No 12v even when on shore power

[Arkman]

I have a travel trailer that that just lost the 12v lights and stereo...but the heater comes on. I have a dual battery set up and it’s fully charged, so it’s not the batteries. I checked for fuses underneath the trailer but didn’t see any with any breakers or resets. When I’m plugged into shore power, still no 12 V. Lights or stereo. Everything else works when plugged in however.. AC, refrigerator. I’m confused. I double checked my battery Killswitch but it’s working fine. All the fuses and breakers seem to be fine as well? Any help would be greatly appreciated!

[Danwilly]

Its a fuse.

[Bama Rambler]

Welcome to FRF.

You say "All fuses and breakers seem to be fine..." Did you actually test the fuses in the panel with a tester or meter? A lot of times they will 'look' good, but be blown.

If you did test them, then I'd start looking for a loose or broken wire near the power panel.

[TheWolfPaq82]

Possible Converter gone bad ??

[Arkman]

I replaced the fuses with new ones.. no go.

Thanks for the help... still looking for the culprit

It would help if I knew what I was doing..haha

[llr]

What "heater" are you refereeing to? If this is the furnace then you have some 12v working? If it is the fireplace you may have no 12v at all.

Does the water pump or roof vent fan work? These are 12v too.

[Larry-NC]

Originally Posted by Arkman

I have a travel trailer that that just lost the 12v lights and stereo...but the heater comes on. I have a dual battery set up and it’s fully charged, so it’s not the batteries. I checked for fuses underneath the trailer but didn’t see any with any breakers or resets. When I’m plugged into shore power, still no 12 V. Lights or stereo. Everything else works when plugged in however.. AC, refrigerator. I’m confused. I double checked my battery Killswitch but it’s working fine. All the fuses and breakers seem to be fine as well? Any help would be greatly appreciated!

This is a shot in the dark, given your minimal description.
Follow the positive wire from your batteries. It could be:

• The red one if the other one is black
• The black one if the other one is white

Lie on your back under the trailer and you will see that the wire goes through a little box like the one pictured below. It might be inside a flexible plastic cover. It's a circuit breaker. On the end is a tiny button. Press it.

[Arkman]

Originally Posted by llr

What "heater" are you refereeing to? If this is the furnace then you have some 12v working? If it is the fireplace you may have no 12v at all.

Does the water pump or roof vent fan work? These are 12v too.

Yes, it’s the furnace...so some 12v then?

[Arkman]

Originally Posted by Larry-NC

This is a shot in the dark, given your minimal description.
Follow the positive wire from your batteries. It could be:

• The red one if the other one is black
• The black one if the other one is white

Lie on your back under the trailer and you will see that the wire goes through a little box like the one pictured below. It might be inside a flexible plastic cover. It's a circuit breaker. On the end is a tiny button. Press it.

I found something close but it has no reset..

[TitanMike]

Originally Posted by Arkman

I found something close but it has no reset..

The reset button is small and often hard to see. Sometimes looks like part of the base. Giveaway is that it's only on one end.

If absolutely no reset, try bypassing the circuit breaker temporarily with a jumper or just remove one wire and connect to other terminal with remaining wire. TEMPORARILY, just long enough to test.

[CedarCreekWoody]

Originally Posted by Arkman

I found something close but it has no reset..

Does it have power on both sides? Either side? Check with a tester and follow the circuit.

[boondocking]

Originally Posted by Arkman

I found something close but it has no reset..

Originally Posted by TitanMike

The reset button is small and often hard to see. Sometimes looks like part of the base. Giveaway is that it's only on one end.

If absolutely no reset, try bypassing the circuit breaker temporarily with a jumper or just remove one wire and connect to other terminal with remaining wire. TEMPORARILY, just long enough to test.

It cannot be the inline circuit breaker, there would be nothing working that operates on 12 volt if it were a defective circuit breaker. According to the OP some 12v stuff is still powered. Check that all the wires are tight at the circuit breaker/fuse panel.

[Arkman]

Originally Posted by boondocking

It cannot be the inline circuit breaker, there would be nothing working that operates on 12 volt if it were a defective circuit breaker. According to the OP some 12v stuff is still powered. Check that all the wires are tight at the circuit breaker/fuse panel.

Everything at the fuse/breaker panel looks fine. I can’t find any loose wires.

[Larry-NC]

Originally Posted by Arkman

Everything at the fuse/breaker panel looks fine. I can’t find any loose wires.

Do you have a multimeter? Voltmeter? Even one of those 12v test lamps?

Go to the distribution board (fuse panel). If it's a meter, set the meter to the 20 Volts DC scale.
Put one lead on the big, heavy ground block.Take the other lead and run it alongside each fuse and contact the metal clip that holds a fuse leg. (It doesn't matter which leg.) You should see around 12.5-13.6 volts DC on the meter.
Then do the same thing, and make sure each fuse measures voltage.

The power is distributed on this fiberglass board by copper traces on the board This tests for breaks in the copper. If all the working fuses and all the non-powered ones break into two neat clusters, it is pretty likely that a break has occurred.

