No 12v DC

[RHHarrison]

I have no 12v DC thus I have no 12v lighting, no way to open the slides, no way to start the Generator, or anything else on the control panel. I have a Magnum Inverter/Charger which seems to be operating normally charging the batteries and supplying 115v for the residential refrigerator. I can start the Coach and the 12v DC returns. I have checked every fuse I can find, and all the breakers and all
are okay. New batteries installed on 4-11 and been working on this issue since.
Any idea's. What am I missing.

[Mile Marker 42]

Originally Posted by RHHarrison

I have no 12v DC thus I have no 12v lighting, no way to open the slides, no way to start the Generator, or anything else on the control panel. I have a Magnum Inverter/Charger which seems to be operating normally charging the batteries and supplying 115v for the residential refrigerator. I can start the Coach and the 12v DC returns. I have checked every fuse I can find, and all the breakers and all
are okay. New batteries installed on 4-11 and been working on this issue since.
Any idea's. What am I missing.

Sounds like salesman switch.

[153stars]

Agree with salemans SW. Near front entrance , but closes solenoid at 12v main bay/area. If solenoid is dead put both cables on one lug or bolt them together and tape up , leave a bent over flag to make easy to peel later. Some times flicking switch a bunch can help or firm tap on solenoid get you by.
2nd could be a manual house disconnect has died. Same plan works as above to bypass it.

[vsheetz]

Try the 12v switch by.the entry door. But typically slides and genny start are not controlled by it. And since everything works with engine running making the chassis battery/alternator power the coach if it was the switch lights and such would likely still not work.

That the inverter works indicates the battery bank itself is ok. The inverter/charger is often directly connected to battrry bank and not sharing the house connection to the battery bank.

Power from the house bank is being blocked to house and other functions. Bad house main disconnect switch. Large catastrophic fail fuse for the battery bank - typically a 300a ANL or similar. Cable connection.

[Arch Hoagland]

RHHarrison said:

" New batteries installed on 4-11 and been working on this issue since. "

Did the problem exist before you changed the batteries?

[SergioP]

Originally Posted by Arch Hoagland

RHHarrison said:

" New batteries installed on 4-11 and been working on this issue since. "

Did the problem exist before you changed the batteries?

^This. My guess is when they changed the batteries they left off one of the cables. There’s more than 2 or 3 cables going to the batteries, I bet one of them is hanging down in the battery box or somewhere in the area.

Once I had the negative ground cable come off at the frame and had no coach 12v. Might check that too.

[wildmanbaker]

Originally Posted by SergioP

^This. My guess is when they changed the batteries they left off one of the cables. There’s more than 2 or 3 cables going to the batteries, I bet one of them is hanging down in the battery box or somewhere in the area.

Once I had the negative ground cable come off at the frame and had no coach 12v. Might check that too.

This may be the problem.

[Persistent]

No lights
No slide power
No gen start power
Nothing works on control panel
Batteries charging
115 volts to refer

These observations are not likely. Check conditions and verify. It is unlikely batteries are charging under these conditions.

All non-working 12 volts begin working when chassis engine is started.
This means frame ground for 12 volt distribution panel is good.
This means all 12 volt distribution panel fuses are OK.
Chassis to House bridge is working OK.

Are you sure batteries are charging with RV engine "off"?

How do you know? Magnum is unlikely to charge batteries and not supply house 12 volt appliances.

Battery charging would probably come from Magnum or from Engine.
Are you plugged into shore power? Magnum will only charge if on shore power or generator power. At the same time it supplies 12 volts to house appliances.

If not on shore power or gen power, Magnum will invert 12 to 120 volts and possibly supply 120 volts to refer. Magnum charger will be "off".
If on shore power or gen power, refer will get 120 volts from shore power.
Is there another charger, maybe solar or another built in?

Please answer questions for better advice.

Battery bank connects to:
Bridge circuit to chassis
Magnum
House distribution panel

They may be connected in many ways. Follow battery connecting wires, both positive and ground.

Check connections for tightness and corrosion.

Check voltage along the way.

Voltage should be the same as battery terminal voltage. Any place voltage changes or is lost is suspect.

Plug into shore power or start gen. Check voltage on battery terminals using a portable voltmeter with the RV engine "off" for a couple of hours.

Check DC voltage on the 12 volt Magnum terminals. 12 volt terminal on Magnum should have same voltage as battery terminals.

If not, big fuse between battery and Magnum may be blown. Check voltage on each side of fuse. If voltage is different, fuse may be the issue.

Check AC voltage at the pedestal or gen, which ever is being used as the power source. Voltage at pedestal and 120 volt input and output on Magnum should all be the same.

[RHHarrison]

Found the problem. The BUSS AMG 250A 32V Fuse bad. All is well. Thanks for the heads up on the salesmen switch. Pulled it out and worked my way back.

[Arch Hoagland]

Thanks for the update, glad to hear you found the problem.

[Dav L]

Originally Posted by RHHarrison

Found the problem. The BUSS AMG 250A 32V Fuse bad. All is well. Thanks for the heads up on the salesmen switch. Pulled it out and worked my way back.

Fuses don't go "bad"...something blew it from a short. Very likely when the batteries were recently replaced someone shorted the wiring to ground...250A fuses take a direct welding / sparking short to fry.