Heater Fan Motor

[Travler]

I was wondering if any of yall have had your heater Fan Motor run all the time? I have the thermostat turned all the way down and it does not matter if you are running on Batt or hooked to shore power.....it runs all the time. I need to figure out what's going on. So if you have any suggestions I am all ears.

Please state your TM year/model and Furnace year/model. Does the burner also stay on? If you pull the fuse and replace it does it stop?

My new-to-me TM had that problem.
I bought a pre-owned 2002 last November and used a leaf blower to clean out all the outside vents, hatches, roof and storage.
When I got inside to test and clean everything, the furnace would sometimes cycle correctly and sometimes the fan would stay on for hours after a heat cycle.
I may have messed up or misalligned the sail switch.
I took it to an RV repair and it worked worked perfectly for them the first 6 times, then stuck on. They got me for a few hundred dollars for a circuit board.

My Suburban NT20SE furnace has 4 wires- 2 for power - 2 for thermostat.
The thermostat simply connects the 2 thermostat wires to START furnace. When wires are disconnected the furnace fire stops and fan does about a one minute cool down.
So a test is to disconnect themostat wires at the furnace and see if it cools down and shuts off - this will tell you if the themostat and/or wires to it are bad.
Just short the wires at the furnace for a while to start a cycle.

Also check is you have 12+ volts DC. Some things get flaky with low voltage.
Try disconnecting battery and unplug TM (or pull fuse) - may reset furnace.

That's all I can think of....

[Travler]

Originally Posted by LiveTicker

Please state your TM year/model and Furnace year/model. Does the burner also stay on? If you pull the fuse and replace it does it stop?

My new-to-me TM had that problem.
I bought a pre-owned 2002 last November and used a leaf blower to clean out all the outside vents, hatches, roof and storage.
When I got inside to test and clean everything, the furnace would sometimes cycle correctly and sometimes the fan would stay on for hours after a heat cycle.
I may have messed up or misalligned the sail switch.
I took it to an RV repair and it worked worked perfectly for them the first 6 times, then stuck on. They got me for a few hundred dollars for a circuit board.

My Suburban NT20SE furnace has 4 wires- 2 for power - 2 for thermostat.
The thermostat simply connects the 2 thermostat wires to START furnace. When wires are disconnected the furnace fire stops and fan does about a one minute cool down.
So a test is to disconnect themostat wires at the furnace and see if it cools down and shuts off - this will tell you if the themostat and/or wires to it are bad.
Just short the wires at the furnace for a while to start a cycle.

Also check is you have 12+ volts DC. Some things get flaky with low voltage.
Try disconnecting battery and unplug TM (or pull fuse) - may reset furnace.

That's all I can think of....

I have a 2007 2720 SD as for the furnace I will have to get back to you on that,but I will preform the above test and see what happens and then get back to you. I have already pulled the fuse and left it out for about 3 hours and put it back in and it started back running (Just the fan).

[Travler]

Originally Posted by Travler

I have a 2007 2720 SD as for the furnace I will have to get back to you on that,but I will preform the above test and see what happens and then get back to you. I have already pulled the fuse and left it out for about 3 hours and put it back in and it started back running (Just the fan).

First this is a NT20S Furnace. This what I did. First I powered down the TM....no power at all for 24 hrs. 2nd I made sure the Batt was @ 12.5VDC
3rd I removed the wires from the furnace to the thermostat. Then I powered up the TM with Shore Power. The heater fan came back on and stayed on.

[MudDog]

I believe the furnance has a time relay in order to keep the fan blower blowing for awhile after the thermostat turns off the burner (to dissipate the heat build-up).

If, with the thermostat wires disconnected the fan comes on, but the burner stays off, it sounds like perhaps the relay is stuck. Does the fan come on immediately after re-connecting power?

You could probably try to test the relay with a multi-meter. It's supposed to power the blower when the thermostat calls for heat and then stay on for a time period after the thermostat signals a stop. But if the relay were stuck the fan could keep blowing.

This parts site lists a relay for your model furnance:

www.rvmarineworld.com/camping/pdf/suburban-furnace-parts.pdf

--jim

[Travler]

Originally Posted by MudDog

I believe the furnance has a time relay in order to keep the fan blower blowing for awhile after the thermostat turns off the burner (to dissipate the heat build-up).

If, with the thermostat wires disconnected the fan comes on, but the burner stays off, it sounds like perhaps the relay is stuck. Does the fan come on immediately after re-connecting power?

You could probably try to test the relay with a multi-meter. It's supposed to power the blower when the thermostat calls for heat and then stay on for a time period after the thermostat signals a stop. But if the relay were stuck the fan could keep blowing.

This parts site lists a relay for your model furnance:

www.rvmarineworld.com/camping/pdf/suburban-furnace-parts.pdf

--jim

Yes it comes on when the TM is powered up. I just talked to a dealer he said it could be the control board.....but I do think you may be correct about the relay. Now all I have to do is figure out where the relay is at so I can remove it and test it........any Ideas? Oh BTW Thank you.

[MudDog]

It is probably on the main board - depending on the year/board revision it may be soddered onto the board or it may be a plug-in relay that would be easier to replace.

The parts link had a rough sketch of what it looks like. Compared to everything else on the board, it will be fairly large and will likely be cube shaped and completely enclosed in plastic.

The relay will take input from the thermostat (which could be a 12V or could be a lower voltage) and that input will allow the internal switch in the relay to switch on or off. The internal switch is connecting or disconnecting power to the fan. It's a time relay so that there is a x second delay before the switch shuts power off to the fan.

So you have three connections on the relay:

1 signal connection (in this case from the thermostat)
2 power (12V)
3 output (the fan)

The signal from #1 is allowing #2 and #3 to connect. If that switch is stuck, you get a fan that won't shut off

If the relay is soddered on, it may be easier to replace the whole board.

If it's a plug-in, it should be easy to swap out.

The fan in the NT-20-SE is directly controlled by the control board. The NT-20S is very similar to the NT-20SE, perhaps just a difference in how hot-air is ducted?

[Travler]

Originally Posted by MudDog

It is probably on the main board - depending on the year/board revision it may be soddered onto the board or it may be a plug-in relay that would be easier to replace.

The parts link had a rough sketch of what it looks like. Compared to everything else on the board, it will be fairly large and will likely be cube shaped and completely enclosed in plastic.

The relay will take input from the thermostat (which could be a 12V or could be a lower voltage) and that input will allow the internal switch in the relay to switch on or off. The internal switch is connecting or disconnecting power to the fan. It's a time relay so that there is a x second delay before the switch shuts power off to the fan.

So you have three connections on the relay:

1 signal connection (in this case from the thermostat)
2 power (12V)
3 output (the fan)

The signal from #1 is allowing #2 and #3 to connect. If that switch is stuck, you get a fan that won't shut off

If the relay is soddered on, it may be easier to replace the whole board.

If it's a plug-in, it should be easy to swap out.

On the 2007 2720SD the main board is located in the hall next to the bathroom/Shower......should be easy to find.......hope its a plug in.

[MudDog]

Just to clarify, the board in question should be within the heater itself - it's not part of the converter in the hallway.

Be sure you have all power/batteries (or fuses) disconnected before going anywhere near the wiring/heater circuit board.

Here's a link to a Suburban Furnance Parts manual with perhaps a better picture than the first link:

www.tada-rv.com/scripts/pdfretail/get.php?id=274

Look at the 'Delay Relay' on page 4 to see if you have it on your heater board.