Home » Public Forums » GMCnet » Suburban Furnace NT 30. Irradic ignition (Thinking limit swich.)
| Suburban Furnace NT 30. Irradic ignition [message #268003] |
Mon, 22 December 2014 06:52  |
77Royale
Messages: 461
Registered: June 2014
Location: Mid Michigan
Karma: 6
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Senior Member |
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Greetings. I have been using the furnace in my 77 Royale off and on for the last few weeks. Sububan NT 30M. Serial Number 0802246
I removed it when I got the coach, cleaned the burner, blew air through everything and generally cleaned it up, replaced the burner access gaskets, cleaned all the contacts on the control board with a rubber eraser. It has worked fine up until a few days ago. Temps here are in the mid 30s.
I have a full propane tank, and have purged the air by turning the stove burners on. Those work fine.
I have power plugged into Shore.
All 4 ducts are in place and nothing is clogged in either the intake or exhaust tubes.
The blower motor turns on and runs without issue.
When I first come out to the coach and turn the t stat up, the furnace lights up first try, and burns a nice blue flame for proably 30 seconds or so. Then shuts off. I think I hear a very faint "click". It will not re light until it is cooled down.
When it does not want to re light, I can hear the fan blowing and see through the window that there is an arc across the electrodes. So I think the sail switch is not the culprit as my understanding is if the sail switch is faulty or sticking you will not get a spark in an attempt to light.
When the unit is cold, I can shut it off and turn it back on with ignition as many times as I want without issue as long is it does not get too hot. Its just once it burns and gets warm it will go out and not want to light again until completely cool.
Wondering what the consensus here is? Im thinking a bad limit switch?
I have not meter tested any electronics as its kind of a tight space. Just wondering since it will light just fine and burn for a while that it may be a limit switch.
Thanks for the input.
77 Royale, Rear Dry Bath. 403, 3.55 Final Drive, Lenzi goodies, Patterson carb and dizzy.
Mid Michigan
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| Re: [GMCnet] Suburban Furnace NT 30. Irradic ignition [message #268016 is a reply to message #268003] |
Mon, 22 December 2014 09:42  |
powerjon
Messages: 2446
Registered: January 2004
Karma: 5
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Senior Member |
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Wayne,
There is a high temp limit switch in the control circuit. It is a normally closed (NC) switch which will open at a specified temperature. It sound like that is your problem.
Have you downloaded any furnace manuals?
This one gives a real good explanation on how the furnaces works.
http://www.bdub.net/manuals/Suburban_Tech.pdf
And this one should cover your furnace.
or
http://tinyurl.com/nrf2zju
As for getting replacement parts, most rv stores in your area ( where in MI are located at? ) can get or supply the correct. Or you can go online and order.
Or other parts listed in this section that you may need.
http://www.bigdiscountrv.com/heating-and-cooling/furnaces/suburban-furnace-parts
Good luck!
JR Wright
78 Buskirk Stretch
75 Avion
Michigan
> On Dec 22, 2014, at 7:52 AM, Wayne Rogewski wrote:
>
> Greetings. I have been using the furnace in my 77 Royale off and on for the last few weeks. Sububan NT 30M. Serial Number 0802246
>
> I removed it when I got the coach, cleaned the burner, blew air through everything and generally cleaned it up, replaced the burner access gaskets,
> cleaned all the contacts on the control board with a rubber eraser. It has worked fine up until a few days ago. Temps here are in the mid 30s.
>
> I have a full propane tank, and have purged the air by turning the stove burners on. Those work fine.
> I have power plugged into Shore.
> All 4 ducts are in place and nothing is clogged in either the intake or exhaust tubes.
> The blower motor turns on and runs without issue.
>
> When I first come out to the coach and turn the t stat up, the furnace lights up first try, and burns a nice blue flame for proably 30 seconds or so.
> Then shuts off. I think I hear a very faint "click". It will not re light until it is cooled down.
> When it does not want to re light, I can hear the fan blowing and see through the window that there is an arc across the electrodes. So I think the
> sail switch is not the culprit as my understanding is if the sail switch is faulty or sticking you will not get a spark in an attempt to light.
>
> When the unit is cold, I can shut it off and turn it back on with ignition as many times as I want without issue as long is it does not get too hot.
