Just started having this issue with my 2007 Coachman with an Atwood converter. Had the RV plugged in all winter with the battery disconnected but on a Battery Minder, as I've always done before. The RV is left plugged in so that I can use the 120 volt circuits inside to keep a dehumidifier running and prevent that musty smell. The battery is left disconnected because the charger isn't 3 stage and ruins the battery if left charging all winter, whether you keep up with the water level or not.So anyway, I arrived at my campsite, and unhitch, go inside and try to use a 12 volt light. Nothing. Battery is connected, but I notice also that the fridge is off, though it was on when I left home. Thinking the battery must not have survived the winter, I disconnect it again, and pull it from the trailer. Plug in the trailer, and 12 volt works again, but with an issue: frequently when I flip on one or another light, all 12 volt goes out just for a second, then comes back on. Not every light, not always, just sometimes. Also, from time to time, one or another of the GFCI circuit breakers pops. Not when I am doing anything, and no necessarily when there is anything plugged in.Took the battery and had it tested. They said it is in great shape, tests normal, no problem.Any ideas? Should I just replace the converter? Lack of 12 volts when on just the battery is a big concern. Suggestions?

using a multimeter, do you have 12vdc coming off the converter? Is the converter even running (cooling fan)?

12 volt lights work, and appear to be normal brightness without the battery connected. No need to check with the multimeter, except perhaps to see if it's 12.6 volts or 14.4 volts. And, yes, converter fan comes on from time to time.

It's likely a connection then if the battery is in fact good, especially if it was still charged when lights didn't work. On my trailer the battery cables go inside to a PDC, a power distribution center--the place where all fuses are. I would connect battery, check for poWeR there at PDC. Check for ground at PDC. If ok, and try loosening and retightening those two power and ground cable bolts, next go to converter connections. Same thing, loosen then retighten check VoLTs at each point along the way. Even better to do all this with lights on drawing a load you may see them flicker as your working and know problem is in that area. Things get bumped around, maybe something loosened up.

battery on TTmake sure you did not hook up the wires backwardsWHITE is negative groundblk and red are hot 12v positive

Though I do not think this is exactly the problem it is related:Many RVers have a few screws loose.IN this specific case there are a few screwy suspects I will list:120 vac Distribution panel (Breaker box) Wires leading to converterGround wire (Chassis ground) on both battery and converterConnections TO converterAnd there are a number of "Other" Suspects. Like every connection in the 12 volt system battery/converter wise of the distribution panel.And finally.. One strange one I found not six feet from my feet as I type.I had one wire.. When I metered using a VOLT METER it was delivering near full battery power (Down about half a volt, kind of a high loss with a 20,000 ohm per volt meter) When I used a test light (My favorite tool) Dark, completly dark. The battery end however was full bright.This is a single piece of wire, NO splices, NO junctions, A single piece of wire, I personally ran it so i know it's a single piece.Started laying the old Mark One Eyeball on it (Visual inspectiopn) and found a bulge.. That was NOT there when I installed it.Inside was a whole lot of corrosionI excised the bad part, Soldered and sealed. and I just checked the power indicator on the Freezer it powers... Nice and Green.

The curious case of the funky 12 volt system | Good Sam Community

naturist
Nomad
Jun 19, 2016
I will look for loose connections and corrosion. Thanks for the suggestions.
westend
Explorer
Jun 09, 2016
Check your ground connections. All the symptoms you state point towards a bad/intermittent ground connection.
MEXICOWANDERER
Explorer
Jun 09, 2016
On a Dragger (trawler), I found one outside deck light with the copper conductor turned to green powder for almost twelve feet in length.

WITH A TEST LIGHT & METER The problem can be traced easily

WITHOUT TEST INSTRUMENTS Get a dart board and bottle of good whisky.
ferretgrandpa
Explorer
Jun 09, 2016
Is the battery fuse good?
I had to change one out a couple of years ago.
Trace the wires from the battery, both lines, look for any small inline device, some have a reset, some don't.
pianotuna
Nomad III
Jun 09, 2016
Where I am right now (Pike Lake, SK) there is a history of 120 volt #12 extension cords being "eaten".

At first I thought it was just bad ends--so I put on new ones. I did not have a meter at the time, but a test light refused to shine. There is no visible damage and the copper is bright and shiny. I even tried cutting off a 5 foot piece--same problem.
MEXICOWANDERER
Explorer
Jun 09, 2016
Clean the ends of + and - cables, all of them, positive, converter, battery pos and neg, frame lug and frame steel negative. Then check again.
wa8yxm
Explorer III
Jun 09, 2016
Though I do not think this is exactly the problem it is related:
Many RVers have a few screws loose.

IN this specific case there are a few screwy suspects I will list:
120 vac Distribution panel (Breaker box) Wires leading to converter
Ground wire (Chassis ground) on both battery and converter
Connections TO converter

And there are a number of "Other" Suspects. Like every connection in the 12 volt system battery/converter wise of the distribution panel.

And finally.. One strange one I found not six feet from my feet as I type.

I had one wire.. When I metered using a VOLT METER it was delivering near full battery power (Down about half a volt, kind of a high loss with a 20,000 ohm per volt meter) When I used a test light (My favorite tool) Dark, completly dark. The battery end however was full bright.

This is a single piece of wire, NO splices, NO junctions, A single piece of wire, I personally ran it so i know it's a single piece.

Started laying the old Mark One Eyeball on it (Visual inspectiopn) and found a bulge.. That was NOT there when I installed it.

Inside was a whole lot of corrosion

I excised the bad part, Soldered and sealed. and I just checked the power indicator on the Freezer it powers... Nice and Green.
MrWizard
Moderator
Jun 09, 2016
battery on TT
make sure you did not hook up the wires backwards

WHITE is negative ground

blk and red are hot 12v positive
pickjare
Explorer
Jun 09, 2016
It's likely a connection then if the battery is in fact good, especially if it was still charged when lights didn't work. On my trailer the battery cables go inside to a PDC, a power distribution center--the place where all fuses are.
I would connect battery, check for poWeR there at PDC. Check for ground at PDC. If ok, and try loosening and retightening those two power and ground cable bolts, next go to converter connections. Same thing, loosen then retighten check VoLTs at each point along the way.
Even better to do all this with lights on drawing a load you may see them flicker as your working and know problem is in that area. Things get bumped around, maybe something loosened up.
naturist
Nomad
Jun 09, 2016
12 volt lights work, and appear to be normal brightness without the battery connected. No need to check with the multimeter, except perhaps to see if it's 12.6 volts or 14.4 volts. And, yes, converter fan comes on from time to time.