Saturday, September 30, 2023


Why does converter show 13.8 volts output but battery shows 7.1 volts?

Dear Dave,
I’m using a 12-volt battery instead of two 6-volt batteries. When I check the voltage at the lines going to the battery, I’m getting 7.1 volts. Is this correct or is the converter getting reduced to 7.1 volts because I used to have two 6-volts batteries. My converter reads 13.8 volts at the leads going out. —Ernest, 2000 Pace Arrow Vision

Dear Ernest,
Something is not right with the voltage as your converter/charger does not adjust different voltage for 6 volt or 12 volt. If you are plugged into shoreline power, the converter will put out 13.8 volts initially until the battery reaches 12.6 volts and then drops to 13.2 volts. If you have two 6-volt batteries, they should be connected in series, which is positive to negative, and gives you a 12-volt bank.

But if you only have one 12-volt battery, it should read 12.6 volts fully charged. If you are only getting 7.1 volts at the battery, somewhere the connection from the converter to the battery has an open connection which is not allowing the charge voltage from the converter to reach the battery. This would explain why you are not seeing 13.8 volts at the battery, and it has drained down to 7.1 volts as it is not being charged.

First thing to check is battery disconnect switch

The first thing I would look at is the battery disconnect switch, typically located in the entrance area. Sometimes it is down on the side of the steps or could be higher on the cabinet panel with the light switches. If the switch is in the disconnect position, it is like removing the negative post and nothing from the converter will get to the battery. It is designed to reduce a drain on the battery from a component left on during storage such as compartment lights and such. Typically, the LP leak detector is bypassed from this switch so it can still drain a battery in a matter of a few weeks.

If the switch is in the connected or closed position, then you will need to trace the cables from the converter to the battery and everything in between. There are several solenoids, ground posts, and components that could be loose or broken, or even a fuse tripped.

Look at this rat’s nest from a 2015 Thor Challenger which has several posts, fuses, and other connections. This actually had a spade-type fuse that had tripped and created an open circuit to the generator, so it was not getting power to start. It did not affect the charge from the converter; however, they are all wired different.

Good luck getting a wiring diagram

The challenge is that you will most likely not be able to get a wiring diagram, as Fleetwood has been bought by REV. I have heard most owners have not had any luck getting them. So, it will probably be a hands-on journey following the cables, unless you can find a wiring diagram online.

I would also recommend checking the actual converter, as there may be fuses on the back side. Typically, if you find 13.8 volts on the converter, the fuses should be good. But I’ve learned to never say never, or always, when it comes to RVs.

 You might also enjoy this from Dave 

Can I replace my RV’s two 6-volt batteries with one Group 27 12-volt?

Dear Dave,
I want to replace my two 6-volt house batteries with a single 12-volt deep cycle battery. Both batteries are dead at this point. The battery I’m looking at is an Interstate and I’m told it is 90-amp hours. My questions are: Will this be enough for a day’s travel using only the water pump until plugged in at night, and will the driving keep the battery charged? Thank you for your help on this. —David, 2016 Minnie Winnie 31K

Read Dave’s answer.

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

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Dave Solberg
Dave Solberg
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. He has been in the RV Industry since 1983 and conducts over 15 seminars at RV shows throughout the country.


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2 months ago

Dave, my neighbor had a similar issue several months after replacing his two 6 volt batteries. They ran down to around 3 volts while being plugged into shore power for a few months. House 12v lights dim. Meter showed the charging voltage from converter was only slightly higher than 3 Volts. Fuses all good. Removing the DC Leads from the Converter and then powering it up showed almost 14 VDC with NO LOAD. I put a standalone charger on the pair of batteries and did a slow charge over 24 hours, then disconnected. 48 hours later, I tested batteries and they were holding full voltage. I replace the Converter with a new Progressive Dynamics 4 stage Converter! Still Good 12 months later!

Neal Davis
2 months ago

Thank you, Dave!

2 months ago

Do the interior lights work when disconnected from shore power? Does the awning extend and retract? Sounds like there is an open circuit or disconnect switch is off. There also may be an auto-reset breaker on the positive wire going to the batteries.

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