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Laars Mini-Therm JVS160 short cycle

MandoMando Posts: 1Member
Hi Guys,

I have a residential Laars Mini-therm model JVS160NDIS  Serial # D02JE0076.

I had it installed new 6 years ago.  The unit has worked flawlessly until late last winter when it will ignite, run for 15-20 seconds, shut down, ignite again, run for 15-20 seconds........ Sometimes it will ignite and rum for a complete cycle until thermostat shuts it down. Thermostat has been replaced—no change.  Flue, pump, water supply are all fine.  Unit is super clean and well ventilated.  House heats fine, gas usage is the same.  Thanks for your help.


  • kcoppkcopp Posts: 3,324Member
    sounds like....

    the flame sensor is shot.
  • SlimpickinsSlimpickins Posts: 320Member
    check heat exchanger

    the flame rod being bad or dirty the flames would go out in 3 to 5 seconds. You might get an inspection mirror and look at the heat exchanger. A lot of Laars mini therms aren't piped correctly and the heat exchanger will clog from flue condensation. This will cause problems with the burner flame and cause the flame to lift off the pilot and shut it down. I've seen problems with ignition modules that would cause a similar problem. Good luck and keep us informed.
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