furnace fan worked Monday but now it is Wednesday

Discussion in 'General RVing' started by sp, Mar 22, 2006.

  1. sp

    sp Senior Member

    Hi All,

    Haven't been on in awhile but I'm getting the old dog (76 Prowler) readied for sale. Of course, in the Northeast, it is colder now than it was in January so I kicked on the duo therm Monday afternoon so I could start cleaning up. Turned the lp on, put the thermostat on for a few seconds to blow out any junk, lit the pilot, and both burners kicked on. I stayed out there for a few hours and it cycled on and off just like it has since I fixed it up in 03. This afternoon I go in and as soon as I move the thermostat I get a click from the furnace but the blower doesn't go on. I slid the thermostat back to the off position and it clicks again. I pulled the fuse and didn't get any clicks so I know it is not that. Any ideas??

    Thanks,
    Steve
     
  2. MOtech

    MOtech New Member

    furnace fan worked Monday but now it is Wednesday

    Make sure you have sufficient Voltage..need 10.5
    You can find out if the thermostat is bad by bypassing it, connect the 2 blue wires together and se if it works, if not sounds like its time for a new board.
     
  3. sp

    sp Senior Member

    furnace fan worked Monday but now it is Wednesday

    MOtech, Thanks for the response. My brother will bring his meter over to check it. I'm not sure if the voltage will drop like that because I'm running 110 thru the invertor. So, if I take the thermostat out of the loop and touch the two wires togeter, the fan/blower should go on? What about the fan switch between the thermostat and the fan/blower?

    No board on this old dog.

    Steve
     
  4. Kirk

    Kirk Senior Member

    furnace fan worked Monday but now it is Wednesday

    I don't have the manual for that vintage furnace, but there should be a relay that is supplied by the thermostat. Since the fan does not blow, it is pretty safe to say that it isn't a voltage problem as that would mean that the fan would blow, but not move enough air to close the sail switch. The relay supplies power to the blower motor and through the sail switch to the igniter ckrcuit board which then sends power to the gas valve and to the igniter. This does assume that you have a direct ignition furnace, since you don't mention lighting a pilot. I would suspect the problem ot be either in the thermostat or the relay, or power to one of them. But you have to use a meter to know anything sure. If you heard a click in the furnace, that would seem to indicate that the thermostat is working and the relay is closing. But with no meter, we are all just guessing. I would start by checking for at least 11V at the furnace supply and then go from there.
     
  5. ARCHER

    ARCHER Senior Member

    furnace fan worked Monday but now it is Wednesday

    My ole furnace stopped working here in Texas. Fan runs ok, but no ignition. Gonna check the sail switch, limit switch and the board. I'm guessing that I have enough power (volts) since the fan runs normally.
     
  6. sp

    sp Senior Member

    furnace fan worked Monday but now it is Wednesday

    Kirk, i did mention manually lighting the pilot in my first message. I don't see any circut board in the owners manual but I do see two relays. Can you explain what you mean by the furnace supply?

    Archer, when I had your problem a few years back with this one I found the following:
    Plenty of power being supplied.
    Hornet nest in the combustion chamber.
    Bunch of dust and dirt on the blower squirrel cage.

    I cleaned everything up, put it back together and it worked fine till Wednesday.ARRGG!!!

    Thanks,Steve
     
  7. sp

    sp Senior Member

    furnace fan worked Monday but now it is Wednesday

    Update:

    Well, my brother used the tester to check everything that we could without pulling the unit out. So, we couldn't get to the blower motor and that has to be the problem because the relay is kicking open when we turn on the thermostat. I priced out a replacement which will cost about $120. I'm trying to weigh out if it is worth buying the replacement, pulling the unit to fix it or just sell the camper with the furnace as is. It just agravates me that I rebuilt all of the exhaust on it, hand cut every gasket for the combustion chamber, and had it running perfect until last week.

    Any thoughts either way??
    Steve
     
  8. s.harrington

    s.harrington Senior Member

    furnace fan worked Monday but now it is Wednesday

    Could still be the relay. Just because it clicks doesn't mean the contacts are good. That one has the old glass to relay. But you are probably going to find that your blower motor is bad. Is that a 65925 or 65930 model or bigger? I may be able to get the motor cheaper than $120.
     
  9. s.harrington

    s.harrington Senior Member

    furnace fan worked Monday but now it is Wednesday

    Just looked it up. My most expensive Duo-Therm 659 series motor is $95. However if you have a 653 series I would need the number off the motor to find it.
     
  10. sp

    sp Senior Member

    furnace fan worked Monday but now it is Wednesday

    it is the 65900/3-12792. if i pull it and find that the blower motor is good, do you have the relay available? how much? I also have a fedex or ups account number to ship with.

    thanks for checking on this for me!!

    still not sure if it is worth it to fix it or sell as is????
     
  11. s.harrington

    s.harrington Senior Member

    furnace fan worked Monday but now it is Wednesday

    I'll have to go looking in my junk drawer(lol) but I 'm sure I have one, I have a full furnace in the 40000 btu range in storage. I'll go find it for you. You can have it for $15.00 if you need it.
     
  12. sp

    sp Senior Member

    furnace fan worked Monday but now it is Wednesday

    SH: Thanks for the info. I've got the camper up on ebay and if the furnace is going to be a deal breaker than I'll fix it.

    I still need to check on the fridge. Do happen to remember the issue? I'll find the thread and put it back up to the top.

    Steve
     

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