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furnace

Todd757
Explorer
Explorer
2008 Fleetwood Discovery. Front furnace works fine. Rear furnace fan comes on but right about the time the igniter should come to life everything shuts down.

Any ideas?
3 REPLIES 3

wa8yxm
Explorer III
Explorer III
This document was created while I was diagnosing MY furnace.. I am told I missed one possible issue... Sadly I forget if I updated the document or not and the issue Bad connections anywhere along the line can lower voltage

When the T-Stat calls for heat the control board starts the blower (1)
The blower blows closing the sail switch (2)
The control board then opens the gas valve (3) and begins sparking (4.1)
Gas Flows (5) And ignitets (4.2)
The flame heats the flame sensor (5)
The flame sensor sends .480 volts to the control board (6)
which then detects the .480 and continues operation (*)
When the T-stat says "Enough already" (RV is now warm)
The control board shuts off the gas flow (*)
and then turns off the blower after a cool down (*)

*: At nearly every step the control board is involved. IF IT IS BAD, things will not work.. I recommend replacement boards from Dinosaur boards.. When Mine went out the Dino board was less than half the price and when opened the box the quality of construction and workmanship, and then design was very clear to my trained eyes.

0: No propane or propane TURNED OFF.. (I mean check the obvious first, In the original of this document I assumed you'd done that but.. Well.. I did not so....
1: No 12 volt to furnace, blower motor shot
2: Low 12 volt, air ducts clogged, blower "obstructed" bad sail switch
3: Bad solenoid, Clogged Gas Jet
4: .1: Bad ignition circuit (high voltage) on control board. .2: Points too wide (Very common it seems)
5: These do not often fail but they can
5: Bad connection, NOTE:
5 and * Bad wire.

* applies to all steps by the way So does bad wire/connection.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times

Chris_Bryant
Explorer II
Explorer II
If it shuts down that fast, odds are either the limit switch or sail switch are open. If it is a Suburban, try removing the interior panel and unplug and replug the leads on the limit switch- they often get oxidized on that model.
-- Chris Bryant

Mandalay_Parr
Explorer
Explorer
Sail switch must be activated by air flow.
Jerry Parr
Full-time
2005 Mandalay 40B
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