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Lumatic · 03-02-2010, 07:55 AM

I'm looking for troubleshooting advice

Last night my 5 year old NT 30 furnace ran fine until the wee hours of the morning and then stopped heating. The blower kept running. Tried letting it sit and restart. Thermostat OK. Blower starts but furnace does not fire. Gas OK. Outside temp in the upper 20s. Any suggestions where to start?

Thanks,
Marshall

overlander63 · 03-02-2010, 08:12 AM

Check the battery voltage.

david686 · 03-02-2010, 08:29 AM

You might have a bad 'sail switch'. I had same trouble, 'gas level fine, blower starts, but does not light'. The sail switch is just an 'on/off' switch that measures the amount of air flow from the blower. Not enough flow, switch stays off and does not allow the gas to light: Or if switch is broken (like mine) it doesn't turn on and gas will not light. I found out about the sail switch in a recent issue of either "Trailer Life" or "Highways".

Mike Leary · 03-02-2010, 09:51 AM

Given Suburban's reputation as "masters of the cold", I'm suprised your unit has lasted that long. The only thing you can check other than Terry's suggestion without pulling the furnace would be the electrode. If it's the ignitor board, replace it with a "Dinosaur".

Dinosaur Electronics Home. High quality circuit boards for RV appliances.

rickandsandi · 03-02-2010, 11:11 AM

We had the same problem with ours last fall. It is not the voltage because the fan is going on. Might be the paddle switch but have you tried pushing the reset button? We pushed it once and problem gone.

ventport · 03-02-2010, 11:27 AM

If the voltage is low, the fan can run slower then normal with out moving enough air to activate the sail switch, so the burner will not light. Charge the battery first and try the furnace. It's the easiest thing to do so do it first.

richinny · 03-02-2010, 11:34 AM

could moisture in the gas line frozen, blocking gas flow?

Lumatic · 03-02-2010, 01:15 PM

I just disconnected the lead going to the electrode and checked for power with a test light with furnace running. No power to lead. Hooked up to shore power and have 13.3v.

I replaced the electrode about 3 years ago. I did not yet pull it out.

When I fired up the furnace last night I was hooked up to shore power. During the night shore power was turned off. When I found no heat the blower was on batt voltage was at 12.2. In the morning I hooked back up to shore power with no luck.

When the furnace failed I lit a stove burner with no problem. I also switched from a partial LP bottle to a full one.

I assume no power to the electrode points to one of the problems mentioned above. Anything else anybody can think of trying before I pull the furnace?

Any further recommendations on order of troubleshooting, or should I just take the furnace to someone who, hopefully, knows more than I do?

I don't see a reset button. There is a power switch on the furnace I turned off and on again.

Mike Leary · 03-02-2010, 01:37 PM

If the furnace has to come out, you should replace the sail (limit) switch, card and motor; they will all fail, sooner than later. I'd be looking at the gas valve, too. Blow out all the feed lines with compressed air, also. Since misery loves company, I've, since 01, replaced the heater motor three times, the gas valve once, the electrode twice, the ignitor once and the limit switch three times. I think I've got another limit switch gone bad, the furnace will run for a few minutes then go into lockdown.

Lumatic · 03-02-2010, 05:46 PM

Quote:

Originally Posted by Mike Leary

If the furnace has to come out, you should replace the sail (limit) switch, card and motor; they will all fail, sooner than later. I'd be looking at the gas valve, too. Blow out all the feed lines with compressed air, also. Since misery loves company, I've, since 01, replaced the heater motor three times, the gas valve once, the electrode twice, the ignitor once and the limit switch three times. I think I've got another limit switch gone bad, the furnace will run for a few minutes then go into lockdown.

Should I just get a new one? Can you still get them from Palomino? Anyone have the Palomino address.

I went to the local RV guy. He said the igniter wire was high voltage and testing it with a 12v tester will blow up the tester. It didn't, so I guess there was no power. It looks like it has to come out. He is willing to work on it.

Anyone know if a new NT 30 will slide into a 5 year old NT 30 cabinet?

