Suburban Nt-32 Does Not Work

elliottkatz · 11-10-2007, 09:10 AM

Hi Everybody,
Every fall I write on the forums here as the cold drops in and I'm forced to turn on the heater. Last year my pilot needed cleaning, and this year I have no idea how to fix the furnace. It started out like this: the furnace would turn on and heat up to the temperature on the thermostat and then would shut off. When it went to cycle again, the blower would come on for ten seconds and then would shut off immediately. It would continue to turn on and off like this until I switched off the unit at the thermostat. I thought the thermostat might be acting up because when I pulled it off the wall and "shorted the circuit" by connecting the two wire ends, the heater turned on perfectly. But now, after fiddling with the unit for another week, the bypassing trick at the thermostat ends doesn't work. I get no response from the furnace at all. After reading a number of these forums I've deduced that the problem could be coming from any number of parts in the unit... the circuit board, the thermostat relay, etc. Does anybody have any tests I could do to narrow my search? Or any other advice that would be useful for getting heat back in the trailer? In VT where it gets rather cold.

Thanks! Elliott

cooperhawk · 11-10-2007, 09:19 AM

I just replaced the circuit board in my Suburban with a "dinasour" circuit board and it solved all my problems. You can find them on line.

elliottkatz · 11-10-2007, 10:13 AM

Cooperhawk,
Thanks for the reply. Did the symptoms I listed in my first forum sound similar to the problems you were having before replacing the circuit board?

Jim in Pima · 12-10-2007, 04:09 PM

Question, does the NT32 have a circuit board, mine is the old pilot light heater. I would check for a loose or corroded wire from the thermostat for the problem. Or a loose wire on the fan switch..

lewster · 12-10-2007, 06:13 PM

You could have any number of problems.

First I would remove the furnace from the trailer to better access all of the components for bench testing. Check all of your wiring connections first and be sure they are clean and tight. Be sure that you are getting 12VDC on the power leads feeding the furnace. If you have a circuit board, remove the plug and clean the contact area on the board with a pencil's eraser. Then place and remove the plug a few times the clean the contacts on the plug itself.

Next, hookup the power leads to a 12VDC battery and the LP to an LP tank from your barbecue grill with the regulator in place. With everything connected, join the 2 blue thermostat leads together and see if the fan starts. If so, the unit should purge the plenum and fire in 15-20 seconds.

If it does not fire, remove the voltage and LP and look at your sail switch and test it for continuity. If that is OK, look at your limit switch and test for continuity. If that is OK, remove the leads from the gas valve and apply 12VDC directly to the valve. You should get a click that shows it is opening.

If everything is OK and you do have an igniter board, I would replace it at this point, or have yours tested at any well equipped RV shop. If you do not have an igniter board but a time delay relay (TDR), I would look into replacing that.

Hope this helps!

Quote:

Originally Posted by elliottkatz

Hi Everybody,
Every fall I write on the forums here as the cold drops in and I'm forced to turn on the heater. Last year my pilot needed cleaning, and this year I have no idea how to fix the furnace. It started out like this: the furnace would turn on and heat up to the temperature on the thermostat and then would shut off. When it went to cycle again, the blower would come on for ten seconds and then would shut off immediately. It would continue to turn on and off like this until I switched off the unit at the thermostat. I thought the thermostat might be acting up because when I pulled it off the wall and "shorted the circuit" by connecting the two wire ends, the heater turned on perfectly. But now, after fiddling with the unit for another week, the bypassing trick at the thermostat ends doesn't work. I get no response from the furnace at all. After reading a number of these forums I've deduced that the problem could be coming from any number of parts in the unit... the circuit board, the thermostat relay, etc. Does anybody have any tests I could do to narrow my search? Or any other advice that would be useful for getting heat back in the trailer? In VT where it gets rather cold.

Thanks! Elliott

ronsgto · 09-17-2008, 05:26 PM

I have been trying to get some help on my NT-32. When I try and light the pilot it lights but somehow LPG builds up and poof flame out the front last time burned the hair on my arm. What is causing the build up of LPG before I can even let go of the reset button. I checked the thermostat and it is set to off. I have tried it several times and it is kind of scarry. Any one on the forumn that is real familiar with these. I would appreciate any help.

olddog299 · 09-20-2008, 04:57 PM

Most likely it needs cleaning - flakes of rust, wasp nests, spiders webs, etc. are the most likely culprits. Follow Lew's instructions above, or take it to a certified RV tech. These things are hazardous if you don't know what you are doing. Explosions and blowbacks, formation of CO, fires -- is it really saving money when you put you and your family's lives in the mix? It IS possible to service these units properly, but it isn't to be undertaken lightly.

ronsgto · 09-20-2008, 08:09 PM

I appreciate all the info and of course I do not want to endanger my family. By know means am I blowing my own horn but I have been doing mechanical repairs for years so I wanted to look into what might be wrong. I pulled the furnace out and that was quite a challenge. Yes I found a lot of dirt and wasp nest. Not much rust though. Pulled out the burner and blew it out with compressed air. I have concluded that the main problem is with the gas valve. Pulled the valve and put a small baloon on the main burner line. Pushed the pilot reset button and the baloon started to inflate. That should not happen, gas is by passing. Pulled the valve apart cleaned the rubber diaphram and its surface. Make a long story short reinstalled it and everything is working as it should. The baloon no longer inflated. I will be installing a CO warning device as a saftey measure. I also use a tool to check for leaking LPG when ever I finish repairs like this. Thanks again for the input this is a great site.

Mike Leary · 09-20-2008, 08:25 PM

These things don't last forever; I'd of replaced it long ago.

olddog299 · 09-21-2008, 01:22 AM

That's great to hear, Ron. Order yourself a replacement valve as I suspect you're going to need to replace it sooner than later.