Suburban NT30: Pilot Light Won't Light

[2xS]

Hello All!

This is my first thread on this forum. I purchased a 71 Airstream Sovereign in early July and have been working on it everyday since. The previous owner assured me all the appliances still worked, and I have no reason to believe the contrary.

I suppose I should have checked all the appliances when I got it; however, there was a wealth of other distractions to keep me busy until heat became mandatory...

A check on full tanks 2 days ago yielded bitter-sweet results: the 10-gallon water heater works great, and the stove works great; the oven constant pilot will light, but the oven burner fails; and the furnace pilot shows no signs or lighting.

I have followed all the operating instructions attached below without success, and I posted pictures. I also read through the forums to see if something there would help. The solution always seemed to be to replace it, but I am hoping that is not the case. I suppose I am hoping that I missed some trick that will get the pilot lit without the ordeal of attempting to repair or replace...

Any suggestions are greatly appreciated!

[HowieE]

Your second picture shows a gas valve in the off position. If that is the gas valve for the furnace make sure it is turned on and then crack the flare nut just past the valve until you smell gas. Tighten the nut and try again.

Often when the tanks have been removed from the trailer air will get into the lines. The pilot orifice is so small it will not bleed the line and thus you think the heater is not working. By purging the line at the flare nut you stand a chance.

Not saying that is it for sure but you will at least know gas is at the heater before you go any further.

[LLB21]

Sometimes it is hard to see things. Try lighting the stove first and get the gas flowing good and work your way back to the furnace.

[2xS]

SUCCESS!!! (At least for the pilot...)

There was only 1 of 2 things I could've possibly done to remedy the pilot:
1) I blew (by mouth) directly on the pilot opening inside the hole cover, or
2) I posted a thread on this forum...

Either way, I just fired up the gas and tried again; it lit on the second match.

BUT now there is a new problem, as I can't get the furnace to heat or blow. I'm going to have to assume the problem lies with the thermostat as it says it's currently 85 in the trailer while my pipes are frozen; I had also disconnected the thermostat while renovating. There were 2 blue wires connected to a Honeywell thermostat, and of course, I didn't mark them before disconnecting. I tested the line and I get a clean +12V across the wires. I'd like to assume that it wouldn't matter what wire I connect to each terminal; however, I know that isn't usually the case with a DC system.

I had planned on replacing both the A/C thermostat and the heater thermostat into one Carrier universal touchscreen thermostat, and I have ran a wire to do so.

So I guess my questions now are:

Is there any reason replacing the thermostat won't solve the problem?

Are the thermostat connections polarity sensitive?

Is there a way to bypass the thermostat (SAFELY!) and run the furnace while I wait for my thermostat to come in the mail?

Any comments/suggestions/advice???

[arodriguez60]

Here is an owners manual with a wiring diagram http://www.nwrvsupply.com/manuals/su...on_service.pdf

[68 TWind]

Just a thought. Your furnace is nearly 40 years old. If it is not working properly it would be money well spent to have someone who knows what they are doing with RV heaters check it out. I had a NT=22 in my Trade Wind and I was working "most" of the time but I thought I'd let a buddy in the HVAC business check it. I pulled the furnace out of the case, took a propane bottle and a battery to his shop. While checking, He found a hole in the heat exchanger (not the crossover as that had be retrofitted). That could have been deadly. Just my two cents worth, but at the very least have a CO detector in your trailer.

[2xS]

Thanks everyone for the responses!

I would like to report a COMPLETE SUCCESS!

I couldn't stand it anymore, and instead of waiting for my touchscreen thermostat in the mail, I went to Wal-Mart and bought this airforum recommended Hunter; I picked up the "Set & $ave" 5-2 day programmable model: $20.

Came back and had it hooked up in 2 minutes (would've had it in 30 seconds if it wasn't so cold!) and VIOLA! Heat!!! Oh glorious heat!

My only complaint is that odor you get when you use some heater/furnace for the first time of year; I don't smell any propane but I have a vent and exhaust fan running nevertheless and I will continue to until I can verify that there are no gas fumes leaking anywhere.

SUCCESS RECAP:

Problem:
A) Pilot light didn't light.
Answer:
1) Light every other appliance.
2) Blow (by mouth) directly on pilot.
3) Follow furnace startup procedure.

Problem:
B) Furnace and blower failed to engage.
Condition: Thermostat temperature reading incredibly wrong
Solution:
1) Go buy a new battery operated thermostat; this test used the Hunter "Set & $ave"
2) Hook it up. (wire/terminal connections are polarity insensitive)
3) Be happy and warm... maybe make yourself a drink... hey, you earned it!


