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Robert
Robert, RV Mechanic
Category: RV
Satisfied Customers: 12178
Experience:  18 yrs. RV experience including Cummins North West, Country Coach, Monaco Coach - vendor certified.
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I have a problem with my furnace not shutting down or my fan

Customer Question

Hi I have a problem with my furnace not shutting down or my fan not shutting off when thermostat is set to call for heat but all my fan air-conditioner options work on off hi and low try replacing thermostat and it's not the issue would this be my control board
Submitted: 5 months ago.
Category: RV
Expert:  Robert replied 5 months ago.

HI my name is Robert...

SO are you talking about only the furnace? You mention fan which the furnace has but so does the AC unit... OR they are both not shutting down the AC fan and furnace fan?

Robert

Customer: replied 5 months ago.
I was just talking about the options that are on the thermostat
But both fans are running but the furnace fan and heat will not shut off
Customer: replied 5 months ago.
The heat won't shut off and the AC unit fan will not shut off when call for heat
Customer: replied 5 months ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Robert replied 5 months ago.

OK

SO.... Normally when the furnace will not shut down it is the circuit board on the furnace or a time delay relay, on newer models the time delay relay is part of the circuit board older models have a time delay relay, what I find odd is the AC is doing the same thing which leads me to believe that the circuit board inside the AC unit is at fault. What is the make and model of the frnance and do you have a volt meter?

Robert

Customer: replied 5 months ago.
It is the new type
Dometic control board number part number(###) ###-####000
Note the ac/fan will shut off when thermostat is off but furnace will remain on but when called for heat bothe will remain on
Expert:  Robert replied 5 months ago.

OK

DO you have a volt meter and what is the make and model model of the furnace?

Robert

Expert:  Robert replied 5 months ago.

I am thinking the circuit board on the furnace could be at fault however it also could be the control box for the AC unit. IF you do not have a volt meter I would have a RV shop test the circuit board with a tester, most RV shops have the testers and some will even check them for free. IF the board checks out good on the furnance then I would replace the control box inside the AC unit since you replaced the thermostat. Robert

Expert:  Robert replied 5 months ago.

HI.... I see you have not selected a rating, if you still need more help please let me know, I am around daily and respond when I can.....

Robert

Customer: replied 5 months ago.
I'll get a volt meter can u tell me how to go about it
Expert:  Robert replied 5 months ago.

I am going to need the make and model of the furnace.

Normally you will have a blue wire going to the circuit board from the thermostat, when the thermostat is off you should have no power on that blue wire at the circuit board for the furnace. IF you do not have voltage then the board most likely is at fault OR if you have that time delay relay, if you have voltage then normally the thermostat is bad. I also want to dig a little deeper into the control box for the AC unit and see if that can possibly be at fault...

Robert