> Its just once it burns and gets warm it will go out and not want to light again until completely cool.
>
> Wondering what the consensus here is? Im thinking a bad limit switch?
>
> I have not meter tested any electronics as its kind of a tight space. Just wondering since it will light just fine and burn for a while that it may
> be a limit switch.
>
> Thanks for the input.
> --
> 77 Royale
> Mid Michigan
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
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| Re: Suburban Furnace NT 30. Irradic ignition [message #268027 is a reply to message #268003] |
Mon, 22 December 2014 12:02 |
77Royale
Messages: 461
Registered: June 2014
Location: Mid Michigan
Karma: 6
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Senior Member |
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Capital area (Lansing) John,
No one local has one. Kitsmiller can get one by tomorrow. That will give me a chance to pull the old and compare before I leave.
22 bucks, which is pretty close to what I would get online with shipping.
Im assuming the limit switch and "hi temp limit switch" are the same part, Just a different terminology.
I did download a few manuals a while back, Thank you for sharing the links.
I will post back if that is the culprit.
77 Royale, Rear Dry Bath. 403, 3.55 Final Drive, Lenzi goodies, Patterson carb and dizzy.
Mid Michigan
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| Re: [GMCnet] Suburban Furnace NT 30. Irradic ignition [message #268028 is a reply to message #268016] |
Mon, 22 December 2014 12:13 |
Terrance Boyd
Messages: 38
Registered: October 2008
Karma: 0
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I have had a Suburban NT30 furnace in my coach for about 20 years. After
about 15 years it started acting strangely. It would fire, come up to
temp., the thermostat would shut it down. When the thermostat would call
for more heat the blower would run, but ignition would not happen. If I
didn't shut it down manually the blower would have run until the batteries
were dead. It would repeat this most of the time, working sometimes and
sometimes not.
I replaced the sail switch, the control board, high temperature limit,
and igniter, none of these replaced parts cured the problem. They seemed
to help but not cure. I would hear two clicks, in rapid succession, when
the furnace would start, one click when it shut down.
As it turned out, one of the solenoids on the double gas valve was bad.
Evidently it would operate both solenoids cold but only one when hot. Since
I replaced the gas valve, it works like it should.
Just what happened to me.
Good luck
Terry
On Dec 22, 2014 7:42 AM, "John Wright" wrote:
> Wayne,
> There is a high temp limit switch in the control circuit. It is a
> normally closed (NC) switch which will open at a specified temperature. It
> sound like that is your problem.
>
> Have you downloaded any furnace manuals?
>
> This one gives a real good explanation on how the furnaces works.
>
> http://www.bdub.net/manuals/Suburban_Tech.pdf
>
> And this one should cover your furnace.
>
> http://www.bdub.net/manuals/Suburban%20NT%2022A%2022C%2022CD%2032A%2032C%2032CD%20DTM%204-76.pdf
>>
> or
> http://tinyurl.com/nrf2zju
>
> As for getting replacement parts, most rv stores in your area ( where in
> MI are located at? ) can get or supply the correct. Or you can go online
> and order.
>
> http://www.bigdiscountrv.com/heating-and-cooling/furnaces/suburban-furnace-parts/231244-limit-switch
>>
>
> Or other parts listed in this section that you may need.
>
>
> http://www.bigdiscountrv.com/heating-and-cooling/furnaces/suburban-furnace-parts
>
> Good luck!
>
> JR Wright
> 78 Buskirk Stretch
> 75 Avion
> Michigan
>
>> On Dec 22, 2014, at 7:52 AM, Wayne Rogewski wrote:
>>
>> Greetings. I have been using the furnace in my 77 Royale off and on for
> the last few weeks. Sububan NT 30M. Serial Number 0802246
>>
>> I removed it when I got the coach, cleaned the burner, blew air through
> everything and generally cleaned it up, replaced the burner access gaskets,
>> cleaned all the contacts on the control board with a rubber eraser.
> It has worked fine up until a few days ago. Temps here are in the mid 30s.
>>
>> I have a full propane tank, and have purged the air by turning the
> stove burners on. Those work fine.
>> I have power plugged into Shore.
