Forum Discussion

not_enuf_toys's avatar
not_enuf_toys
Explorer
Jun 27, 2015

furnace blower motor when thermostat switched to on

First, thanks for taking a look at this. I appreciate any help you can give me.

2007 forest river Salem 30QBSS
Suburban furnace
Dometic AC

Everything worked great at first. ac, furnace, auto, on, hi/low speeds.

the issue is, when I used to switch the thermostat from auto to on, the blower motor in the furnace used to kick on (when just on 12v). Now (still on 12v) when I click the switch from auto to on, the ac makes a one time click noise and the blower in the furnace never turns on. when plugged into 110, and switch from auto to on, the ac blower kicks on.

have tried a new thermostat and still the same results. I am thinking something goofy has happened with the furnace or analog controls but not certain.

Any thoughts? ideas? things to try?
  • not_enuf_toys's avatar
    not_enuf_toys
    Explorer
    Jun 27, 2015
    budwich wrote:
    sounds more like your thermostat has the "cool" function selected as opposed to "heat". The fan functon directs power to the appropriate fan unit based on that. Of course, the AC fan needs 120v to run which won't happen on 12v power. Hence, what you are observing appears to be normal.


    I have tried switching from auto to on in all three modes (cool/off/heat), and still just a click sound from the ac
  • not_enuf_toys's avatar
    not_enuf_toys
    Explorer
    Jun 27, 2015
    Lazydude wrote:
    The only way to tell if the curcuit board is bad is to replace it, so you might want to take it to a RV repair place and let them do it. It cost me 350 bucks cdn to have mine fixed.


    I will take a look at the board. as a side note, when heat is needed, and the furnace actually kicks on, the blower works just fine. problem is only when wanting to run just the blower
  • not_enuf_toys's avatar
    not_enuf_toys
    Explorer
    Jun 27, 2015
    Lazydude wrote:
    The only way to tell if the curcuit board is bad is to replace it, so you might want to take it to a RV repair place and let them do it. It cost me 350 bucks cdn to have mine fixed.


    I will take a look at the board. as a side note, when heat is needed, and the furnace actually kicks on, the blower works just fine. problem is only when wanting to run just the blower
  • budwich's avatar
    budwich
    Explorer
    Jun 27, 2015
    sounds more like your thermostat has the "cool" function selected as opposed to "heat". The fan functon directs power to the appropriate fan unit based on that. Of course, the AC fan needs 120v to run which won't happen on 12v power. Hence, what you are observing appears to be normal.
  • Lazydude's avatar
    Lazydude
    Explorer
    Jun 27, 2015
    The only way to tell if the curcuit board is bad is to replace it, so you might want to take it to a RV repair place and let them do it. It cost me 350 bucks cdn to have mine fixed.
  • not_enuf_toys's avatar
    not_enuf_toys
    Explorer
    Jun 27, 2015
    Lazydude wrote:
    I had the exact same thing happen to me last year and it turned out to be a stuck relay on the furnace board. I could bang on the furance to get it to start some times but after awhile even that did'nt work. They had to change out the whole board to fix it.


    failure of sounding dumb - "on the furnace board"? is that physically on the furnace motor? I can take a look at that in the next day or two when I am back at the camper
  • Lazydude's avatar
    Lazydude
    Explorer
    Jun 27, 2015
    I had the exact same thing happen to me last year and it turned out to be a stuck relay on the furnace board. I could bang on the furance to get it to start some times but after awhile even that did'nt work. They had to change out the whole board to fix it.
  • VTR's avatar
    VTR
    Explorer
    Jun 27, 2015
    I had a thermostat and furnace issue this last trip, Following thread--

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