Cheers!

[2xS]

UPDATE:

The furnace works great; however, there is a burning plastic smell that emanates from... somewhere. I'm going to assume it is coming from the disgustingness on the side of the furnace (shown in the bottom right picture of the first post) as my eyes tend to really start watering up if I stick my head near there. I killed the furnace for the night, and I plan on throughly cleaning that area tomorrow, and running the furnace with doors wide open all day. I'm hoping that if cleaning the site of the suspected area doesn't work, that I could possibly burn off whatever is causing the burning smell withing the chamber (if indeed there is something foreign in there).

Has anyone else encountered this?

Am I on the right track?

Have I mentioned this is my new favorite website?

[2xS]

How quickly success turns to failure...

Everything goes fine, and then about 2 minutes with it on, there is a click (coming from the furnace) and then the fan blows cold air. A quick glance under the lighter cap reveals the pilot extinguished. The only advice owners manual suggests that if the fan and the burner goes out 2-3 minutes into the cycle, then the cause is a shorted fan switch (which could explain the plastic burning smell) except the fans continue to operate.

Not cool... in fact, cold... :'(

[garry]

The furnace is kind of funky when it comes to voltage the fan must turn at 75% of full speed or it will shut down. The air volume is monitored by a sail switch (micro switch) with a blade (sail) attached. The click could be the sail switch shutting down the gas valve.
The motor could be slowing down as it heats up from old age. Kind of like me.

You might give the 12V connections a check at the furnace with the fan running there could be some corrosion creating enough resistance to slow the fan down.
Of course it could be the limit sw you could jumper around it as a test and also the radiators being covered can cause an overheat condition by not enough airflow.

One other thing there was a safety recall on the furnace due to the crossover from the heat exchanger getting brittle and collapsing allow CO into the camper.

The only way I know to check it is to pull the furnace I replaced mine with a radiator hose from NAPA easy job and it will give you the opportunity to give everything a once over should yours be bad.

If the pilot light flame is not hitting the thermocouple full on the pilot can shut down when the furnace is running from air motion.

Lot of rambling here but I hope it gives you a few things to think about.

[BossCamper]

Originally Posted by garry

If the pilot light flame is not hitting the thermocouple full on the pilot can shut down when the furnace is running from air motion.

I had my furnace going out like that. One of the main things was that the pilot was partially clogged, resulting in a weak pilot flame. Maybe yours could stand a cleaning.

Andy from Inland RV had a good suggestion for cleaning it here

http://www.airforums.com/forums/f427...jet-58910.html

[2xS]

I have just discovered this horrifying possibility... After reading through threads on this site I found a familiar post by Lumatic in Jan 2007,

"The main fired for a minute or so, THEN I HEARD A DISTINCT CLICK I didn't notice before and the burner and pilot were both out. The fan kept running until I shut it off with the thermostat 5 minutes later. I will try it again when it warms up outside a little more. Also, there is a DISTINCT SMELL that I don't think should be there when the burner fires and the furnace is warming up. Maybe it is just that this furnace has not been used for many years, or, COULD IT BE SOME KIND OF BREAK DOWN IN THE COMBUSTION CHAMBER SEAL from the heat exchanger?"

Lumatic goes on to find nearly all models of Suburban furnaces manufactured between 1966-1977 were recalled due to faulty rubber crossover tube that would cause carbon monoxide to expel into the cabin.
Suburban furnace

Fantastic... My victory and success for a time was actually poisoning me with CO while I laughed and danced about.

I'm not sure where to look for the serial number, but every other thread on this issue now suggests the only way is to remove the heater to even check to see if there is a rubber heat exchanger hose connected to the unit; I'm also going to assume the serial number is somewhere back there too.

Given the situation, I believe I will use the old fashion whiskey heating method, and begin looking for a replacement...

[HowieE]

If you now have the pilot light lighting and after a few mins. the main gas shuts down I would think that is because the main flame is pulling the pilot flame away from the thermocouple. If this is happening the thermocouple would shut off the main gas, THE CLICK, you hear is the gas valve closing.

To check this remove a wire from the gas valve selenoid, most valves have a 2 chambered gas valve. Lifting one of the wires off the gas valve selenoids will keep it from opening once the thermocouple has proved flame. Light the pilot and let it burn for several mins. more than what you have seen with the flame shutting down. Now connect the wire, main flame should light, and see if the flame goes out in a short period of time.

If the flame fails after reconnecting the wire the flame is most likely pulling the pilot flame away from the thermocouple and causing shut down.

If this happens take another look at the pilot flame and how it impinges on the thermocouple. If the flame is misshapened, dirty orifice, or off center to the thermocouple correct that and try again.

