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Furnace operation question Damien Hickey 10-8-15  
I am trying to troubleshoot an issue with my Suburban furnace not cycling properly. It will start up just fine from the thermostat (digital) but after reaching temperature and the stat turns the unit off, the furnace will not turn back on after the temperature falls a degree or two below the set temperature. If I wait a few minutes, turn the stat off and then back on again it will start up every time. It just wont start up by itself when the stat tells it to.

I've noticed the pilot light is going off after reaching temperature.

Is the pilot supposed to turn off after the stat reaches the set temperature and turns the unit off? (the pilot is lit electronically)

You can hear the stat kick back on and an electrical hum from the furnace but the pilot does not light and the fan does not turn on. I "tapped" my foot against it last night when this happened and it turned on! This got me thinking there might be a loose connector or something. I pulled the front cover and check the connections that I could and they all seemed normal. I might try disconnecting each connection and cleaning the spade terminals. Sorry I am at work right now and don't know the furnace model off hand but it is on a 2012 20' Palomino Trek G156.

Any thoughts?

ps. this happened with a mechanical stat as well, which is why i switched out to the digital.

Re: Furnace operation question BUBBA THE BUS TECH 10-9-15  
You have a bad "High Limit Switch"

This can be caused by closed or restricted dampers to try and "balanced" the heat flow or a throw rug or a flex duct with a kink or other restriction. The Palomino Plant loves to put extra flex duct in to make it easy to install the registers, problem is that the folded up duct blocks air flow and causes the furnace to overheat.

But it could just be a failed switch.

As you havent said what model furnace you have I can't direct you on how to repair it

Good LUck
Re: Furnace operation question Damien Hickey 10-12-15  
Hi Bubba, thanks for responding. The furnace is a Suburban NT20-SE and there are no floor vents or ducting so I am leaning towards the limit switch. It looks like its a fairly simple removal and install. How would I go about testing the switch? I read on another forum that there should be 12vdc on both sides of the switch when active. Is there anything else to test on the switch?

Thanks for your help.
Re: Furnace operation question BUBBA THE BUS TECH 10-14-15  
Both inside joke and valid test proceedure. Paper clip between the two wires. A jumper wire does just as well.

Be careful we are eliinating an important safety component for only!

If you can get to it and test it with an Ohm Meter while its tripped at works as well.

By the way the Joke is the paper clip shaped scar I have on my left index finger and thumb from testing a higher amperage than anticapated

It still makes me wince
Re: Furnace operation question Charles 11-16-15  
Diagram of how to manually light
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