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Furnace Maintenance

furnace heater

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#1 Flyfisher


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Posted 23 June 2015 - 10:52 PM

I have a "05 Hawk with a Suburban furnace that some times works and some times shuts itself off after a minute of blowing. Perhaps it needs some maintenance. I have tried FWC site manuals, Suburban site and archives on this site. Brenda at FWC sugested a few Youtubes, but nothing seems to look like my model. Anybody done some service on theirs? Do you need to remove the whole thing to get to the burnner box?

Thanks, Gregg

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#2 MarkBC


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Posted 24 June 2015 - 12:41 AM

"shuts itself off after a minute of blowing"


This can be caused by the sail-switch not being "sailed" enough -- not being moved enough by the fan, and the furnace won't turn on the propane and light it if there isn't enough air blowing.  The leading cause of "isn't enough air blowing" is that the fan isn't getting enough power -- the battery voltage could be too low.  This certainly has been the explanation for the same thing in my furnace in the past.

Or could there be something wrong with the sail switch itself that keeps it from triggering the "enough blower" signal?


Can you hear the igniter clicking?  If so, then "isn't enough air blowing" isn't the problem because the furnace won't even try to light if there isn't enough air blowing.


I'm sure there are other explanations, but this has been my experience.

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FWC Hawk (2005) on a Ford F250 Supercab, 6.8L gas (2000)

#3 wuck


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Posted 24 June 2015 - 05:14 AM

 I think MarkBC might be on to something with the sail switch, some furnaces have issues at high altitudes with it.


I had the suburban furnace out of my hawk recently to look for an intermittent short (blown fuses). It wasn't too hard to get out. You have to remove the grill, cabinet face, electrical connections (4) and the gas line. Just a couple of screws at the lower front of furnace hold it in, you might need to tug a bit to release the vent pipes. I had a large clump of mud-dauber wasp nest in the air plenum, maybe yours does too causing sail switch issues. Gotta get a screen on there!


Couldn't find a short, but I re-dressed the wiring mess using split looms and tie wraps, particularly around sharp-edged brackets.

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#4 Sea Bear

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Posted 24 June 2015 - 05:55 AM

I had similar issues.  Furnace burner wouldn't kick in unless the battery was fully charged.  I found the sail switch arm was rubbing against the cover.  I bent the little wire arm and it works great now.  It must have gotten bent from vibration going down the road.


Be sure your batteries are full.  The sail switch is easy to test with a ohm meter.  You can hear it click when the fan comes on.  

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