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 > Furnace blowing cold air only

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RollandBC

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Posted: 09/02/19 11:34am Link  |  Quote  |  Print  |  Notify Moderator

Hi, I have a 1995 Prowler 22' and it seems like the furnace is only blowing cold air.
It does state there is an AUTO Igniter but I can't see the pilot or flame or smell gas.

Old-Biscuit

Verde Valley

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Posted: 09/02/19 11:44am Link  |  Quote  |  Print  |  Notify Moderator

T-stat closes sending DC to furnace
Furnace Blower starts and comes up to speed......purge cycle to clear combustion chamber

SAIL SWITCH MUST close before DC will continue thru circuits for gas valve/spark electrode operation

SAIL SWITCH...has a 'paddle' that sticks out into fan blower chamber.
Air flow moves paddle closing the micro switch allowing DC to continue
Sail Switch gets dirty/sticks/fails.....no matter how long fan runs Sail Switch MUST close for furnace to light off main flame via spark electrode

Sail Switch typically has 2 wire wires....12VDC+ In/OUT of switch
Switch can be under cover over motor of next to blower area


Is it time for your medication or mine?


2007 DODGE 3500 QC SRW 5.9L CTD In-Bed 'quiet gen'
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enblethen

Moses Lake, WA

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Posted: 09/02/19 12:56pm Link  |  Quote  |  Print  |  Notify Moderator

Make and model of furnce?
DSI (direct Spark Ignition) does not have pilot.
Odds are the sail switch is dirty. The arm of the sail switch sticks into the blower. The switch is small located outside of the blower area. You can on some use compreesed air to blow even a spec of debris out of the sail switch.


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midnightsadie

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Posted: 09/02/19 02:21pm Link  |  Quote  |  Print  |  Notify Moderator

and if is the first time starting it,? light the stove to purge the lines of air, on first time start up ,some times it,ll try a few times.

RollandBC

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Posted: 09/02/19 02:30pm Link  |  Quote  |  Print  |  Notify Moderator

Ok I did start the stove and got it working to verify propane.
It's the Excalibur 8500 series Model 8520-lll
I do have a picture but I need to host the pic somewhere.

RollandBC

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Posted: 09/02/19 02:32pm Link  |  Quote  |  Print  |  Notify Moderator

So is the SAIL switch under the Breaker on the left?

DownTheAvenue

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Posted: 09/02/19 02:38pm Link  |  Quote  |  Print  |  Notify Moderator

First understand how a RV furnace works which is very different from a residential furnace:
1. Thermostat calls for heat
2. Blower motor turns on and blows cold air out of the vents
3. Blower motor continues to run for several minutes
4. Burner ignites and gradually warms the heat exchanger
5. Air blowing out the vents gradually warms as the heat exchanger warms
6. Thermostat is satisfied and turns off the burner
7. Heat exchanger gradually cools
8. Air blowing out the vents gradually cools as the heat exchanger cools
9. Blower motor shuts off

It may take several cycles of the blower motor coming on and the burner trying to ignite until it finally ignites if the RV has been sitting or you changed a propane tank. If the burner does not ignite after a very short time, then the blower motor will turn off.

If you turn down the thermostat before the burner ignition cycle starts, the blower motor will turn off.

There are several safety devices built into the furnace that can prevent the burner from igniting. They can be doing their job correctly, or they could be faulty.

RollandBC

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Posted: 09/02/19 02:46pm Link  |  Quote  |  Print  |  Notify Moderator

Ok thanks.
1) the thermostat does call for heat
2) the Blower does tutn on and blows cold air
3) motor does run
4) I do not hear any ignition noises at all >> blower still running
5) I waited maybe 10 minutes >> no warmth >> maybe I should wait longer?

I will fire it back up now and see what happens
I'll post back

enblethen

Moses Lake, WA

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Posted: 09/02/19 02:55pm Link  |  Quote  |  Print  |  Notify Moderator

No, it is on top of the blower housing. Look on top of the larger blower housing, between it and the top of the furnace housing on the right side. It is very small rectangular object. About 3/8 thick and 3/4 inch square with metal arm sticking out to the left into blower housing.
Item 48 on page 37
Parts breakdown

RollandBC

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Posted: 09/02/19 03:06pm Link  |  Quote  |  Print  |  Notify Moderator

ok there is only 2 black boxes
1 on the left is Breaker with littlte push button
and 1 black rectangular box on the right at top
has 4 wires going into it and 2 screws holding in
Do I remove those screws to clean it or do I remove the 4 screws holding in the face of the blower?

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