Suburban Heater...What am I missing??? - Fiberglass RV


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Old 12-29-2008, 06:51 PM   #1
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So I've actually never had the heater running on my own. Before (when i first got the '87 Scamp), I was able to get the blower to run but never actually turned on the heater. I was able to get the blower to run another time but couldn't get the heater to turn on. Last week i took it to an RV dealer and they were able to get the blower & heater to fire up (so they said). They said that the wires were reversed and the blower was running in reverse therefore the heater would not fire up. When I picked up the Scamp my baby was sleeping and didn't take the time for a "full instructional lesson". Tonight when I got home from work I replaced the valve regulator that was near the propane tank, knew that was bad also. However, I cannot get the blower to fire up at all!!! Which means I cannot get the heater going. What am I missing? I'm following the directions as listed in the document found on this site.

It is around 25/30 degrees out this evening when trying to get it to work. Does that make a difference?

Yeah I know I can run electric heat from a little heater, but I really want to get the propane heater to work.

thanks for your help,
-steve
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Old 12-29-2008, 07:23 PM   #2
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heres a site with some owners manual....hope this helps.. scroll down to
Suburban SW water heaters....
http://bryantrv.com/owners.html

Is there a fuse you might check? Sorry I dont know to much about fixing stuff...
I had a whole new water heater, and controls put in last yr, regulators and hoses...

I see your in Minn.. ... you could call Bacus where Scamps are made.. but i am sure someone on the board will help you..
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Old 12-29-2008, 09:39 PM   #3
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Dear Steve,

I am a service tech, the NT series suburban is the one you have I think...The thermostat will call for heat sending +12v to a thermal time delay relay, in 3 min to 5 min depending on how cold you are on first start up the blower will come on when the relay activates, it needs that much time to cycle at first, its using a little 12v heater element built within the switch to heat up a bi metal contact, once it is allowed the time the blower should come on next if you have power and are calling from the thermostat for heat...if It does not cycle then question the screw connections behind the thermostat itself, "unscrew it off the wall flipping it over" the screws are brass or aluminum in the back that year and both oxidize, not allowing a good electrical connection. I would move the wires so they are together to any one screw ruling out the thermostat as a source of the problem right now, measure the continuity at the furnace of this pair of wires to rule out broken wires to the furnace from the T.S.A.T "thermostat".

Once you have proven the wires are good and the t.s.a.t. is bypassed and it still fails to do anything then make sure you have +12v and -12v present to the furnace connector. (it will have four wires, +12v,-12v, +12v tsat source, and tsat return +12v) a cheap 12v auto tester works well. On the fuse question, there is not in the 86 model year control board a fuse, unless the control board was replaced with a new one, if so, the fuse is located on the new style board as an auto type spade 5 amp fuse...it cannot be reached without disassembling the furnace. The most probable problem once +12v and -12v is proven to be present at the furnace and connected with the thermostat bypassed is the T.D.R. "time delay relay" connections.

These spade connections are notorious for oxidizing and failing, with out this component working properly it will act dead, dead, dead. This relay is the beginning of the start sequence of events, unless the blower motor is stuck mechanically by some circumstance unknown (mud wasps are good for this) The T.D.R. is almost 95% of the problem with your symptoms.

I have included a pic of the T.D.R. At this point you must disassemble the furnace.

The component is hidden behind the control board a bit back near the blower motor accessible from the control board side of the furnace. Please F.Y.I. me the exact model number or a pic back to establish in my mind the model you are trouble shooting. The furnace should be a chassis within a sleeve design, "the guts slide into the cabinet from the front".

Its a simple design, if you have a basic average mechanical skill and are on the model I suspect its straight forward...just thumping it after 5 min after the thermostat calls for heat often wakes it alive with this issue.

I include the T.D.R. pic

Harry
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Old 12-30-2008, 08:07 PM   #4
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So I flipped the switch to "ON", moved it to the right and set the thermostat to 60degrees. I waited, and waited for like 10mins for the blower to kick in. Nothing happened. The temp outside is around 20 this morning when I did this.

