex  Freedom 458 inverter charger on, I didn’t connect one of the ground cables.  My original had a second  “vehicle chassis ground”, see pics and my new One didn’t.  Needless to say once I did that, boom, problem solved.  Geez, now I’m gonna have to make something up so my wife doesn’t think she’s smarter than me.  😂

CDDC4124-FD33-41AC-BCF1-0D6AEEF8FB0A.jpeg

9AB542AC-5ED8-44F1-9E70-EF6A50152649.jpeg

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4 hours ago, Gospel said:

Does anyone have a electrical schematic for a 2008 Monaco Knight, plugged into a park 50 amp service and wham ever thing when south. no longer able to get anything to work , fault light on the inverter, not charging the batteries, How can I bypass the transfer switch or verify that it is the problem. A mobile mechanic came out and said he thought the problem was in the reel. It was not. I had to cut off my house batteries, run a jumper from my toad then things came alive, I could run my generator and the 12V circuits seemed fine. Going to check individually the house batteries for one being bad 18 months old 

I didn't see a diagram for an 08 Knight but there are diagrams for 06  07 and 09 Knights in the downloads section.

Look at the top of this page for the white strip and select downloads then electrical and diagrams.

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Patrick, as suggested it could be the main battery shut-off switch.

Your alternator brings a "charging level voltage" online which probably engages an IRD or BIRD. These devices are designed to control the combination of the battery banks.

With the alternator (triggering this combining event), power comes parallel to the house batteries. This power is getting to your salesman solenoid and other places of course. 

There is an "OPEN" circuit from your house batteries somewhere along the line and as suggested one of those heavy-duty mechanical switches can fail. Grab a voltmeter with your engine NOT running and start following the large cables from the house batteries. Use a needle to pierce wires along the way if needed. I highly suspect you are going to find the fault close by.

With this said, a bad ground from your house batteries could give you similar symptoms. 

 

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7 hours ago, Gospel said:

Does anyone have a electrical schematic for a 2008 Monaco Knight, plugged into a park 50 amp service and wham ever thing when south. no longer able to get anything to work , fault light on the inverter, not charging the batteries, How can I bypass the transfer switch or verify that it is the problem. A mobile mechanic came out and said he thought the problem was in the reel. It was not. I had to cut off my house batteries, run a jumper from my toad then things came alive, I could run my generator and the 12V circuits seemed fine. Going to check individually the house batteries for one being bad 18 months old 

Mobile mechanic???

Since 120 is not getting to your inverter/charger it appears but could easily be verified, that you may have issues at the transfer panel as suggested. 

It only takes a couple of minutes to isolate the issue. Find the transfer panel and open it up. The problem may jump out at you.

Get the model number and post it here. There may be a schematic on the inside cover. You should be able to find 120 volts in two places inside the relay. That is, each leg of the 50 amp service that is coming in. If you measure across them you should see basically 220 volts. If you find the power is present from the power cord and you say the generator makes things work fine then the transfer relay is at fault or other mechanical connections thereabouts.

IF you find the proper voltage coming in you can wire around the relay panel if you are comfortable doing so. This would prevent power from your generator running things but would get buy you time waiting for a new transfer panel. 

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23 hours ago, Gospel said:

Does anyone have a electrical schematic for a 2008 Monaco Knight, plugged into a park 50 amp service and wham ever thing when south. no longer able to get anything to work , fault light on the inverter, not charging the batteries, How can I bypass the transfer switch or verify that it is the problem. A mobile mechanic came out and said he thought the problem was in the reel. It was not. I had to cut off my house batteries, run a jumper from my toad then things came alive, I could run my generator and the 12V circuits seemed fine. Going to check individually the house batteries for one being bad 18 months old 

The 2007 or the 2009 MIGHT be the same. You will have to look.  Each of the prints, if you download and open the files, will have, in lower right title block, some NOTES as to what years it covers. It would be a guess to say that your MH is exactly the same as either...but odds are, you have ALL the files needed between the two..

OK>>>>FOLLOW THIS....

First, NEVER TRUST the PARK's electrical system. If you have a Volt meter and know how to use it....then TEST the receptacle to insure that it is a PURE and properly wired receptacle.  Google on how to test and the voltages.  This ain't a rocket science project.

Second.  RUN THE GENNY and do THIS.

Hold on the POWER button on the Inverter case...assuming it is a MAGNUM. Hold on for 10 - 20 seconds. That RESETS the Magnum. THIS IS A MUST DO. That will also "CLEAR" out the faults or errors in the remote as well.  You MAY have to "Start" or push the ON button on the Magnum interior remote. You have to DO THIS WITH 120 AC coming in.

NOW....test or look at the outlets. Microwave blinking....boil a cup of water or heat for a minute.  Have power to the TV and an outlet around the sink? If Microwave works and no power on the outlets, you probably have blown or tripped the GFCI. Probably one in a bathroom.  Reset.

All 12 VDC lighting should be functional. If not, then the Salesman's switch got tripped or the solenoid is bad. Assume you know what that is and how to turn ON.  It is in the manual.

IF ALL IS WORKING>>> and you did not test or know how to test the AC, talk to the park folks and have them test or move to another site. 

That is all that anyone can tell you without more specifics. If you have the IOTA 50-R ATS, then it probably blew up.  That was recalled.  It needs to be replaced, bad or not, otherwise it can catch fire. The ESCO LPT50BRD is the most commonly used and reliable one.  

Bypassing the ATS is not recommended and might be needless....UNLESS you are ABSOLUTELY SURE that the pedestal POWER is CORRECT. You need to read, and perhaps you did, what the "Fault Light" on the inverter is telling you.  without knowing the brand (assumed Magnum) and which light came on....all would be a guess.  If it was on the interior remote...what was the error message.

Based on the info in your post, the above is all that anyone here can do....

Do the above.  Get verification that you have good power or move and test. If it happens again, WITH A GOOD KNOWN 50A service, then you have issues...  Give us more info and folks will try to help. Blindly or without good electrical knowledge, bypassing an ATS or "messing around" without diagnostics will cost you big buck...and if not done safely...hurt you. We DO NOT know your skill level or knowledge. 

Good Luck...

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