SUBURBAN FURNACE-HELP

Discussion in 'Talkback' started by ARCHER, Feb 18, 2006.

  1. ARCHER

    ARCHER Senior Member

    Hey folks,
    I just tried to turn my furnace on and it does the following:
    1. Turn on on/off switch
    2. Set Thermostat to 72 degrees
    3. After about 30 seconds, the blower fan comes on but no heat. In the past the heat would come on FIRST and then the blower would come on and all was fine. Ran the furnace one or two nights back in early December but not since then. Just filled the LP tank yesterday.
    I've checked the thermostat, cleaned the main contact to thermostat and blown out the thermostat with compressed air (can for PC). I've read that it might be air in the line and to bleed the line, but I'm not sure how to do that....the water heater works fine.
    We are not gonna freeze tonight, since I have an electric heater that is plugged in, but will be heading north on MOnday and want to make sure the furnace works if I need it there.
    Any ideas as to what might be the problem, since it worked fine in Dec but not now????? :dead: :sleepy: :disapprove:
     
  2. team3360

    team3360 New Member

    SUBURBAN FURNACE-HELP

    Archer, sounds to me like air in the line. were you out of propane when you filled or did you fill only one bottle(if you have two) . generally the furnace will cycle itself to clear the line of air. try burning all the stove burners for about 2 minutes.otherwise you might need to crack a fitting to bleed off the air. Just be sure to let the area air out good before letting the furnace start up. be sure to check the fitting with soapy water if you have to bleed off. LEE
     
  3. Grandview Trailer Sa

    Grandview Trailer Sa Senior Member

    SUBURBAN FURNACE-HELP

    Archer,
    Could be air in the line, and that would be great. That will cycle out after a few attempts. You could crack the line going into the furnace and that would take care of that. A Suburban fan runs 15 seconds and if the "sail" switch senses the air movement from the fan, it will open the gas valve and activate the ignitor to light the gas and there is your heat. If the sail switch does not work or there is no flame, the fan cuts off after 90 seconds. There is also a "over limit" switch and if that is stuck, there will be no heat.

    Let us know if there was air or something else. If not air, tell me exactly what it is doing and I will try to help.
     
  4. ARCHER

    ARCHER Senior Member

    SUBURBAN FURNACE-HELP

    Tks,
    I have one large perm LP tank. It was about 1/3 full when I refilled. The gas water heater w/electronic ignition works fine. I will try the gas stove and run it for a few minutes (all four burners and maybe the oven). The furnace tried to cycle about 6 times and I finally just shut it off. The wind has been extreme here this winter in Port Isabel, so maybe it has blown dirt/sand/who knows what into the intake hole on side of MH and gotten things dirty/stuck maybe.
    I'll see what I can do myself. Not too cold, as I ran the small electric heater and it is suppose to warm up on Monday.
    Grandview, the fan will come on when I turn the furnace on and turn the thermostat up and will not turn off until I turn the furnace off but the air feels like air conditioning not heat, so I am assuming the air I feel is from the outside intake opening.
     
  5. dennis1949

    dennis1949 Senior Member

    SUBURBAN FURNACE-HELP

    Mine did the same thing. Found out I had moisture in the line to the heater. Fan would come on but furnace would not light. The water heater and stove worked find. It had been about a year since I had used the furnace. Moisture was in the line for the furnace only. Took line apart and dried it out and has worked fine since. Found out I had some old propane in the tank I had switched to. Good Luck
    Dennis
     
  6. ARCHER

    ARCHER Senior Member

    SUBURBAN FURNACE-HELP

    Thanks Dennis.
    I ran the LP on the stove for about five minutes. Tried to start furnace again...no luck. Fan came on again but no heat at all. I checked intake/exhaust ports outside. Intake is sucking in air and exhaust is blowing air out. Furnace worked fine just 6-8 weeks ago so I don't think it is moisture in the lines, because LP is not "old". Filled tank last fall (Nov) and again Friday, so LP is pretty good.
    After I get to Rockport tomorrow, I'll open the furnace access and see if it is dirty, etc.
    Grandview, any suggestions on exactly what to look for or do while I have access to furnace?
    Stayed warm last night.... :cool:
     
  7. Grandview Trailer Sa

    Grandview Trailer Sa Senior Member

    SUBURBAN FURNACE-HELP

    Archer, take return air panel off from the inside and you will see the back of the furnace. Take the back cover off that is held on by 2 screws. You will see 2 wires going to the over limit switch. If you have an ohm meter, the switch should be closed. If open, that is probably you problem. If you don't have a meter, jump the wires together and run the furnace. You won't hurt anything jumping the wires since the switch is usually doing just that and breaking the circuit when it does overheat. IF you get heat with the wires jumped, just replace the limit switch.
    If that does not do it, you will have to take the outside access cover off and check the sail switch. That is on the right side of the fan cover. It is a small micro switch that that has a long "sail" on it. The air closes the switch when the fan motor moves enough air to move the "sail". Again, you will see 2 wires going to the switch. Again, check with ohm meter or jump wires. This time the switch should be OPEN when the fan is not running and close when it starts.
    If all that checks out, my guess is you have circuit board problem.

    How old is your unit? If it happens to be under warranty, I can give you Suburbans number and you can call them. Even if not in warranty, they will help you figure it out.
     
  8. ARCHER

    ARCHER Senior Member

    SUBURBAN FURNACE-HELP

    Grandview, tks.
    My unit is by no means in warranty (89 Winnebago Chieftain). To be honest with you, I do not know where the return air panel is located. Is it inside MH? I know the furnace is located below the stove, but there is no panel beneath the stove or any cold air return there. There is a vent opening below the refrigerator but it houses piping, and wires, etc. and I cannot even see the furnace from there. I can access the furnace from the outside ia the cover over the intake/exhaust pipes. In checking wires (limit switch) Closed meaning a zero reading and open meaning resistence.
     
  9. Grandview Trailer Sa

    Grandview Trailer Sa Senior Member

    SUBURBAN FURNACE-HELP

    Usually the cold air return vent is close to the furnace on the inside. It is real nice when it is directly behind the furnace. I don't know where it is in your motorhome. Zero will be the closed reading.
     
  10. Kirk

    Kirk Senior Member

    SUBURBAN FURNACE-HELP

    Archer,

    If you visit http://bryantrv.com/docs.html you can down-load the service manual for the furnace that you have. A Suburban furnace of that vintage does not have the blower cut-off feature and the blower will continue to run indefinately.

    And don't get in any hurry coming up this way as it is cold here! We are about two hours north of Rockport near Lake Jackson.
     
  11. Grandview Trailer Sa

    Grandview Trailer Sa Senior Member

    SUBURBAN FURNACE-HELP

    Thanks Kirk, I was wondering about that.
     
  12. s.harrington

    s.harrington Senior Member

    SUBURBAN FURNACE-HELP

    Dollars to doughnuts its one of two things. You either have a bad electrode or a bad circuit board. If it is a NT series furnace to get to the electrodes all you have to do is take off the front door of the furnace by removing the screws on either side then look for the site-glass. under the site-glass you will see wires and electrodes on a plate with 2 hex head screws. remove the srews and the electrode assembly will come out (be carefull of the gasket). If the electrodes are swollen and cracked at the ends replace them. To get to the circuit board you have to pull the furnace out of its case. Unless you have done this you should leave that up to a proffessional.
     

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