I recently had the motor in my furnace replaced by an extremely experienced RV appliance guy. When I put the furnace back in it never ran right. The fan sounded weak. But it was putting out heat so I let it go a little while. then it quit working all together. so I checked the wires to make sure I had it hooked up right and it ran for a while and then quit again. Finally,I took it back to the guy and he said the new motor is toast. the brushes are melted and he suspects an electrical problem in the coach. I know very little about the system but I hooked up a meter to the wires that supply the furnace and I get a reading that fluctuates between around 13.2 and 13.6 volts. Is this a normal reading or is it high? The batteries are about 2 years old. I have two 12 volt batteries in series. the rv is always plugged in. The water level in both batteries is, and has been, good. thanks

A fully charged 12v battery will be 12.8 or 12.9+ Vdc. If you have 2 12v batteries in series then you would have 24v which would melt the brushes, I am assuming you have them in parallel. (+,+) (-,-) 13.4v is normal to the furnace with the inverter running charging the batteries. My control panel normally reads 13.4v in charge mode for my trailer.

13.2 - 13.6 is common output from the converter.

A fully charged 12v system sitting idle is 12.6v. However, you said your rv was plugged into shore power and the converter is running. Modern converters are three staged, which will keep the batteries fully charged by supplying approximately 13.4v. This is what you are seeing. If you disconnect the converter, your batteries will drop down to 12.6v (or so).HERE is a good explanation of how 12vdc in our rv's work. Good reading.Ron

I believe what everyone is saying the voltage is not the problem.Replacement motor was defective or is could have had a drag on it like fan blades were hanging up.Make and model of your furnace? Any numbers on your old motor?

All RV systems should operate fine from 10.0 volts to 15.0 volts.Converter output between 13.2 and 14.6 volts is common and normal.I might be more concerned about the fluctuation more than the actual voltage. Voltage should be very steady in general conditions.Seems odd for a new motor to fail like that.... if it was the right motor.I think you mean the two 12v batteries are in parallel.

electrical, is 13.4 volts normal? | Good Sam Community

justme
Explorer
Nov 19, 2015
lanerd wrote:
A fully charged 12v system sitting idle is 12.6v. However, you said your rv was plugged into shore power and the converter is running. Modern converters are three staged, which will keep the batteries fully charged by supplying approximately 13.4v. This is what you are seeing. If you disconnect the converter, your batteries will drop down to 12.6v (or so).

HERE is a good explanation of how 12vdc in our rv's work. Good reading.

Ron

The link provide should be read because it answers the question very well and provide good education of battery/chargers.
boshog
Explorer
Nov 18, 2015
enblethen wrote:
Some rigs do not have converters, they have inverter chargers.

If you Google converter and inverter they both are defined to provide the same services based on the context, for example, as used in a solar power station.

Traditionally, an inverter is used to change DC to AC and a converter is used to change AC to DC.
enblethen
Nomad
Nov 18, 2015
Some rigs do not have converters, they have inverter chargers.
Old-Biscuit
Explorer III
Nov 18, 2015
Jim-Linda wrote:
omextreme wrote:
Jim-Linda wrote:
omextreme wrote:
A fully charged 12v battery will be 12.8 or 12.9+ Vdc. If you have 2 12v batteries in series then you would have 24v which would melt the brushes, I am assuming you have them in parallel. (+,+) (-,-) 13.4v is normal to the furnace with the inverter running charging the batteries. My control panel normally reads 13.4v in charge mode for my trailer.

Inverter doesn't charge batteries, converters do.

Jim

You know I even proof read this post 2x... still crossed inverter and converter... Guess i spent too much time this past weekend chasing an inverter problem in a buddys Newmar Coach... must be on the brain.

But thanks dont want to confuse those reading the thread.

My pleasure

Some inverters DO have chargers.......
Mine has a 3 stage 'smart' charger which I use vs my converter for charger.
Jim-Linda
Explorer II
Nov 18, 2015
omextreme wrote:
Jim-Linda wrote:
omextreme wrote:
A fully charged 12v battery will be 12.8 or 12.9+ Vdc. If you have 2 12v batteries in series then you would have 24v which would melt the brushes, I am assuming you have them in parallel. (+,+) (-,-) 13.4v is normal to the furnace with the inverter running charging the batteries. My control panel normally reads 13.4v in charge mode for my trailer.

Inverter doesn't charge batteries, converters do.

Jim

You know I even proof read this post 2x... still crossed inverter and converter... Guess i spent too much time this past weekend chasing an inverter problem in a buddys Newmar Coach... must be on the brain.

But thanks dont want to confuse those reading the thread.

My pleasure
omextreme
Explorer
Nov 18, 2015
Jim-Linda wrote:
omextreme wrote:
A fully charged 12v battery will be 12.8 or 12.9+ Vdc. If you have 2 12v batteries in series then you would have 24v which would melt the brushes, I am assuming you have them in parallel. (+,+) (-,-) 13.4v is normal to the furnace with the inverter running charging the batteries. My control panel normally reads 13.4v in charge mode for my trailer.

Inverter doesn't charge batteries, converters do.

Jim

You know I even proof read this post 2x... still crossed inverter and converter... Guess i spent too much time this past weekend chasing an inverter problem in a buddys Newmar Coach... must be on the brain.

But thanks dont want to confuse those reading the thread.
Old-Biscuit
Explorer III
Nov 16, 2015
A few things stuck out in your post:

*an extremely experienced RV appliance guy
*never ran right. The fan sounded weak.
*took it back to the guy and he said the new motor is toast. the brushes are melted and he suspects an electrical problem in the coach

I question the first statement due to the other statements.

Wrong motor or not installed correctly cause the 13.4 voltage did not cause issue

When connected to AC shore power converter should have 13.2V DC output at minimum or it is not functioning correctly. And when charging batteries 14.4V DC is common.
Your trailer DC System was not cause of 'burnt up motor'

That *extremely experienced RV appliance guy* should have known that.
YC_1
Nomad
Nov 16, 2015
SkiSmuggs wrote:
I have two GC2 6 volts in series for 12v. When the furnace in running without being connected to shore power, my voltage reading often drops below 12v until the furnace shuts down, then returns to the original charge which, when full, is 12.7-8. You can only get accurate battery voltage readings with no charging or no load for a period of time.

I would check the specific gravity. The heater draws 6-8 amps and should not pull the voltage down so far.
SkiSmuggs
Explorer
Nov 16, 2015
I have two GC2 6 volts in series for 12v. When the furnace in running without being connected to shore power, my voltage reading often drops below 12v until the furnace shuts down, then returns to the original charge which, when full, is 12.7-8. You can only get accurate battery voltage readings with no charging or no load for a period of time.
YC_1
Nomad
Nov 16, 2015
I think your clue is that it did not sound right when you put it back in. It was bad from the start. You do need to make the measurement with it running so there is a proper load on the wire.