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. Today he discusses a heater fan.
I have a 2005 Jayco Jay Feather. The furnace blower runs 24/7 but if I pull the fuse it shuts off the refrigerator, AC and heater. I do not plan on using the heater due to its age and not knowing its history. I am a retired FF0 so know the dangers. How do I shut off the heater fan and leave others running? —Steve
First, let’s break down how each of the appliances you have described are powered and what “fuses” might be involved. If the refrigerator is an absorption-type model, it will run on 120-volt AC or LP with both requiring a 12-volt DC house battery power. On the AC side, there is a circuit breaker in the main distribution panel that is dedicated to the refrigerator only. If you shut this circuit breaker off, it will only disable the 120-volt side of the operation.
Typically there will be 12-volt DC fuses in the distribution panel, as well, and there is an automotive-style fuse for the refrigerator. Again, it is only wired to the refrigerator. On the back of the refrigerator in the module board is an inline fuse for both the 120-volt and 12-volt operation.
The roof air conditioner only operates on 120-volt power and has its circuit breaker in the distribution panel dedicated to the roof AC.
And finally, the heater, which typically operates on LP with power coming from the 12-volt house batteries, has an automotive fuse in the distribution panel. Pulling this fuse will stop 12-volt power to the furnace but cannot have any effect on the 120-volt operation of the AC unit. I wonder what fuse you are pulling that seems to shut off all three?
Back to the main issue regarding your heater fan
Let’s look at the main issue: The furnace blower runs all the time. This could either be a setting on your thermostat or it could be a faulty thermostat. Most have a setting for “Fan Mode,” which would run all the time, or heat.
This thermostat controls both the furnace and the roof AC, and some models do have a fuse inside the case. If you pulled this, it would disable the roof AC and the furnace, but would not affect the refrigerator. The “Fan Mode” setting is controlling the fan only when the furnace comes on. Having the fan on all the time moves the air.
If you could provide a few more details on what fuse you are pulling and verify if the refrigerator is actually shutting off or if it might just be getting to the set temperature and shutting off coincidentally at the same time, I could give you a more precise answer.
However, in the meantime, you should be able to pull the 12-volt automotive fuse in the distribution panel just for the furnace.
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