12v problem

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Pfun 1

Pfun 1

Well-known member
Joined
Feb 19, 2010
Posts
48
Location
northern Ill
My 2008 Forest River Lexington has 3 12v circuits. The jacks run off the engine battery. The slides and steps run off the house batteries on one circuit and everything else runs off the house batteries on another circuit. That circuit is dead. New batteries switch is on.  Works when plugged into 120v
 
It works when plugged into 120V because the 12V is cpming from the converter in that case.  There seems to be no 12V from the batteries.  As Rene stated, you probably blew the fuse between the batteries and the Distribution panel.  (That fuse could actually be a DC circuit breaker)

It is very common to blow/trip this circuit protector when replacing the batteries, especially if it's done without first removing 120V power to the converter.
 
Check your converter/charger for a pair of fuses, sometimes on the back. They are there for protection against reversed battery leads and often get blown during a battery change. These are separate from the normal circuit overload protection fuses on the regular fuse panel. If they blow, the battery is not connect.
 
Pfun 1 said:
Fuses are good can't find a circuit breaker.
Click to expand...
How did you check fuses?  Visual does not always tell much.  Check voltage on both sides of the fuses.
 
Pfun 1 said:
Fuses are good can't find a circuit breaker.
Click to expand...

Do you know what a 12 volt circuit breaker looks like? If not, they are a little rectangular block with 2 studs, some are manual reset and that will be a little tab that sticks out, usually on one end or the other.
Even if you can't see it sticking out use your finger and push it back in. They are usually between the batteries and the converter, fallow the wires from the converter to the batteries.
 
DC circuit breakers look like this.  Follow the positive lead from the house battery and, if it's there, you will find it.
 

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Verify the position of the main battery disconnect, sometimes they seem to be confusing.  Good luck.
 
Pfun 1 said:
My 2008 Forest River Lexington has 3 12v circuits. The jacks run off the engine battery. The slides and steps run off the house batteries on one circuit and everything else runs off the house batteries on another circuit. That circuit is dead. New batteries switch is on.  Works when plugged into 120v
Click to expand...

Pfun 1
Do you have "new batteries"... a "new batteries switch"... or both?

If you have new batteries are you sure that those batteries are fully charged...and that all of the wires to the "new batteries" are connected... and connected correctly?
If the house batteries are fully charged I suspect that something that needs to be connected to the house batteries is not connected... (or that something is wired/connected wrong).

BTW if you had NOT stated "Works when plugged into 120v" I would have suspected the "salesman switch".
A bad salesman switch... (or a salesman switch which is accidentally turned OFF),  is the most common cause of a "dead 12V curcuit" in RVs.
 
mel s said:
BTW if you had NOT stated "Works when plugged into 120v" I would have suspected the "salesman switch".
A bad salesman switch... (or a salesman switch which is accidentally turned OFF),  is the most common cause of a "dead 12V curcuit" in RVs.
Click to expand...
I'm not sure why this would change your mind about the so called "Salesman's Switch".  On most motorhomes, the 'Disconnect' switch the path from the batteries to the house distribution system.  It does NOT prevent the converter from feeding the system with 12V when plugged into 120vac.
 
If you have a big whomping multi-kilowatt Inverter charger (As I do) then it is connected to the Batteries direct.. NOT via the salesman (Disconnect) switch... However I don't use it to charge batteries for multiple reasons (less (I'm running the generator, long story omitted)

I use my Progressive Dynamics 9180+wizard (Factory selected and installed) cause I like the programming better... (yes that is the reason) it is connected to the HOUSE side of that switch.

Just now I'm on very limited (15/20 amp power) so the ONLY part of the RV that's connectedc to shore power is that 9180, it is a plug in model so I unplugged from the RV, plugged into an adapter cord I have (20 amp plug, 10 amp load) and that into a 100' 12ga to the Shop's 15/20 amp outlet.. IF I want to nuke dinner.. I have to go out and kick the 9180 into BOOST.
 
Just Lou said:
I'm not sure why this would change your mind about the so called "Salesman's Switch". 
On most motorhomes, the 'Disconnect' switch the path from the batteries to the house distribution system. 
It does NOT prevent the converter from feeding the system with 12V when plugged into 120vac.
Click to expand...

Just Lou
The way SMC, (Safari Motor Coach Corporation),  wired my so called salesman switch it turns OFF/ON the 12V power to the house distribution system fuse panel.... (whether the coach is plugged in or not).

However because different coaches can be/are wired differently...I have no reason to doubt that your salesman switch "does NOT prevent the converter from feeding the system with 12V when plugged into 120vac".

Mel
'96 Safari Sahara
 
mel s said:
Just Lou
The way SMC, (Safari Motor Coach Corporation),  wired my so called salesman switch it turns OFF/ON the 12V power to the house distribution system fuse panel.... (whether the coach is plugged in or not).

However because different coaches can be/are wired differently...I have no reason to doubt that your salesman switch "does NOT prevent the converter from feeding the system with 12V when plugged into 120vac".

Mel
'96 Safari Sahara
Click to expand...
I suspect that your coach has an Inverter/Charger instead of a simple Converter installation.  Inverter/chargers are most generally installed with large cables directly to the house batteries (through a large fuse, of course).  In this type installation, the 12V output from the Charger goes directly back to the battery and would, in fact, reach the distribution system via the same path established for the batteries.  It would therefore follow that it would be gated by the disconnect switch.

I may have made an erroneous assumption that the OP's coach has the simpler converter installation, which would operate as I initially stated.

My coach was delivered with just the converter.  I installed a whole house Inverter/Charger.  I now have capability of either/both depending on how I have it configured at any given time.
 
Just Lou said:
I suspect that your coach has an Inverter/Charger instead of a simple Converter installation.
Click to expand...

Just Lou
It does.
Mel
 
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