Mike Leary · 03-02-2010, 06:02 PM

Five years sucks; find someone who knows what's going on with that furnace, even though you've read my previous post about how I feel about Suburban products.

Lothlorian · 03-02-2010, 06:28 PM

This is where I bought my suburban furnace last fall. I paid 430.00 plus tax and shipping. LDV

Google Image Result for http://www.ldvusa.com/images/parts/small/22060021.jpg

Lumatic · 03-03-2010, 04:54 AM

If I just buy a new NT30 will the inside components fit into the old cabinet. In other words, I don't want to remove the old cabinet if I don't have to. Can I just slide the new unit in the old NT30 cabinet?

Lothlorian · 03-03-2010, 07:25 AM

Yes, There are several threads with photos on how to do it. It was easy. I followed Pizza chops directions and photos and somebody elses. It took me about 3 hours. If I did it again I bet I could knock it out in 1 hour. It all depends how old your orginal furnace it. Mine was a 70's Suburban furnace. It works great.

Brian

Lumatic · 03-03-2010, 08:10 AM

Quote:

Originally Posted by Mike Leary

If the furnace has to come out, you should replace the sail (limit) switch, card and motor; they will all fail, sooner than later. I'd be looking at the gas valve, too. Blow out all the feed lines with compressed air, also. Since misery loves company, I've, since 01, replaced the heater motor three times, the gas valve once, the electrode twice, the ignitor once and the limit switch three times. I think I've got another limit switch gone bad, the furnace will run for a few minutes then go into lockdown.

Referring to the terms above and other posts:
1. Is the "sail", "paddle" and "limit switch" the same part with different names?
2. Is the "card" and "circuit board" the same part?
3. Is the "electrode" an "igniter" the same part?

Can someone advise me on my laundry list of parts to rebuild the NT 30SP. I'm thinking sail switch, circuit board, motor, electrode at minimum. What would the parts cost? I can get a new NT30SP from Palomino for less than $400 shipping included, so I'm wondering if a rebuild is worth it?

Mike Leary · 03-03-2010, 08:41 AM

Quote:

Originally Posted by Lumatic

Referring to the terms above and other posts:
1. Is the "sail", "paddle" and "limit switch" the same part with different names?
2. Is the "card" and "circuit board" the same part?
3. Is the "electrode" an "igniter" the same part?

Can someone advise me on my laundry list of parts to rebuild the NT 30SP. I'm thinking sail switch, circuit board, motor, electrode at minimum. What would the parts cost? I can get a new NT30SP from Palomino for less than $400 shipping included, so I'm wondering if a rebuild is worth it?

My guys call it a "limit switch", I'm not sure about the other two terms. Questions 2 & 3, the answer is "yes". A new motor is around $130.00, the limit switch is cheap, around $15.00, a gas valve is around $100.00, a card is $100, also. I think I'd buy a fresh furnace, that way you'll have warranty.

Lumatic · 03-03-2010, 09:51 AM

Quote:

Originally Posted by Mike Leary

the limit switch is cheap, around $15.00,

If I am reading my diagram correctly the limit switch is in the front left lower corner of the furnace. If that is what I am looking at it is easily accessible. Do I have that right?

The electrode (igniter?) is also right in front.

I am thinking before I pull the furnace it may be worth dropping a new electrode and limit switch and see if that gets er goin. If I go through the work of pulling the furnace I will just drop a new one in.

Mike Leary · 03-03-2010, 09:55 AM

I can't get to the limit switch in my configuration, but try that if you can get to it; like I said, I've gone through a lot of them. Be sure and replace the gasket on the electrode housing. You don't need to take the entire housing apart, only the center.

Lumatic · 03-03-2010, 01:34 PM

I took the limit switch out and tried to start the furnace, no heat. I connected the limit switch leads with a jumper wire and voila, heat. So I guess it's a bad $15 limit switch and I can postpone the inevitable a little longer.

By the way, you can still get a NT 30 SP from Palomino for $350.