Forum Discussion

mowtown's avatar
mowtown
Explorer
Jan 22, 2014

Dometic interior heater turning on and off constantly

I have a 2013 Prime time Crusader bunk house with a 35k btu heater, the issue I'm having is that when it's set on a certain temp say 60 the heater blower kicks on then moments later the burner fires and I start getting heat then almost right away it shuts off, 60 seconds go by then the whole process starts over and it does this all night but never running long enough to warm the camper, but if I bump the thermostat up to 65 or 70 it will stay running perfectly fine and warm things up it just doesn't want to work right at a set temp, this sounds like a bad thermosat to me, what do you think??? When I bought this camper almost a year ago it did this but not to this extent so when I got home for the first time I took the wooden cover off to expose the heater in side the camper and was shocked to see a large hole in the floor where they brought the drier hose up and also no foil tape on the joints so I sealed the hole and fixed all the loose joints and also droped the corplast to check all heater piping and all was good, also I have tried running the A/C blower to circulate the air better and this changed nothing.
  • katysdad's avatar
    katysdad
    Explorer
    Jan 23, 2014
    being a 2013 it probably has a digital thermostat. OP did not mention brand or type. If so offbrand t-stats or twisting wires together will not work and may damage an expensive control box that is actually in the A/C.
  • N-Trouble's avatar
    N-Trouble
    Explorer
    Jan 22, 2014
    Remove thermostat and short the leads together to turn the heater on. DOes it remain on? If so, you have a bad thermostat.
  • 0rion's avatar
    0rion
    Explorer
    Jan 22, 2014
    quick question before you go down the road of replacing the t-stat.
    If you turn it on and the burners light and then it kicks off. The next time it comes on do the burners light or if you raise the temp will it light without having to turn it off and back on?

    I want to make sure the switch on your induction fan isn't the culprit. If that switch doesn't sense enough air draw it will shut the furnace down and put it into safety lock out which means you have to turn it off and back on to get it to light again. That was why I asked earlier about shore/battery power. I had a camper once that the heater would run fine on shore but gave me problems on battery. It was because the fan didn't spin fast enough to close that switch.
  • 0rion's avatar
    0rion
    Explorer
    Jan 22, 2014
    it really does sound like a t-stat issue. Where is the actually pointer on your anticipator pointing too though? It'll be in amp tenths like .3 or .4 or something like that. I'm going to guess that's either way out of adjustment ( try it ~.36 to start) or it's bad. That would be my guess.
  • Old-Biscuit's avatar
    Old-Biscuit
    Explorer III
    Jan 22, 2014
    If the furnace short cycled with temp set high then it would point to being a furnace problem......

    BUT
    it only short cycling when close to temp set point (and working fine at higher degree setting) points to t-stat being problem.

    For $20-$25 pick up a battery operated digital t-stat (Hunter is used a lot) and replace your t-stat.

    Set it for 65*F furnace will stop at 66*F and come back on at 64*F
    Some 1*F diff. for A/C operation
  • elivi8's avatar
    elivi8
    Explorer
    Jan 22, 2014
    It sounds like the differential is not working as you eluded to. I would replace it.

    Ryan
  • mowtown's avatar
    mowtown
    Explorer
    Jan 22, 2014
    Yes once it reached a set temp it will short cycle after a few minutes also it does not change anything weather or not its on shore power or not and there are no vents blowing on it. Forgot to mention it but I set the temp differential to 1 degree and that changed nothing to. Like I mentioned before if I crank the temp up real high the heater will run great getting up to that temp, it just likes to short cycle after it gets there.
  • elivi8's avatar
    elivi8
    Explorer
    Jan 22, 2014
    I would check to see if there is a vent blowing right at the thermostat. This would cause the stat to heat up reaching setpoint then turning off right away. When the fan stops blowing air at it the temperature will drop causing the cycle to start again.

    Ryan
  • 0rion's avatar
    0rion
    Explorer
    Jan 22, 2014
    if you put it on 70 does it work like it should or does it short cycle once it hits the set temp? Where's the anticipator set at on the t-stat. Does it matter if it's on shore power or battery?

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