Suburban furnace in Ice Castle - Help?

[Glockwinger]

My Suburban NT-20S heater will not start when I turn on the thermostat.

After a great ice season, I "summer-ized" my Ice Castle and put it away for a few months. On Saturday, I went out and started getting the ice house ready for deer hunting. When I tried to fire up the heater, it did not turn on. I went through the normal checklist: battery connected? Check. Correct polarity to the connection? Check. Gas turned on? Check. Thermostat operating correctly? Check. 12v power at the furnace connection? Check. Plugged vent holes outside? Nope. Does the stove light? Yes.

So...I removed the heater and bench tested it again with 12v. Nothing. I took the heater out of the outer sheet metal sleeve and cleaned it out, removed excess rust, wiped it down, checked all electrical connections, etc. Tried it again...nothing. I then removed the blower motor from the assembly and bench tested that. Worked great! Reinstalled the blower motor and hooked the heater to 12v...nothing.

My best guess is that somehow even though the heater worked great when I put it away, the circuit board has somehow failed. The heater is a Suburban NT-20S. I found a number of RV sites online that carry the circuit board needed for a replacement for around $100. Does anyone have any experience with this type of failure? The circuit board replacement is extremely easy and relatively inexpensive vs. replacing the furnace for $500. I just wondered if anyone had any additional things to try before I purchase the circuit board.

Thoughts from the FM brain trust?

Thank you...

[iffwalleyes]

That seems pretty odd. I the same furnace in my Lodge last trip last year I had a fry pan rattle off the shelf above my heater and land on top of my batteries. It arc across and the only think in the whole house without a inline fuse was my heater. If fried the wiring going into the furnace. I figured for sure it would have done something to the board as well. Took it to a local HVAC place and the replaced the wire that I had fried and that was it and I was back up and running. It kind of seems unlikely that the board would be fried to me especially after what I did to mine didn't do it. Though it seem you have done all the other checks. There is an on off switch on the side of my furnace that hasn't by chance been bumped off accidentally has it. When you were looking at the board you didn't see any burn marks did you again guessing you didn't? If you can find the board for $100 though I would for sure replace that than the whole heater. They are a great little heater.

[Glockwinger]

iffwalleyes,

Thanks for the response. Yup, also tested the switch on the side of the heater. I tried bypassing the switch and there was no change. No burn marks. I think I'm going to try to new circuit board.

[OutlawBiz]

I will make a call over the guys at the Lodge Fish Houses...last year I was having furnace issues was told by one shop that I needed a new circuit board. Guys at the Lodge laughed and said it was HIGHLY unlikely it was the circuit board! I can't remember exactly, but something like the "sail switch" gets dirty / sticky and they shoot a blast of air from a compressor into the exhaust port to clear it or something. Whatever it was worked and was easier / cheaper than the alternative!

Once they open, I'll call or run over there and ask what they did exactly. Maybe it will solve your problem too...stand by...

[OutlawBiz]

After thinking back...my issue was that my furnace would run, it just wouldn't fire / ignite! So, different issue than you are having. Sorry, I didn't read your post closely enough. BUT, if anyone has the same issue I had (not firing, but blower running)...this is one trick the guys at the Lodge said to try:

One of the guys said there is a RESET button / switch on the right side of the furnace unit (as you look at the furnace from inside the shack - it's on the right side). Typically inside a hole that has a rubber grommet around it. It may be hard to physically see depending on how it's placed, but you should be able to feel it if you reach in / around. He said if you ever run out of propane while the furnace is running / in use it can quit firing.

He said you need to:

1) Turn the thermostat OFF, make sure the unit is not running / blowing any air

2) Flip the switch off and on again.

3) Turn thermostat back on and see if it fires

4) If it doesn't work. Turn thermostat off again, wait for the unit to quit blowing / clearing the unit

5) Repeat steps 3 & 4

6) Try not to ever run completely out of propane while its running!

[Glockwinger]

Great! Thanks! I also contacted Suburban directly and they sent me some info. It appears the sail switch is activated after the blower fan starts up. If the blower is not blowing, the switch is not active. I did attempt to bypass the sail switch and the unit still did not start up. That would be a great and cheap fix!

Also, thank you for the clarification of what your heater issue was. I'll look to see if there is a reset on my heater.

[Surface Tension]

Have a read. Suburban NT Operating Manual. Plus, its going to take some time for the air to be purged from the lines.

[harvey lee]

I agree in regards to the sail switch, the fan-blower will start, then the sail switch needs to work. If the sail switch does not work, the furnace will NOT start.

The entire heater works in a sequence and if one does not work, the furnace will not fire.

I would agree with Surface on purging the air out of the line.

A faster way to do that, have the thermo on off and with the gas valve open at the tank, crack open the gas line fitting closet to the furnace until you can hear gas coming out of the line, you will know. Then reconnect and try it again. May have to try it 2-3 times to get it to fire as there could be some air in the furnace yet but you will know you have gas to the unit.

Make sure you get the fitting you loosened up tight again, would not hurt to take some dish soap and wipe it on the fitting you loosened up and make sure there are no bubbles in the soap, sure way to check for leaks.

[Glockwinger]

I agree in regards to the sail switch, the fan-blower will start, then the sail switch needs to work. If the sail switch does not work, the furnace will NOT start.

