RV Furnace Runs With Thermostat Off (Fan Keeps Running)

It is a matter of time. When you buy an RV or travel trailer, you may think you have the perfect unit to camp in. However, it is just a matter of time before something goes wrong. When it does, it usually happens at the wrong time and you may have to suffer through a cold night.

There are many sources for this situation. One of them is the innocent act of bumping the thermostat. It seems that a little bump can move the thermostat just enough to allow the blower fan to kick on. Or there is a delay built into the device that keeps it running for a bit.

To learn more about this situation just continue to read our article. It explores the topic so you can have the best information possible to follow when you are in the same predicament. Take a minute or two to get up to speed on this important issue.

Why Does My Furnace Turn on When The Thermostat is Off?


The first issue that creates this situation is that there is a short somewhere. It is possible as the wires are placed in positions that keep them close to each other. This can result in altering your furnace blower fan operation.

It can also result in something sticking as a good whack has been known to set the situation right again. If something is sticking, it could be due to a short in the 12-volt positive wire. That will send a message to the control board that heat is required even when the thermostat is turned to the off position.

Sometimes, like the Atwood design, the furnace is designed to run the blower until the thermo-heat relay has cooled enough for the blower to turn off. The blower may turn off eventually once everything is cooled.

Then, it is a possibility that there is a demand for heat coming from somewhere in the system but you may have run out of propane. The blower and the furnace want to produce heat but it can’t as there is no fuel to produce that heat with.

Then, there may be a problem with the control board. If it has gone bad or there is a short somewhere, the blower fan can keep running and running until you throw the breaker. A good multi-meter should help you diagnose if that is the case or not.

Also, there could be some gelling of any oil products in the system. That reaction could have the switches sticking because they cannot move due to the gelling of the oil. A little heat should solve that problem.

RV Furnace Runs With Thermostat Off


The first place to check would be your thermostat. If it has gone bad, then you will most likely have to replace it. You could try repairing the thermostat but that may not work to your satisfaction and it could break down once again.

If the thermostat is not defective, then there may be a short in the thermostat leads. You would need a multi-meter to help you identify the problem and its location. Unfortunately, those are not the only two sources for this issue.

You could have a bad relay that you have to track down and replace if it is the culprit. If you are not good at working with electronics, and there is no shame in that, you should take your RV or trailer to someone who you can trust and is an expert on these matters.

Some owners have found that it was a bad control board and not everyone can diagnose these problems well enough to make the distinction between the different parts and which one has gone bad.

This is not a problem to wait to fix as the short cold drain your batteries and leaves you in a tougher situation. Usually, pulling the fuse will cut the power drain and give you time to get to a repairman. Also, watch out for potential fire hazards when you have this problem.

RV Furnace Fan Keeps Running


In some RV models, the fan or furnace is controlled by the ignition control unit and that may be the source of your problem. Or it may not be, The ignition control unit controls the fan and activates the sail switch, which in turn allows the igniter and gas valve to get the heat going.

Then when the room is heated to the set temperature level, the ignition control unit cuts the power and the fan works off a time delay to cool everything down. That is if everything is working properly.

If the problem is not with the unit, then you can look to other parts. One may be the sail switch has gone bad on you. When this switch is defective, it can prevent the furnace from turning the gas control valve on. You get the fan but no heat.

Or the gas control valve has gone bad, in which case you won't have any heat or fuel to power the furnace. Finally, the thermostat may be bad. If you are not great at diagnosing electrical issues and parts, then get someone who is. Or call the dealer to handle the problem for you.

They will have the necessary tools to find and replace the defective parts. The issue may be in the blower motor as well.

Some Final Words

This is a common problem that many owners experience at some point in their RVing life. It is not a difficult problem to fix. It is just difficult to find the real source. The best thing to do is if you are under warranty, take it to the dealer and let them handle the situation.

If you are not under warranty, then find an expert electrician. They know RV furnace setups. Let them handle it for you. Sometimes calling in an expert is the best way to go.

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