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We_ride___'s avatar
We_ride___
Explorer
Dec 30, 2020

Suburban SF30F - intermittent reliability

Hi - SF30F Propane heater with a manual Dometic thermostat.

We placed a thermometer next to wall mounted thermostat for comparison.

Symptoms are unique:
- comes on and off at desired temperature during the day.
- around 2 or 3am abouts' it will not come on as it gets extremely cold.
- we get up and adjust the tempurature slide on thermostat - stays off.
- while we're still up, we turn the thermostat to OFF then back to FURNACE and it works for remainder of the overnight period.
- come the chilly morning, the same thing will need to be done to sort of manually reset 'something'.

New motherboard has been replaced this year, already.

Help?

Cheers

29 Replies

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  • Old-Biscuit's avatar
    Old-Biscuit
    Explorer III
    Dec 31, 2020
    Time Delay Relay is a stand alone component on furnace fan cover area

    Red/Blue Wires one side (DC+ from fused source/DC+ to thermostat_
    Red wire on opposite side (DC+ to Fan Motor)

    Blue/White Wires on other terminal (DC+ from thermostat/DC+ to Sail Switch)
    Green Wire on opposite side (Ground to Terminal Block)

    Should look similar to this (Suburban 231202 ---- shop around $50)
  • We_ride___'s avatar
    We_ride___
    Explorer
    Dec 31, 2020
    Thanks - Yes, a new thermostat was installed - because of these symptoms. Obviously the new thermostat didn't solve the issues.

    Is the time delay relay on the motherboard, or the circuit board of the thermostat?

    Cheers
  • enblethen's avatar
    enblethen
    Nomad
    Dec 31, 2020
    We ride: you have replaced the thermostat recently? It was a new replacement? With that information, I would then doubt it is the thermostat.
    I hate to through parts at a problem!
    When you get a chance, look closely at the time delay relay. You will be looking for black or blue connection points. Wiggle the wires watching for any movement in the relay.
  • We_ride___'s avatar
    We_ride___
    Explorer
    Dec 31, 2020
    thanks and just to confirm, you noted this is a newly replaced analog thermostat?
  • enblethen's avatar
    enblethen
    Nomad
    Dec 31, 2020
    I am thinking with the model(age) of the thermostat that it is failing.
    I would be trying to find a digital replacement.
  • We_ride___'s avatar
    We_ride___
    Explorer
    Dec 31, 2020
    Dometic D3106995.032 Heat/Cool Analog Thermostat...
    Six sockets are filled by six wires.
  • enblethen's avatar
    enblethen
    Nomad
    Dec 30, 2020
    Two items come to mind.
    Time delay relay and the thermostat.
    I would say circuit breaker on motor but did not see it listed under parts.
    Make and model of thermostat? pull cover off and check to see how many wires connect to it.
    Time delay relays seldom fail as they are rated for many thousands of operations. It is about 1 inch black cube.
  • We_ride___'s avatar
    We_ride___
    Explorer
    Dec 30, 2020
    Shore power - 13.8v across the posts and at the unit too.

    And it works normally when it does work.
    However, when it doesn't work - there is no click or fan cycling. Just nothing.

    I should also note the thermostat was recently replaced.
  • enblethen's avatar
    enblethen
    Nomad
    Dec 30, 2020
    Are you running on batteries or shore power? Low voltage could be problem.
    Is the furnace trying to start? Does the fan run?

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