No 12 volt power in main slide and rear.

[FairWeatherFarm]

Can anyone point me in the right direction? Zone 3 has no 12volt power. Fuse is good. Board has power behind it and no loose wires there. All push lights connections are tight. Both switches connections are tight (no power at the switches) I'm thinking I may have to drop the entire underbelly to trace the wires to find the loose connection. You're my last hope. Has anyone had the issue before?

Zone 3 is just my main living room slide and the 4 lights at the rear of my rig. 110v power is fine.

2020 Montana 3781RL

[Daryles]

Have you already downloaded a copy of

Keystone wiring color code KRV_12_VDC_Wire_Tech_Toolbox_Oct20b

https://keystone-rv-dealer-app.cdn.p...box_Oct20b.pdf

Have a look at your DC negative (white) wire bus bar behind your circuit breaker panel.

[Van the traveling man]

Did you ever resolve this issue? I just started having this exact problem. I'm at a loss. How can the DC work when on shore power, but I lost an entire leg when disconnected?

It looks like my batteries aren't recharging either. Think replacing the automatic battery charger will help? I

[Daryles]

Originally Posted by Van the traveling man

Did you ever resolve this issue? I just started having this exact problem. I'm at a loss. How can the DC work when on shore power, but I lost an entire leg when disconnected?

It looks like my batteries aren't recharging either. Think replacing the automatic battery charger will help? I

Sounds like your red 50A self resetting circuit breakers are bad.

No DC power from battery. Good when on Shore power or connected to truck via 7 way cable.
For a 5th wheel RV...
Take a multimeter. On shore power, check each post of your red 50A self resetting circuit breakers near your batteries. They should all read the same (about 12.4vdc).
Now remove shore power. Check them again.
Which ever one is NOT showing 12vdc on the post, it is bad. Replace it.
Note: charging is also possible via the 7 way cable from your tow vehicle. It could be supplying power on the same (good) side of the breaker.
Buy Bussmann 50A self resetting circuit breakers. Very reliable. You can get them at your local auto parts store.

Carl wrote the Perfect 12vdc troubleshooting flow chart:
https://www.montanaowners.com/forums/showthread.php?t=86323

While you are there, if you have hydraulic slides and Level-up, put the hydraulic system on its own 80A circuit breaker as in the picture. Lippert put out a TSB about this. You can do a search on the forum for more info.

[Van the traveling man]

I'll start debugging tonight and post when I complete the work. Thank you for the detailed explanation.

[Van the traveling man]

Just ran through the test process and I have power on both sides with and without shore power. I'm reading Carl's article now and hopefully it will enlighten me. I added a pic of my setup for reference. In not sure why uploading caused it to rotate

[Van the traveling man]

The article was very helpful. I'm convinced it it a problem with a reverse polarity fuse or breaker. This problem started right after I replaced a backup camera. In the process I'm sure that I crossed a wire in the running lights. The symptoms align perfectly: failed DC and not recharging the batteries. I have the WF 9865 which has 2 40 amp fuses. They're not blown but I tried replacing them anyway.

Do you know of any other places where I can find reverse polarity fuses or breakers?

[Carl n Susan]

The running lights are in a different set of wiring from the RV 12V wiring. Of course, it depends on what other wire you shorted with.

[BB_TX]

The reverse polarity fuses are there to protect against hooking up the battery(s) wrong. Don’t think that would be your issue. Did you use your meter to verify 12 volts on the all your fuses on your 12 volt fuse panel?

[GHallof]

Might be a long shot. But check your 12 volt disconnect. Make sure it still functions

[Van the traveling man]

I double checked it and it is functioning fine

[Van the traveling man]

I checked the voltage at every fuse on the panel and it turns out that not all of them have 12 volts. I've uploaded a picture of the panel and where there is a red light I have 12 volts. All the others with the exception of the water pump on 11 have zero. The water pump has 12 volts even though there is no light with the fuse removed.

It seems it's not as simple as 1 of four legs being out.

Any ideas?

[Van the traveling man]

I am a total newbie to these Montanas. I was doing my testing based on the battery switch by the battery. I finally ran a trace along the line going from the battery to the distribution panel only to disvover there is ANOTHER battery disconnect as bold as it can be in the utility well. A simple reset was all it took to solve what has kept me puzzled for a while now.

Boy do I ever feel silly, but I'm good to boondock again without the darn generator. Thanks to all who helped with ideas for tracking this down.

[BB_TX]

What you are describing is not normal. A red indicator light indicates a blown fuse. So there should be 12 vote to the line side of the fuse but no 12 volts on the load side of that fuse.

The indicator light off means the fuse is not blown and should have 12 v to both sides of the fuse, or that there is no power to the line side of that fuse.

I have no guess as to why you are seeing what you describe. But again, not normal. Did you try checking both sides of each fuse for 12 volts?

Oops. Typed before I saw your last update. But even that doesn’t explain what you describe.