>> All 4 ducts are in place and nothing is clogged in either the intake or
> exhaust tubes.
>> The blower motor turns on and runs without issue.
>>
>> When I first come out to the coach and turn the t stat up, the furnace
> lights up first try, and burns a nice blue flame for proably 30 seconds or
> so.
>> Then shuts off. I think I hear a very faint "click". It will not re
> light until it is cooled down.
>> When it does not want to re light, I can hear the fan blowing and see
> through the window that there is an arc across the electrodes. So I think
> the
>> sail switch is not the culprit as my understanding is if the sail switch
> is faulty or sticking you will not get a spark in an attempt to light.
>>
>> When the unit is cold, I can shut it off and turn it back on with
> ignition as many times as I want without issue as long is it does not get
> too hot.
>> Its just once it burns and gets warm it will go out and not want to
> light again until completely cool.
>>
>> Wondering what the consensus here is? Im thinking a bad limit switch?
>>
>> I have not meter tested any electronics as its kind of a tight space.
> Just wondering since it will light just fine and burn for a while that it
> may
>> be a limit switch.
>>
>> Thanks for the input.
>> --
>> 77 Royale
>> Mid Michigan
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: Suburban Furnace NT 30. Irradic ignition [message #268057 is a reply to message #268003] |
Mon, 22 December 2014 21:24 |
Steve
Messages: 506
Registered: September 2013
Location: East Greenville, Pa
Karma: 1
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Senior Member |
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I also experienced intermittent lighting that I believe was gas valve related based on my troubleshooting from the manual and the good folks from here on the gmc net. I found that tapping on the supply line would open the valve. I am not sure if it was a poor electrical condition to the valve or an actual sticky gas valve. I had trouble year one but after frequent use it became dependable. Now year two I had trouble again but seems to work great after cleaning the connections to the board and gas valve.
Like many other areas of the coach, keep those connections clean and voltages up.
1978 GMC Royal
Eastern Pennslyvania
1968 Chevrolet C20 396 Camper Special
1969 Chevrolet C20 Camper Special
1985 Buick Electra Park Avenue
1992 Camaro 25th Anniversary Heretage Edition Black
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| Re: Suburban Furnace NT 30. Irradic ignition [message #268067 is a reply to message #268003] |
Mon, 22 December 2014 23:05 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Senior Member |
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Sounds like the limit switch to me . Check it with an ohmmeter when the unit shuts off . If it reads o it's not the switch if it shows infinite the switch is open. The switch should have a number on it like L135 which is the temperature the switch opens. If the heat exchanger is at the same temperature you are not moving enough air across it. If the heat exchanger is a number of degrees colder the switch is bad.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: Suburban Furnace NT 30. Irradic ignition (FIXED) [message #268096 is a reply to message #268003] |
Tue, 23 December 2014 11:22 |
77Royale
Messages: 461
Registered: June 2014
Location: Mid Michigan
Karma: 6
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Senior Member |
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Thanks to everyone for the suggestions.
I picked up a new limit switch today and I have sustained ignition!! I also got a set of decent exploded view drawings and part numbers from the RV dealer.
Fired up first try and has been running for 15 mins now. Warming up the coach very well.
For those interested, This was a Suburban NT 30M.
The limit switch part number is 230496. 20 bucks or so sourced locally at an RV place. I dont know if my old switch was ever replaced but the stampings on the back were the same.
Merry Christmas.
77 Royale, Rear Dry Bath. 403, 3.55 Final Drive, Lenzi goodies, Patterson carb and dizzy.
Mid Michigan
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| Re: [GMCnet] Suburban Furnace NT 30. Irradic ignition (FIXED) [message #269060 is a reply to message #268123] |
Tue, 06 January 2015 20:27 |
77Royale
Messages: 461
Registered: June 2014
Location: Mid Michigan
Karma: 6
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Senior Member |
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Sorry, Yes I have a few scans of the print outs.
Erf Can you PM me here and I will email them to you to post up? 3 pages JUST for the NT30M its the combustion chamber assembly breadown. 40 or so parts with current or proper part numbers.
Thanks
77 Royale, Rear Dry Bath. 403, 3.55 Final Drive, Lenzi goodies, Patterson carb and dizzy.
Mid Michigan
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