Furnace fan is not turning on

[Hotrizzle]

I turn the heat on on my thermostat and I hear 2 clicks for sure. One at the main ac unit and one under the stairs at the location of the furnace. After that there is nothing. The fan for the heater never turns on so I my furnace is not turning on! Any help would be appreciated. I am very capable of fixing and replacing parts my self just really not sure what to start with. I have a 2013 big country 3450ts

 

[danemayer]

Hi Hotrizzle,

The click overhead at the A/C unit indicates the thermostat has successfully signaled the relay to provide power to the furnace board, which should start the blower. You'll want to check at the blower to see if it's getting 12V. Could be a loose wire somewhere, or a bad furnace board.

Gary Brink's Furnace Troubleshooting Guide might be helpful to you.

 

[JanAndBill]

I turn the heat on on my thermostat and I hear 2 clicks for sure. One at the main ac unit and one under the stairs at the location of the furnace. After that there is nothing. The fan for the heater never turns on so I my furnace is not turning on! Any help would be appreciated. I am very capable of fixing and replacing parts my self just really not sure what to start with. I have a 2013 big country 3450ts

Just went through this a month ago with our BH. First check ALL YOUR 15 AMP FUSES Apparently whoever labels the fuses and the one that installs the fuse block are two different people with different ideas, because mine were swapped. I thought my fuse was fine but I was looking at the wrong one (mislabeled). If your fuses are ok, pull your outside furnace cover to access the wiring for the furnace. There are 4 wires, a hot wire, ground wire and two thermostat wires. You should have a constant minimum of 12 volts on the hot wire.Unless the board senses power on this line, it will go into reset mode. If you do, then with the power and ground hooked up to the furnace, touch the two thermostat wires from the furnace together, if the furnace comes on you have a wiring problem inside or a bad thermostat. If it doesn't then pull the control board and take it to a dealer with a checker that can verify the board is good or bad. Make sure their tester can test the burner AND fan function. The fan relay on my board was bad, which caused the fuse to blow. If it's not the board then you'll need to pull the furnace so it can be bench tested.

 

[Hotrizzle]

Just went through this a month ago with our BH. First check ALL YOUR 15 AMP FUSES Apparently whoever labels the fuses and the one that installs the fuse block are two different people with different ideas, because mine were swapped. I thought my fuse was fine but I was looking at the wrong one (mislabeled). If your fuses are ok, pull your outside furnace cover to access the wiring for the furnace. There are 4 wires, a hot wire, ground wire and two thermostat wires. You should have a constant minimum of 12 volts on the hot wire.Unless the board senses power on this line, it will go into reset mode. If you do, then with the power and ground hooked up to the furnace, touch the two thermostat wires from the furnace together, if the furnace comes on you have a wiring problem inside or a bad thermostat. If it doesn't then pull the control board and take it to a dealer with a checker that can verify the board is good or bad. Make sure their tester can test the burner AND fan function. The fan relay on my board was bad, which caused the fuse to blow. If it's not the board then you'll need to pull the furnace so it can be bench tested.

Thanks for the info I Will try that when the rain lets up a little bit and let you know what I find out

 

[hoefler]

First thing I would check, has a wasp built a nest in the furnace not allowing the blower motor to spin?

 

[JanAndBill]

Hi Hotrizzle,

The click overhead at the A/C unit indicates the thermostat has successfully signaled the relay to provide power to the furnace board, which should start the blower. You'll want to check at the blower to see if it's getting 12V. Could be a loose wire somewhere, or a bad furnace board.

Gary Brink's Furnace Troubleshooting Guide might be helpful to you.

Dan I've heard the relay in the A/C mentioned before, but I'm not sure that it has anything to do with the Gas Furnace. There is a 12 volt power line coming off the fuse block going directly to the furnace Module, that is always hot. There is one thermostat line that clips (piggyback) to the power lead at the board and one thermostat line going to the board. There are no relays anywhere between on the thermostat wires that I saw. When the thermostat closes it completes a circuit that energizes the brain portion of the board. After it runs all it's checks, it closes the fan relay on the board which allows power to flow to the wire feeding direct to the blower. Once the air flow activates the sail switch, the board activates the gas relay and the igniter. The combustion sensor checks for ignition. As long as you have power and gas connected to the furnace, you can connect the two thermostat wires together and the furnace will run until you disconnect them.

 

[danemayer]

Dan I've heard the relay in the A/C mentioned before, but I'm not sure that it has anything to do with the Gas Furnace. There is a 12 volt power line coming off the fuse block going directly to the furnace Module, that is always hot. There is one thermostat line that clips (piggyback) to the power lead at the board and one thermostat line going to the board. There are no relays anywhere between on the thermostat wires that I saw. When the thermostat closes it completes a circuit that energizes the brain portion of the board. After it runs all it's checks, it closes the fan relay on the board which allows power to flow to the wire feeding direct to the blower. Once the air flow activates the sail switch, the board activates the gas relay and the igniter. The combustion sensor checks for ignition. As long as you have power and gas connected to the furnace, you can connect the two thermostat wires together and the furnace will run until you disconnect them.

