Heater wont run on 12V

Discussion in 'Heating / Cooling Systems' started by johnandhis4x4, May 19, 2016.

  1. johnandhis4x4

    johnandhis4x4 Improvise, adapt, overcome

    19
    0
    Feb 15, 2011
    HI everyone!
    I am having an issue with my Atwood furnace (7916-II) in my 98 Coleman Santa Fe.

    Here's the problem:
    When utilizing the battery (12V) to power the furnace, the blower spins, the igniter clicks, but ignition does not occur. (I have a video, ill upload it later)

    When plugged in to 120V the heater starts as normal.

    I have notice that the blower runs significantly slower utilizing the 12V power supply.

    Things I know:
    I have a full LP tank, and I have a brand new (load tested) battery (I have used a different load tested battery from my boat and achieved the same result).

    I don't know where to start the check process as I have never touched the insides of a heater before. I have (and have read) the manual, but with the furnace functioning normally on 120V, I didn't any solutions.

    I am currently thinking a loose ground or Power connection (on the 12V side), but I would love to get some advice from others if they have any input.
     
  2. Raycfe

    Raycfe Waterford Ct.

    13,811
    894
    Oct 3, 2007
    Waterford, Ct
    If the battery is installed backwards the furnace will not work. Just something simple to check. White ground (-) black w/fuse holder/circuit breaker to (+).
     
  3. Antipodes

    Antipodes Call me Paul

    773
    75
    Jan 28, 2015
    Christchurch, New Zealand
    Hi,
    Almost certainly the sail switch which will not turn on the ignitor or gas if there is insufficient wind speed is stopping it from running.
    As you say the unit runs a lot slower on 12V then I guess it is your battery which could be getting flat or has insufficient retained voltage.
    The heater only uses 12V to function and uses the converter which supplies 12Volts from the 120V supply, at the same time as charging your battery and will be around the 13 Volt mark (Or mnre)
    But as you have tried this with multiple batteries, it is possible that the bearings in the fan are getting sticky and it just does not go fast enough on only 12 v from the battery.

    Download the manual for the furnace. Some of the units have a series of leds which will blink different configuration modes depending on the failure mode.

    Ok had a quick look at the service manual and it does not have LEDs on the main board, so it will be a matter of checking your voltage at the unit with just Battery and then with the trailer connected to mains power..
    Go forward from there.
     
  4. johnandhis4x4

    johnandhis4x4 Improvise, adapt, overcome

    19
    0
    Feb 15, 2011
    I have verified that its correct. The problem started about a year after I replaced the original battery, and I have verified + and - while plugged into 120V.
     
  5. johnandhis4x4

    johnandhis4x4 Improvise, adapt, overcome

    19
    0
    Feb 15, 2011
    Its not the battery, I have had it load tested along with a boat battery that is larger (group 29 over 24) and using both batteries (at different times) resulted in the same outcome.

    The problem with your bearing theory is that the furnace runs fine when using or plugged into 120V, which is why I am stumped.

    Mine doesn't have any LED's that I can see, but ill look closer this weekend.

    Thank you for your help. =-)
     
  6. Antipodes

    Antipodes Call me Paul

    773
    75
    Jan 28, 2015
    Christchurch, New Zealand
     
  7. johnandhis4x4

    johnandhis4x4 Improvise, adapt, overcome

    19
    0
    Feb 15, 2011
     
  8. R00

    R00 Active Member

    1,286
    15
    Aug 10, 2014
    Check the voltage at the furnace, it's possible you have frayed wiring or a bad ground on the furnace and this is causing insufficient voltage to the fan to spin fast enough to trip the sail switch.
     
  9. Antipodes

    Antipodes Call me Paul

    773
    75
    Jan 28, 2015
    Christchurch, New Zealand
  10. jwdogman@yahoo.com

    jwdogman@yahoo.com Member

    35
    0
    Jan 13, 2016
    I am having the EXACT same problem with my 98 Palomino Pony's furnace! [?:~{]
     
  11. Customer

    Customer Well-Known Member

    2,425
    227
    Jun 5, 2014
    If the battery is weak or the connections are poor the fan will not spin fast enough for the sail switch to close. If the sail switch stays open the gas valve will not open.
     

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