[garry]

Originally Posted by garry

One other thing there was a safety recall on the furnace due to the crossover from the heat exchanger getting brittle and collapsing allow CO into the camper.
To check it pull the furnace I replaced mine with a radiator hose from NAPA easy job and it will give you the opportunity to give everything a once over.
.

From my earlier post I did this 4 years ago and it works just fine however we seldom use the furnace, less expensive than a new furnace but the new ones with no pilot light sure are convenient.

[2xS]

Thank you guys for your input!!! I love this site!!!

I want sooo bad for one of Howie's or Gary's suggestions to remedy the problem WITHOUT having to remove the furnace (I have 1,000 other projects going). I decided to just go ahead and assume the worst. But after reading through posts here again, I decided to take a few pictures before I got started... with the pilot on. While trying to get a decent shot of the pilot with a digital camera (pretty ridiculous), I decided to fire it up. The furnace and fan came on just as expected, and the horrible plastic burning smell wafted through the trailer. Still prepared for the worse, I waited for the audible click again, but it never came. After about 5 minutes, it was still blowing warm. I turned the thermostat off, and checked the pilot. It was still going. I kicked it back on, and it just keeps going...

But there is still the wretched burning smell coming from the vents not to mention a white smoke that comes out of the exhaust vent on the outside. I have all kinds of ventilation going on while it's been running, but it should most likely not be running. The inevitable and horrible fact is: no matter if it works or not, I have reason to believe that my furnace was manufactured during the great Suburban furnace recall of 1966-1977 and is victim to such recall. I am sure the furnace has never been pulled out. According to 'Step 2' of the instructions, a 3" hole would need to be cut out in the shelf above (hole saw in there, how?) in order to unlatch the furnace front panel. You can see what I see; no such hole exists. QUESTION: What sick ____ installed this furnace? Another point, I'm not happy with Suburban right now, and what do most people replace their Suburban with? Another Suburban... This whole thing is just kinda getting to me... probably because it's my own fault I didn't check it sooner, and now there's a sense of urgency because it's freezing. And those tambour doors... thery're so fussy; I don't see how I'll be able to pull it out without removing that lower rail. Disassembling the kitchen counter was NOT on the 'to-do' list.

Time to suck it up, and do what needs to be done.

[2xS]

bahh...
wrong instruction attachment..

[garry]

Well you could have a Mud Dabbers or Hornets nest in the exhaust/intake pipe and around the fan, most units do, I'm not sure if that would cause a smell inside.
How about dead mice??

Sounds to me like you will have to remove the furnace but you do not have to make a decision to replace until after you have checked it out.

My furnace was not that hard to remove. If I remember the 2 screws in the front the gas lines, DC wires and the screws on the outside were about it. I'm sure I would remember having to drill holes but it may have been pulled by the PO.
It is ALWAYS easer to R&R the next time.

When reinstalling step #11 is important for the exhaust and intake pipes line up at the outside holes and you will have to have the gasket material that goes around the intake/exhaust holes even if replacing with a new unit. The gasket material will probably be brittle and not reusable. Seems like I bought mine at Ace Hardware.

Also if replacing you have to have a compatible replacement. Some of the newer units are physically smaller and will line up with the outside holes. but a lot of the models will not.

Now for the last part when you tested the furnace did you have the access door open? If yes try it again with the door closed.

Garry

[Lumatic]

Another consideration for this vintage furnace is finding parts or someone willing to work on them. Been there done that.

[2xS]

It's out.

That wasn't nearly as horrible as I thought it would be... My only issue was that I had to partially drill out the screws holding the intake plate, because they were stripped out pretty bad.

Gary: It's like you're psychic. I opened the vent cover and BAM! Blackened hornets and a nest that didn't look so pretty. Thanks for the info about the replacement gasket too... The old one is toast.

The serial number is located under the clip-off front panel on the right, can't miss it. Although you do have to drill holes in your galley to make it that far. My serial happened to be 0104047 which falls fairly early within the range of recalled models. This led me to believe I was on the right track. Once I got the furnace out, there was a severed rubber hose, plain as day.

Now I get to decide:
Should I try to repair it?
Or should I be cheap this Christmas and buy myself a new furnace?

It seems like it might be a good time/idea to retire it... but then again it seems in fairly decent shape for its' age.

[garry]

Well for me it was a clean it up, go to NAPA for a radiator hose and reinstall, figured I would replace it later.
That was 4 years ago I just don't use it that often and it does work just fine should

I ever have to remove it again I probably would replace it I like the idea you turn the thermostat on and it lights no pilot light to mess with.