Last week the "experts" had the said they heater going so it sure seems the connections would still be good, if it was working last week. I thought about putting an electric oil heater and warming everything up a bit to see if that would help. I've only had little bits of time here and there to work on it. Was hoping to take a "winter trip" and do some xc skiing somewhere using the scamp. I can still do this if I go to a state park and have electric, but it sure would be nice to know the propane heater is working also.
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Old 12-30-2008, 11:45 PM   #5
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Quote:
"So I flipped the switch to "ON", moved it to the right and set the thermostat to 60degrees. I waited, and waited for like 10mins for the blower to kick in. Nothing happened. The temp outside is around 20 this morning when I did this."

[b]I understand, its frustrating, if you still would like some help I am willing.

"Last week the "experts" had the said they heater going so it sure seems the connections would still be good, if it was working last week."

(note)** these guys learned these furnaces just like you are...I would hope in a dozen or so jobs they would get it down pat...however, some learning curves are longer than others.

[b]The assumption there is power because there was last week is probable but does not tell me there is 100% Being a tech or trouble shooting is not abouty knowing the magic answer so much as it is a method of investigation knowing how the equipment works. I start with the simple questions like is the thermostat calling for heat? Is there power? then work up to the more technical issues like since the T.D.R is the first thing that must happen why isn't it happening?

If there is power and after 3 min you do not hear a small click with your ear down on the unit the T.D.R. is not cycling...these die two ways usually I have seen in 23 years.

80% 1. It is o.k but for some reason not got power to run it.

75% 2. The #14 a.w.g electrical spade connectors (4 of them) corrode over the years, or loosen up breaking electrical contact...a sign of this is the furnace problems are intermittent often changing with temps seasonally.

60% The Time delay relay has failed.

The solution is to slip the chassis out of the outer sleeve and manually trouble shoot the connections. If you want to do this I will photo on my bench the take apart and the reassemble of an NT series here.

I cannot stress enough the need to establish without a doubt you have good 12v both positive and negative.

Do not assume its correct. I have chased complicated reasons for hours to find out it came down to the simple causes.

To rule out some things you must be thinking about I mention the following.

(1) Gas at this point makes no difference to the start cycle at this point of operation.

(2) The computer is not turned on until the T.D.R. cycles first so it is ruled out or its fuse. "if board is new style"

(3) The sail switch is not the problem as the T.D.R. supplies power to it too and the blower is dead.

(4) A bad motor would not cause your problem because its power comes also first from the T.D.R.

If I were going to pick a problem I would want if my furnace had to break down your problem is the one I would chose... This problem is fixable and cheap to fix too.

If you do not feel you want to go further that's fine, the fix is likely the T.D.R. or its wiring connections, the part is under 30.00 if it were the relay unit itself...The labor rate is more. If serviced have the connections on the wires to the relay replaced anyway "I use nickle connectors" being sure to use an emery board clean the spade connections sticking up at the top of the relay, then reinstall connectors with an anti-oxidant cream available from HomeDepot...I have had a 1995 and a 1990 Scamp in the shop with these issues this fall because its common. About every 10 years it seems the brass or aluminum (depending which relay you got) at the top of this relay oxidizes just enough to lose electrical connections by just sitting there.


"I thought about putting an electric oil heater and warming everything up a bit to see if that would help."

[b]It should not make a difference, I have seen these little guys work when warm and fail when cold because the oxidised connections re-establish themslves due to thermal expansion and contraction of their metals, it never fixes the problem, but it has happened, and always leads me into the unit to clean those connections up.

"I've only had little bits of time here and there to work on it. Was hoping to take a "winter trip" and do some xc skiing somewhere using the scamp. I can still do this if I go to a state park and have electric, but it sure would be nice to know the propane heater is working also."