The entire heater works in a sequence and if one does not work, the furnace will not fire.

Thanks all for the replies. Since the fan blower does not start at all, it cannot activate the sail switch, which does not activate the gas valve or ignition circuit. Still putzing with it...

[Surface Tension]

When you said it doesn't turn on that could have meant a few things.

Blower doesn't start. Since you tested the blower and it works we can assume your not getting voltage to the blower. Check the Tstat. First thing is to look for is a spider web.

Then go onto the following.

A. Thermostat Is Calling For Heat, but The Blower Does Not Run:

1.

Check for 12 volts DC at the furnace connection. Correct power source if "0" volts or

below 12 volts DC.

2.

Check all wiring for correct polarity (refer to wiring diagram), loose connections and

possible shorts.

3.

Check the wall thermostat and wiring for continuity. Be sure thermostat points are

contacting.

4.

With thermostat points closed, check for circuit completion across terminals 2 and 4

of the thermostat relay. If no continuity, and wiring to the relay is okay, replace the

relay.

5.

If there is continuity across terminals 2 and 4, and the wiring to the motor is okay,

replace the motor.

6.On time delay relay

models, allow 3 to 10 seconds for the circuit to be completed to

the motor, as the coil in the time delay relay must heat up to close the contacts

[RiverChuckNorris]

I'm not the sharpest bulb on the tree nor the brightest knife in the drawer and no electrician, but have you tried replacing the thermostat? I had the same issue a couple years back with my IC, went to the Depot and bought the most simple-stupid thermo I could find and presto, it has run like a champ since!

[mmartin]

I had the same problem with mine. The cheap thermostat that they give you sucks. Try crossing the wires and see how that works.

[Hawg]

Not to jump this thread but why do so many IC furnaces have so many problems? I can understand being undersized, that's just IC cutting corners again, but it's always something. It seems we always have a IC furnace thread going.

[Glockwinger]

I'm not the sharpest bulb on the tree nor the brightest knife in the drawer and no electrician, but have you tried replacing the thermostat? I had the same issue a couple years back with my IC, went to the Depot and bought the most simple-stupid thermo I could find and presto, it has run like a champ since!

I disconnected the thermostat and jumpered the wires and still the blower did not run. I ordered the circuit board from an online RV distributor for less than $90 shipped. Thanks for the idea though. Been thinking about changing the thermostat to a different type anyway...

[Glockwinger]

Not to jump this thread but why do so many IC furnaces have so many problems? I can understand being undersized, that's just IC cutting corners again, but it's always something. It seems we always have a IC furnace thread going.

To be fair...the furnaces in question have issues when installed in RV's as well based on the research I did. My guess is the amount of jostling they go through bouncing down the road vs one in your house.

[Glockwinger]

I had the same problem with mine. The cheap thermostat that they give you sucks. Try crossing the wires and see how that works.

I did this, and still did not work. I'll try the new circuit board and keep everyone posted.

[Glockwinger]

This is what the furnace looks like pulled out of its "shell". This is a view of the right side of the heater when looking at it from the front. The top of the heater is toward the bottom of the picture. The front of the heater is at the right side of the picture.

[Surface Tension]

OK you jumped the TStat wires.

Do you go onto the next step?

4.With thermostat points closed, check for circuit completion across terminals 2 and 4

of the thermostat relay. If no continuity, and wiring to the relay is okay, replace the

relay.

[Glockwinger]

Received the new control circuit board in the mail yesterday and installed it in the heater. Hooked it up to power and if fired right up! Cross that problem off my list. Thank you all for the replies and trouble shooting assistance.

Now back to remodeling my booth into a couch thread...

Cheers

[Surface Tension]

Good to hear you got heat.

Did you look at the board for burnt components or a crack.

[Glockwinger]

I did look at the old board. Could not find a crack, burned spot, loose component, melted solder, no burned smell, etc. I am guessing that the relay on the board went bad. Appreciate your insights.

[iffwalleyes]

Glock I got a question. Last year when I had pulled my furnace out and looked at it. All be darn if I could figure out how to get the guts of the furnanace out of the shell short of drilling out all the spot welds. What do you do to get it out. I like to think I am pretty handy with fixing things but this one had me scratching my head and I knew I didn't want to fudge it up. I just took it to and HVAC place and they did not drill anything out so obviously there has to be a trick. A tab to be bent out of the way or something.

[Glockwinger]

iffwalleyes,

I turned the heater over about three times until I figured it out. I found schematics online that showed it removed, so I knew it had to be removable without destroying the sleeve!

After removing the gas line and electrical wires, remove the small 1/2" set screw just below where the hard gas line runs on the bottom of the unit. Then slide the guts out of the sleeve to the front of the sleeve. You can push on the exhaust port to help it. Mine was pretty stuck, so I "helped" it with a rubber mallet while supporting the sleeve. Be careful you don't pinch the wires that are threaded through the plastic grommet.

[iffwalleyes]

I was so close if all I would have to do is use a hammer. I know how to do that. Did everything else.

[smitty1018]

I have a 2014 IC, after only a couple of uses, I had the same problem, I called IC direct, and they admitted to me that they had several problems with the circuit boards, and also the wiring harness. They also said that they had not yet figured out what was causing the problem. After lots of complaining, they replaced my furnace. Maybe worth your time to give them a call. Good Luck!