Furnace blower pulsing when off

[Gutterball]

AFMD35111_A furnace troubleshooting.

Furnace blower is receiving a pulse signal to start every 5 seconds while the AC is on. Won't stop until fuse is pulled.

Is it reasonable to pull the entire unit out and troubleshoot on the bench?

Since it's been working for years, I assume it's a circuit board problem.

[Scott'n'Wendy]

I would verify the t-stat first prior to pulling the furnace. I haven't heard of a t-stat causing your issue, but I'd hate to pull the furnace and later find out it was a faulty t-stat

[Cate&Rob]

Gutterball

Please provide more information on the year and model of your Grand Design RV, so that replies here can be more accurate. Have a read through our Welcome information. https://gdrvowners.com/forum/main-fo...welcome-letter

An AFMD35111 furnace is an early Atwood model, so I am guessing that you have and early build RV. Do you have an external furnace access panel? If not, removing the furnace by an internal path gets complicated.

The control board for an Atwood furnace is in the associated Atwood AC unit. I would look there first, before pulling the furnace if the furnace is otherwise working correctly.

Rob

[Jlawles2]

As mentioned I would start with the thermostat or control board in the AC. You may find a pair of wires that have rubbed through creating the call for the furnace when the AC kicks on if the unit is older and has a few miles on her.