12V lights and Systems not working...

BGINTN

Member
Having problems with all 12V systems when disconnected from Shore power or genset... I read the latest 12V block diagram & diagnostics V2 dated 9/14/20
Thought I found the answer on page 8... "Reset the Manual Circuit Breaker on the 12V buss bar"... I found the buss bar thanks to the pictures but not one of the 12V circuit breakers near the battery had a manual reset button... Is there another location for the reset button or an inline fuse that is popped or another issue altogether?IMG_5887.jpgIMG_5894.jpgIMG_5887.jpgIMG_5889.jpgIMG_5890.jpgIMG_5891.jpg
 

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6.7LMegaCab

Well-known member
Just FYI - not all RVs came with the manual reset circuit breaker. Mine didn't. I experienced issues you described and it just so happen to be because of that automatic breaker for the battery. It failed. You can take a multimeter with the negative lead to ground and red to either side of the contacts of that breaker. The battery side you should get battery voltage and the converter side, should be much lower if not at 0 without shore or Gen power.

This was hard for me to figure out as it took me a week to determine there was a problem while out camping and a few more days and help with this forum to isolate it to that breaker. The new replacement breaker I installed does have a manual reset.

Edit:

Also, the reason the battery indicator on the panel shows full charge with A/C power is because the converter is doing what it's supposed to do, but the power isn't getting to the batteries, so when you cut off A/C power, the battery indicator drops to what the batteries are showing.

Sent from my SM-G781U using Tapatalk
 

Roller4tan

Well-known member
The small black manual reset button is usually in the buss bar side opposite from the large gauge wire to the battery.
 

travelin2

Pennsylvania Chapter Leaders-retired
Check that all battery connections are clean & tight. Also where the negative grounding cable attaches to the frame
 

wdk450

Well-known member
Look for the biggest size wire coming out of 1 of the circuit breakers to identify the wire from the converter/ circuit fuse box to the battery buss bar. That should identify the circuit breaker in question.

With no shorepower and a voltmeter taking readings on all of the load side (not buss bar side) connections should show if any of the circuit breakers are open. You should have 12 volts DC from the battery on all of these load side wire terminals. If not, that breaker is open.
 

BGINTN

Member
Thank you all.

With shore power off, all 4 breakers were showing zero Volts on the load side AND on the buss bar side... so does that means all 4 are open and defective?

On another check, with shore power off, I used the remote switch to turn on the inverter and the 120V refrigerator came back on, but no other 12V lights worked.

BGINTN
 

wdk450

Well-known member
Buss bar side should be 12 volts HOT from the positive battery terminal with shorepower removed. Do you have a battery cutoff switch? This would remove the power to the buss bar.
 

BGINTN

Member
Buss bar side should be 12 volts HOT from the positive battery terminal with shorepower removed. Do you have a battery cutoff switch? This would remove the power to the buss bar.
Actually have 2 battery cutoff switches - 1 in battery compartment adjacent to the Inverter and a second one in the storage area, it is labeled "house battery shutoff"... I retested each breaker, shore power off, and both cutoff switches in the "on" position and then both in the "off" position. Still read zero on both sides of each breaker regardless of the cutoff switch position.
 

david-steph2018

Well-known member
Having problems with all 12V systems when disconnected from Shore power or genset... I read the latest 12V block diagram & diagnostics V2 dated 9/14/20
Thought I found the answer on page 8... "Reset the Manual Circuit Breaker on the 12V buss bar"... I found the buss bar thanks to the pictures but not one of the 12V circuit breakers near the battery had a manual reset button... Is there another location for the reset button or an inline fuse that is popped or another issue altogether?View attachment 67153View attachment 67158View attachment 67153
With a voltmeter start at the battery and chase the voltage. If you follow the wiring and check the voltage at each point where anything is installed in line you will find where the voltage stops. Be systematic in your troubleshooting.

While you are doing this have paper and pencil, draw the circuit out while troubleshooting it will help. This will give you help now and further down the road when another issue pops up.
 

6.7LMegaCab

Well-known member
Here's my post regarding the circuit breakers from a while back.

Take a look at the first picture with the labels to get an idea of how they are setup on my RV. In the picture, you will see one that says "From Battery". If you put the NEG test lead on ground (or negative post on battery) and put the POS test lead on that circuit breaker post, you should see the battery voltage. There shouldn't be anything on that cable between the battery and circuit breaker - unless it's a long run, in which case, you might have a high amperage fuse right on the positive battery terminal that the cable is connected to.

If that CB is bad, you will have no or very little voltage on the other side of the CB that goes to the cutoff switch when you don't have shore or generator power.
 

BGINTN

Member
Thank you, especially 6.7LMegaCab and david-steph2018. I traced the circuit from the battery and mapped the circuits and devices as suggested. Would not have been able to solve it, without doing so.

It ended up being a bad 50A auto reset breaker. I traced through once and it was showing 12.70 V on that breaker so I went on to the the next device, which was my shut off switch #2, which had no voltage. The only thing between them, was a cable, so I checked the connections, re-crimped one end and checked that breaker again, this time no voltage. Replaced it with another 50A auto reset breaker for $6.00 (local RV store did not have a manual reset breaker but I may get one online). All 12V systems are functional with no shore power or gen set running.

What a great education on tracing and trouble shooting 12V systems. Would not have been able to do so without the help of the many contributors to this forum.

THANK YOU, ONE and ALL!

BGINTN
 

david-steph2018

Well-known member
Now that you have this fixed, finish your drawing. Find out how the wiring is from the 50-amp breaker to the buss bar and to what those feed. This way you will be ahead when the next issue crops up; you will have better knowledge of your systems.
 
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