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RV Furnace 15 amp fuse blowing


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Hi gang - its the 'lectrical dummy here again with a situation / questions:

My base camp rig is a cold weather capable trailer with 2 furnaces.  One of the furnaces will blow it's 15 amp fuse in the load center about once every 2 weeks maybe 3.  There seems to be no set of "parameters" that causes it. 

In other words the furnace cannot be trusted when I have to leave the trailer for a day or two in below freezing weather.  

I am wondering if it is the fuses themselves.  They were bought from an "auto parts" chain - don't know if anyone has noticed lately but a lot of aftermarket auto parts seem to be pretty junky, possibly sourced for price point vs quality? 

I'm thinking I need to stop by my Kenworth dealer for some good quality fuses maybe? 

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2 hours ago, Darryl&Rita said:

Meet your new best friend:


Readily available at the orange store, the blue store, the yellow store, and Chinese Tire.

Darryl - do we think fan shafts need a drop?  They roll to a stop with nary a squeek .... 

Won't hurt I bet....

Edited by noteven
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  It could be a battery or charger issue also. Low volts high amps. It could be battery connection issue also. If you have a amp-meter check the amps. Now that bearing thing could be your real problem. Oiling may just be temporary.

  So this winter I installed a used furnace under the rv. The bearings were noisy so I installed a new motor. Darn new motor would only run maybe 15 seconds then stop. Took new motor out and rotated the old motor 180 degrees. And reassembled it. It is a suburban furnace so the wires are made so it fits one way. Extended the wires to have bearings turn 180 degrees. Furnace ran all winter till about two weeks ago. Final bearing failure.

the New furnace motor was old stock from my business probably 8 years old. So I took it apart and the positive wire solder joint failed just siting night the back of my old Jeep.


 Winter is getting to its end , I hope you get it operational,



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43 minutes ago, noteven said:

Furnace #2 is the critical one - it also supplies heat to the tank compartment. It has a ... ahem... 20amp fuse...

That is not a good idea! Something that is fused for 15A is usually to prevent excessive current to the furnace which could make your problem get worse. There are two considerations in fuse choice. One is the wire size and 14 agw is limited to 15a. The other is the safe limit of the equipment being supplied power. A fuse is a safety device and too large could damage the furnace or in worst case, cause a fire.

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In 50 years of RV ownership Ive experienced a ton of furnace problems, often (if mechanical not electrical) the blower motor often due to failed bearings. Ive tried and had limited success trying to "lube" the bearings which maybe didn't last too long.

There  might be mechanical restrictions causing a drag increasing the current,,,,,,,,,,,,,Bearings as discussed above,,,,,,,,,,,,,The motor may have electrical (instead of mechanical) problems like bad or partly shorted wiring (does it pass the electrical smell/burn test ??) ,,,,,,,,,,,,, LOW VOLTAGE (check battery voltage BOTH at battery PLUS at the motor when running)  ,,,,,,,,,,,Loose resistive voltage dropping electrical  connections,,,,,,,,,,,,Excessive line voltage drop,,,,,,,,,,Or the motor is simply bad, electrical or mechanical.

The combination of Voltage at the motor when running  PLUS an ammeter to measure the current draw could provide valuable diagnostic information 

NEVERRRRRRRRRRR use a fuse rated higher then the wires ampacity IE if its designed for a 15 amp DO NOT replace it with a 20

It seemed the colder it gets when needed the most is when blower motors fail grrrrrrr

John T

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yes JohnT -quit when needed is true isn’t it...

I don’t have the equipment but has anyone ever tested China mfg fuses for performance?

Anyways I’m off to town today I’m going to pick up some known brand 15’s.

I’ll get some test equipment attached to someone who knows how to use it to measure some volts and amps and see what is what. 

Ill report back.

Edited by noteven
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notreven, good idea to get a read on voltage levels (battery PLUS at furnace when running) and actual current draw and sure, anythings possible, but if voltage levels are okay and all connections and you're constantly blowing 15 amp fuses (even if China fuses) I doubt its a faulty fuse but a blower motor problem   


 John T

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