This is a pretty unlikely occurrence but stranger things have happened.

[Arkman]

Originally Posted by Larry-NC

Do you have a multimeter? Voltmeter? Even one of those 12v test lamps?

Go to the distribution board (fuse panel). If it's a meter, set the meter to the 20 Volts DC scale.
Put one lead on the big, heavy ground block.Take the other lead and run it alongside each fuse and contact the metal clip that holds a fuse leg. (It doesn't matter which leg.) You should see around 12.5-13.6 volts DC on the meter.
Then do the same thing, and make sure each fuse measures voltage.

The power is distributed on this fiberglass board by copper traces on the board This tests for breaks in the copper. If all the working fuses and all the non-powered ones break into two neat clusters, it is pretty likely that a break has occurred.

This is a pretty unlikely occurrence but stranger things have happened.

I don”t have that equipment but my buddy does.. I’ll get it tomorrow.

Thanks again for the help.

[Tom48]

Originally Posted by Arkman

I have a travel trailer that that just lost the 12v lights and stereo...but the heater comes on. I have a dual battery set up and it’s fully charged, so it’s not the batteries. I checked for fuses underneath the trailer but didn’t see any with any breakers or resets. When I’m plugged into shore power, still no 12 V. Lights or stereo. Everything else works when plugged in however.. AC, refrigerator. I’m confused. I double checked my battery Killswitch but it’s working fine. All the fuses and breakers seem to be fine as well? Any help would be greatly appreciated!

I would look for a fuse or cirsuit breaker on the Tongue under the front jst trace the Positive cable from teh battery.


Then of course be sure you have not installed batteries in error with reverse polarity. - side goes to the frame and to generator if you have one on board. + side may go to generator but ultimately goes from batteries through fuse or circuit breaker and winds up at the power distribution panel. That is the power from battery.


then power from Shore goes to Converter Charger and that feed to the Battery Positive as well as the distribution (fuse panel) panel for 12 v.


The shore power also goes to the 120 v AC breaker panel and those are much like the ones in your house.


The converter/Charger may have the REVERSE PROTECTION fuses blown. Should be two side by side 40 amp or may be 30 amp they are normally separate from the row of fuses for the 12 vdc stuff in your camper. They can pop from battery being backwards or from something taking a HUGE overload from your 12 v system while charging the batteries

[Tom48]

Originally Posted by Arkman

I have a travel trailer that that just lost the 12v lights and stereo...but the heater comes on. I have a dual battery set up and it’s fully charged, so it’s not the batteries. I checked for fuses underneath the trailer but didn’t see any with any breakers or resets. When I’m plugged into shore power, still no 12 V. Lights or stereo. Everything else works when plugged in however.. AC, refrigerator. I’m confused. I double checked my battery Killswitch but it’s working fine. All the fuses and breakers seem to be fine as well? Any help would be greatly appreciated!

No one seems to have asked the basic question. Year Make and Model of the camper. Old stuff prone to age related stuff as well as user induced stuff, Newer, that has worked recently, is more prone to be from something that has been changed recently or a somewhat different set of likely issues.


My 2004 camper had only a 30 amp "MAIN FUSE" from the batteries. poped all the time until I determined that the wire size could handle more (6 or 4 ga) and upped it to a higher amp fuse. At 50 amp I never had problems.



Old camper the charger converter was a plug in and then wired to the distribution panel, like an external charger, 2017 camper Charger/converter integrated with the distribution panel. Both had the matched pair of reverse polarity fuses that were essential to them putting out voltage. Fuse/breaker on tongue essential to battery being in the loop

[tomkatb]

In a modern rv a hand held voltmeter is necessary.

If the furnace blows then the batteries are ok or the converter is fine. Voltage on shore power should be over 13. Under 12.7 if the converter is off. It has a 110 fuse.

Power comes in from two wires from the battery and two from the converter.. You have power to the panel unless the tt is really wired goofy. All 12 volt comes from the fuses. Should be all or none.

Removing the cover And checking all fuses takes minutes. Be careful.

[Arkman]

Originally Posted by tomkatb

In a modern rv a hand held voltmeter is necessary.

If the furnace blows then the batteries are ok or the converter is fine. Voltage on shore power should be over 13. Under 12.7 if the converter is off. It has a 110 fuse.

Power comes in from two wires from the battery and two from the converter.. You have power to the panel unless the tt is really wired goofy. All 12 volt comes from the fuses. Should be all or none.

Removing the cover And checking all fuses takes minutes. Be careful.

Ok... here is the update. I unhooked the battery and plugged the trailer in to shore power. I tested each of the fuses and they all read 13.6v. So apparently it’s functioning properly?? So the furnace and the carbon monoxide monitor seem to be working on 12v but the lights and stereo are still down. Since someone asked...It’s a new trailer 2018 and has been garage kept. Where should I go from here??

[NMWildcat]

Sounds like you are still missing a fuse or resettable breaker somewhere. Might be time to call a mobile service tech.......