My understanding is that with older analog thermostats, 12V is present at the thermostat wiring and the 12V goes directly from thermostat to the furnace. On newer digital thermostats in use since around 2010 builds, there is 5V or less that operates a relay located in a box mounted with the A/C unit. That relay closes the circuit to provide 12V to the furnace. I suppose it's possible that the relay is the return/ground for the 12V circuit, but I'm pretty sure if that relay doesn't close the circuit, the furnace control board won't fire up the blower.

 

[bobw]

I see that you are located in the northern part of the country, with that in mind I would check th wiring behind the fuse panel. I work in a campground in the northeast in tne summer and have found that many times mise have made a nest their and chewed the wires.

 

[JanAndBill]

My understanding is that with older analog thermostats, 12V is present at the thermostat wiring and the 12V goes directly from thermostat to the furnace. On newer digital thermostats in use since around 2010 builds, there is 5V or less that operates a relay located in a box mounted with the A/C unit. That relay closes the circuit to provide 12V to the furnace. I suppose it's possible that the relay is the return/ground for the 12V circuit, but I'm pretty sure if that relay doesn't close the circuit, the furnace control board won't fire up the blower.

I guess it's possible that the thermostat wires from the control board extend to a relay rather then to the thermostat itself, as I didn't trace them out because I found my problem before I got to that point. However I think of the board itself as separate circuits. One circuit is the 12 volt power supply coming in that powers the fan, the igniter, and gas valve. The other powers the board which controls the fan and furnace operation. I do know that one of the "thermostat" wires draws 12 volts off the power wire right before it connects to the board, so it's sending 12 volts back up the line. When the thermostat activates it closes a connection which sends the 12 volt power back down the other thermostat wire to the board's operation circuit. The board then controls the on board relays that operate the fan,the igniter, and sends power to the gas valve relay. So part of the board has power to it all times, and part is only powered when the thermostat activates.

 

[Hotrizzle]

So I pulled the furnace out today and took it to the RV shop and they tested the board and it is good. They couldn't bench test it for me today to check the blower motor itself. They said they believe it is a 12 volt power issue and to put a battery charger on the battery and let it charge for the night. They think there is a problem with my converter. Any ideas on thst?

- - - Updated - - -

So today I pulled the furnace and had it tested they said the board was good. They think I have a 12 volt issue. Possibly a bad converter. Any thouhts on that? They suggested that I put a battery charger on for the night and see if it starts working.

 

[JanAndBill]

First thing I'd do is check ALL the fuses, the Heartland employee that wired our coach, didn't pay any attention to the labels on the fuse block. I am assuming that the shop checked "all" functions on the board "including" the blower relay. If so, then pull the blower power lead off the board and apply a known 12 volt power supply to it. If it runs it's ok, plug it back up. Now disconnect the 2 blue thermostat wires coming from the furnace to the coach. Touch the two wires from the furnace side together, if the furnace comes on, then the problem is inside with your thermostat wiring. If it doesn't come on, then disconnect the red power supply wire. Run a power wire direct from your coach battery. With the thermostat wires still connected apply power to the power lead going to the furnace. If the furnace comes on then you have a problem in the power side of the wiring. If the furnace doesn't come on then disconnect the ground wire, and make sure you have a good ground to the coach. If the furnace still doesn't come on, then the problem is within you furnace.

 

[Hotrizzle]

So I had the board tested as ok previously said and the blower works. The heater even came on this morning and ran one cycle and then quit again. I touched the 2 thermostat wires toegether and heard the click but nothing else happened. The repair man suggest a 12volt problem causing the fan to not run. I still think it is a issue with the motherboard. I'm having my converter tested tomorrow to make sure it is working properly.

 

[Roller4tan]

Today I replaced the control board on my Suburban furnace with a Dinosaur brand. My fan would not start. Showed 12v at board from thermostat, but board relay not picking up. Direct wire 12v to fan motor and fan worked. After replacing the board the furnace started right up.

 

[JanAndBill]

So I had the board tested as ok previously said and the blower works. The heater even came on this morning and ran one cycle and then quit again. I touched the 2 thermostat wires toegether and heard the click but nothing else happened. The repair man suggest a 12volt problem causing the fan to not run. I still think it is a issue with the motherboard. I'm having my converter tested tomorrow to make sure it is working properly.

Ok, I'm assuming that the two thermostat wires you touched, we're the ones at the furnace.? If so measure the voltage of the red power wire coming in from coach. It should read 12 volts MIN and nothing less. If it measures 12 volt or more, pull the red blower wire from the board and run a jumper wire from the power in lead. If the blower comes on your board has a bad relay