After a shore power short the 12v side of things is not working

Tross2023

2018 320S
At a campground, I noticed that the Aldi Heat, the overhead fan, and the systems check board, by chance I checked the shore power post and found the plug was mostly unplugged. I plugged it back in and all systems came back online. Home today plugged into home 30v and things are ok, UNPLUG the power from our home and the 12v systems are all OUT, no fan, no battery check, etc. I checked all the fuses on the WFCO and all are A-OK, I flipped all the breakers, and they are good to go, need a checklist of what to check to restore 12v equipment. TIA  

Sharon_is_SAM

Check the 30 amp fuse at the battery.  Make sure you are turning everything off before you unplug from shorepower.  Otherwise, when you plug back in there will be a surge that may blow the Alde 12V fuse.

Also, are you using a surge protector?

Tross2023

OH yes

pthomas745

@Tross2023 This is where a multimeter is the key tool.  You can chase this all over every circuit, but if the battery has quit, nothing else matters.  Use your meter at the battery and see what the state of charge is.

Tross2023

When the rig is plugged in the dashboard on the wall near the sink gives me 13. something volts, also, the electric tongue jack I installed still turns on and works fine. I will double check the fuse. Thanks!

Tross2023

It was the battery cut off switch! 

pthomas745

The "SeeLevel" battery monitor, or any voltage monitor, will always read...13 something for a lead acid battery when the trailer is on shore power.  A battery voltage readout when the battery is being charged is...false. It is only showing you the charging voltage coming in.    A lead acid battery readout, when the trailer battery switch is on and no charging coming into the trailer is..also false.  Depending on how much 12V power the trailer is using, the voltage can swing dramatically...and always will be "too low".

What you want is a voltage readout of the battery when it is "at rest":  no charging, no usage.  Just sitting there with the atoms and chemicals inside the battery doing nothing.  The SeeLevel won't work with the switch off....so you need a separate voltage readout device: a multimeter, a shunt, or some other device that can let you read the "rested" voltage.

Sharon_is_SAM

@Tross2023 - glad it was something simple.  It sounds like you may have towed with the battery switch off.  Good time to review for readers that you must always tow with the battery switch turned on.  The break away brake switch relies on the TaB battery to apply the brakes in case of a complete detachment.  

Tross2023

I think i was switching things on and off when we woke up and electrics were all out, but we have fixed it!