Suburban Furnace SF 35 Problems

[2seniors]

I have pulled my furnace out and checked that the igniter is working , fan is running and I checked to see if the orifice was clear, it was, I think the problem is that it's not getting propane, When I took off the propane connection I could smell the propane but it isn't getting to the igniter,everything is very clean . any suggestions? It's in a 2003 Rexhall Aerbus

[Old-Biscuit]

DO other propane appliances work....Stove top burners, water heater???


Could be furnace gas valve solenoid bad....
*check that it is getting 12V DC at same time ignitor is sparking (gas valve only has power for 6-8 seconds during ignition cycle)
*gets 12V DC then check resistance on solenoid....should be 40-50 ohms


Could be lack of gas flow....if furnace hasn't been used in a while the ignition cycle may take several attempts before full propane flow is established (only 0.4 psi in system) 5-6 attempts common...then should light off w/o issue


Could be bad LP Reg....low system pressure
11"WC is 0.4 psi
9" WC is 0.32 psi
Can NOT visually tell that system is 0.08 psi low....have to measure using a manometer

[Bucky573]

Originally Posted by 2seniors

I have pulled my furnace out and checked that the igniter is working , fan is running and I checked to see if the orifice was clear, it was, I think the problem is that it's not getting propane, When I took off the propane connection I could smell the propane but it isn't getting to the igniter,everything is very clean . any suggestions? It's in a 2003 Rexhall Aerbus

Go here and download this manual. There is a troubleshooting guide that will walk you through steps to isolate the problem.
I used it on a friends furnace last week to find a faulty limit switch.
http://www.bdub.net/manuals/Suburban_Service_Manual.pdf

[Old-Biscuit]

Troubleshooting guides & service manuals are very helpful




OP posted some clues that narrow troubleshooting down to gas valve circuit

Fan runs....spark electrode fires (Sparks)
That means furnace has DC power.......Sail Switch/High Temp Limit switch are closed (only way for DC to get to circuit bd)


Issue is with gas valve
No DC from circuit bd...bad connection/contact or bad circuit bd
Is getting DC from circuit bd.....bad solenoid(s)


Everything else is working.....so gas valve is issue (provided propane is working for other appliances)

[2seniors]

Originally Posted by Old-Biscuit

DO other propane appliances work....Stove top burners, water heater???


Could be furnace gas valve solenoid bad....
*check that it is getting 12V DC at same time ignitor is sparking (gas valve only has power for 6-8 seconds during ignition cycle)
*gets 12V DC then check resistance on solenoid....should be 40-50 ohms


Could be lack of gas flow....if furnace hasn't been used in a while the ignition cycle may take several attempts before full propane flow is established (only 0.4 psi in system) 5-6 attempts common...then should light off w/o issue


Could be bad LP Reg....low system pressure
11"WC is 0.4 psi
9" WC is 0.32 psi
Can NOT visually tell that system is 0.08 psi low....have to measure using a manometer

I did get 12V and I heard a click, was that the valve opening? All I did was clean the connections

[Old-Biscuit]

Originally Posted by 2seniors

I did get 12V and I heard a click, was that the valve opening? All I did was clean the connections

YES....
Solenoids 'click' 'clunk' make noise when getting energized


Dirty/loose connections will STOP 12V DC