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Old 01-06-2014, 12:55 PM   #1
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Suburban furnace SF

My Alfa Gold (2000) Suburban furnace does not start. The air and heat pump are working properly. 12V is present at the furnace and the call for service from the T stat is working on both control lines. When a furnace call for heat is sent, the blower does not start. The sequence of events in the manual state in part that the module board checks the sail switch circuit status is open and starts the blower. Local techs think, but are not sure, the blower motor should start regardless of the sail switch status. The sail switch seems to be the most common problem with these units. Comments please.

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Old 01-06-2014, 03:14 PM   #2
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Usualy when the blower does not start, the problem usualy comes from the house batteries, have you tried with house power 120V ,

Mike, Martina and Maya our yellow Lab
2013 CrossRoads, Cruiser 29,5 ft 5thWeel, 2010 Ram HEMI 1500
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Old 01-06-2014, 03:27 PM   #3
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The sail switch doesn't come into play until the blower is running. The blower should start running, sail switch confirms that the blower is running and after approx. 30 sec to ensure gasses & vapors are cleared ignition starts sparking & gas valve opens.

If calling for heat does nothing, check 12vdc at the furnace, if good then probably a board replacement is needed. Yes the board is the most common replaced part not the sail switch - can't even remember the last time we changed a sail switch, boards are always on the shelf, and always use dinosaur boards over oem. Longer warranty & fuse protected.
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Old 01-07-2014, 02:44 AM   #4
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Thank you both. Mike, it is connected to shore power. Jim, is the pause relay integrated in the dinosaur board?
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Old 01-07-2014, 03:06 AM   #5
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I would start with the overtemp sensor... it's the 1st item inline. If the overtemp sensor has failed or tripped it will not even start the pre-ignition draft process, which would then be followed by the sail switch check prior to opening the gas valve.
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Old 01-08-2014, 04:09 AM   #6
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The over temp lock out is good. It seems that the power is not getting past the pause relay which starts the blower motor. If the pause relay is good, the blower motor is in question. My question is, the pause relay. Is it integrated on the module board? I think I am going the do without the furnace till I get back home in the spring. The heat pump is working well and if it gets to cold for the pump I have couple of space heaters as back up. I like boon docking when I am moving. If I see a nice spot, I stop to "smell the roses" and the furnace makes life easier when shore power is not available.
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Old 01-08-2014, 08:01 AM   #7
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If there is power coming into the board but nothing coming out of the board to the motor, you need a new board.
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Old 01-08-2014, 11:19 AM   #8
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Do the easiest thing first - disconnect from shore power and disconnect your batteries for a minute. Then reconnect and try it.

Good luck,


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