[b]I would go have fun and take it apart when the climate was more agreeable.

Sounds like you need some fun.

Happy trails from Arizona.

P.S. Please let these boards know what was the solution to your ghost in the machine was when it finally becomes known, I would love to know as well...it helps us all and builds a data base others can draw from, thanks for posting!

Harry[b]
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Old 12-31-2008, 04:36 PM   #6
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Harry, thanks for the encouragement. And I'll keep learning so I can understand and know how to fix it in the future. Yes, the model I have is a NT. Actual model No. = NT 12SE, Code No. = BKX, Serial No. = 002011412.

I did warm it up inside today w/ the electric oil heater. It is nice to know that it will warm up and I can take it w/ me to a state park and enjoy the winter weather.

If I am understanding you correctly, the fuses are located at the back of the furnace. That being the case I need to pull out the furnace to get to them? Am I also correct that it will just slip out with a tug from the front?

I'm not in a huge hurry to get it going, just thought I would begin working on the project b/c it is something that has been hanging over my head to get done.

Have a great New years!!!
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Old 12-31-2008, 11:30 PM   #7
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Test the wires you have for 12v first if good then proceed, if this one has the fuse its on the board the fuse is hidden inside mounted on the control board itself, many of these older NT furnaces do not have a fuse...Anyway with the symptoms you describe I would bet a beer on no fuse problem here...Its the 12v supply or the T.D.R. relay or its wires in my mind.

To get to the works inside an NT series furnace, first turn off the gas at the propane tank, disconnect 3/8 flare nut to the gas line outside of the chassis of the furnace, also all electrical wires (make notes where they go, there are 4) pull the two screws in the front cover, the cover will come off, remove anchor screws on bottom or sides of chassis behind the cover you just took off, slide unit out of cabinet, wiggle left and right a little while removing to ease exhaust/air intake sleeves apart, bench it on a clean work space.* See note.

Note* These furnaces are often located in a cabinetry, taking apart the bench seat in some scamps is necessary...access to the outside of the cabinet is necessary first.

On the bench...

Remove the gas shut off valve screwed into the unit at the side through the outer cabinet shell. Inside the front on the unit right side bottom is a screw with a nut on it "opposite the little window" remove this...tuck the wires into the furnace out of the way inside electrical compartment so they are not damaged when you slide the inside section out of the outside cabinet...its stuffed like a sausage or a glove its that type of fit. Taken apart this way the unit can be repaired and tested on the bench completely.

Feel free to contact me if needed. I will check with Donna D to see if the resource center has manual to this series, if not I will send it to the site.

Harry

Happy New Years 2009

Quote:
Harry, thanks for the encouragement. And I'll keep learning so I can understand and know how to fix it in the future. Yes, the model I have is a NT. Actual model No. = NT 12SE, Code No. = BKX, Serial No. = 002011412.

I did warm it up inside today w/ the electric oil heater. It is nice to know that it will warm up and I can take it w/ me to a state park and enjoy the winter weather.

If I am understanding you correctly, the fuses are located at the back of the furnace. That being the case I need to pull out the furnace to get to them? Am I also correct that it will just slip out with a tug from the front?

I'm not in a huge hurry to get it going, just thought I would begin working on the project b/c it is something that has been hanging over my head to get done.

Have a great New years!!!
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Old 01-01-2009, 01:48 AM   #8
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Wow, Harry, this almost makes me want to run out and get a Suburban NT furnace, just because you've posted this great trouble-shooting guide. It must have taken you a while to type it all out. What a resource this group is!


Raya
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Old 01-01-2009, 09:51 AM   #9
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Wow, Harry, this almost makes me want to run out and get a Suburban NT furnace, just because you've posted this great trouble-shooting guide. It must have taken you a while to type it all out. What a resource this group is!


Raya
Even better Raya, Harry lives about an hour from me. I'm starting to think with him that close I should install a Suburban NT heater....
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