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Topic: Rear furnace not working (Read 763 times) previous topic - next topic

Rear furnace not working

My bedroom furnace does not fire up. It will start and run but it never ignites the flame for the heat. Is there a gas shut of for this or is it something else? I don't think this one has ever been used. Any help would be great. Still stuck up here in Northern Wisconsin and needing the heat now.  :-(

Can't wait for October 29th we are out of here fulltiming.  :)
Thanks,
Dave
Dave & Cris
1989 36' U280 Grand Villa SBID #3407

Re: Rear furnace not working

Reply #1 –
Would help to know the make of the furnace.

Clean all your furnaces electrical connections.  The ones you can separate, pull apart and clean them, then put them back together.  If there is a control board that pulls out, pull it out and clean those connections and put it back together.  CRC makes some very good electrical spray cleaner and is usually available in the big box stores such as Wallyworld.  You can also find cleaners at Radio Shack.

After all that blow out the furnace housing and clean the burners.
1994 U225
build #4514

Re: Rear furnace not working

Reply #2 –
Pat it is the Hydro Flame Excalibur II 16,000 BTU
Thanks
Dave
Dave & Cris
1989 36' U280 Grand Villa SBID #3407

Re: Rear furnace not working

Reply #3 –
OK, let's see how far in the sequence you get. When the thermostat signals the furnace to turn on:

The fan starts.  If the fan is moving enough air, the SAIL SWITCH is closed.  Low voltage at the furnace, restriction in the air return or restriction in outlet(s) (such as closed vents) can cause the sail switch to not close.

The sail switch closed signal goes to the heater PC board.  The PC board then does two things-- it sends 12 VDC to the GAS VALVE to open it and at the same time triggers the IGNITOR.  You should be able to clearly hear the "clicking" of the ignitor and can measure voltage to the gas valve and likely feel it click open if you put your finger on it (careful to be out of the exhaust area). 

The next step is for the flame to close the thermocouple that will signal the PC board that flame is present and therefore the gas valve should remain open/furnace continue to run.

Let us know at what point this process fails.

Brett
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Rear furnace not working

Reply #4 –
Quote from: wolfe10 –
OK, let's see how far in the sequence you get. When the thermostat signals the furnace to turn on:

The fan starts.  If the fan is moving enough air, the SAIL SWITCH is closed.  Low voltage at the furnace, restriction in the air return or restriction in outlet(s) (such as closed vents) can cause the sail switch to not close.

The sail switch closed signal goes to the heater PC board.  The PC board then does two things-- it sends 12 VDC to the GAS VALVE to open it and at the same time triggers the IGNITOR.  You should be able to clearly hear the "clicking" of the ignitor and can measure voltage to the gas valve and likely feel it click open if you put your finger on it (careful to be out of the exhaust area). 

The next step is for the flame to close the thermocouple that will signal the PC board that flame is present and therefore the gas valve should remain open/furnace continue to run.

Let us know at what point this process fails.

Brett
Brett, i get all the way to waiting to hear the clicking and it never happens. I compare it to the front one as far as the fan starts and blows air but never gets to the next step of the clicking to try and ignite.

I have to run to town and will be back later today to try and get this figured out.
Thanks Brett
I will check back.
Dave
Dave & Cris
1989 36' U280 Grand Villa SBID #3407

Re: Rear furnace not working

Reply #5 –
Dave,

To start:

Check voltage at the furnace with fan off (before turning it on) and then after turning the fan on. Compare with voltage at house battery. Low voltage means the fan is turning slower and may not generate the CFM needed to close the sail switch.

Check for any restriction in the air return or any closed vents/pinched or crushed ducts that would lower CFM.

Brett

Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Rear furnace not working

Reply #6 –
Can you swap the control boards between the furnaces? That will tell you if the control board is good or bad.
John Duld
1995 U320C SE 40'

Re: Rear furnace not working

Reply #7 –
Quote from: Gravy1159 –
Is there a gas shut off for this or is it something else? I don't think this one has ever been used.

I "googled" Atwood for the manual, but didn't find that exact model, however other models do not show a shutoff valve at the furnace.  This does not mean that one was not installed with the furnace.  If one is there, it should be the first thing the gas line is attached to. Open the outside door to see if one is there.  The door must be closed for the furnace to work.  If you are using propane for other things the main tank valve is open.  If the furnace has not been used in a long time, there could be air in the line which may take several start attempts or cracking open the connection to clear.  This is not likely though unless there are separate gas lines to each appliance, or the coach has not been used for a long time.  If this is no help follow Brett's advice.
Jerry Whiteaker former owner 96 U270  36' #4831 Austin,TX-Owner Mods LCD TV w/front cabinet rebuild - LCD TV bedroom - Dual Central AC, either can cool coach w 30 amp - Skylights at roof AC openings - Drop ceiling for ducting of AC - Shower skylight white gelcoat/wood/epoxy frame - Air Springs/Shocks replaced - 2014 CRV - 8K Home Solar - Chevy Volt

Re: Rear furnace not working

Reply #8 –
is there a micro switch that stops heater form working (as in bay door open covering vent???) I have one on mine. Check to see if it is actually connecting for the ignitor or!!
john
Coachless, now use aircraft. 2003 Ford Travelair TC280 class C. Super shape. Just for 1 yr .
1994 Ford E350 ClassC,total renovation inside and out. Now sold.
2000 U295  36' Cummins 350 c/w Banks Stinger, Resonator upgrade,Solar, LED lites.Residential fridge with slide out pantry. Build 5674. Sold
ex 92 GV 022C ored Cummins. Sold
ex 95 GV240 cat 3116. Sold
2017 Mini cooper s & 2016 land Rover LR2 HSE  LUX.
jhaygarth@aol.com    SKP #130098
treat everyone as you would like to be.

Re: Rear furnace not working

Reply #9 –
Chris Bryant probably has a manual.  Service Documents  Contact him here:  Contacting Bryant RV Services.  He will probably post it on his site for you. 
1994 U225
build #4514