Suburban Heater Problem Columbus 389FL

[runningbubba19]

I'm new to the forum.
We have a 2018Columbus 389FL and we are having problems with our Suburban SFV-35Q heater. I am a HVAC Tech. I'm relatively sure it's the igniter or gas valve. It goes thru the 3 trial sequences to light the burner then locks out and shuts off after the 3 minute cycle. Does anyone know how to access the rear side of the heater on this particular model to unhook the ducts? The way this model (Fifth Wheel) is built it looks a little tricky. Any help would be greatly appreciated. I think I need to heater thru the side of the compartment where the auto-leveling control is located and I may need to cut the wall panel.

[Capacitor]

Remove igniter and use emery cloth or coarse sandpaper to clean both tips first.

[runningbubba19]

Thanks for the Info. I know how to clean the igniter.
I need info on removing the heating unit from the fifth wheel

[runningbubba19]

Originally Posted by Capacitor

Remove igniter and use emery cloth or coarse sandpaper to clean both tips first.

I figured out how to remove heater from fifth wheel.
I also noticed that when the heater comes on that it goes thru the 15 second purge and 7-8 second igniting attempt. I can hear the relay kick in on each of the 3 attempts but I don't smell any propane at the burner air exhaust outlet. Could the gas valve or the relay on the board be defective?

[rwhit]

Do you hear the electronic ignighter clicking or just the relay click?

[not2yzsr]

I have a rk 346 5th wheel that had the same issue. I changed the sail switch and high temp. No luck . I put in a Dinosaur control board and all is working.
My problem was getting to the furnace. No access to the furnace. I found taking out my electric fire place and shelf then cutting a whole along the panel seam gave good (not great) access. I should have taken pictures but did not. I hope this helps.
From the hole i had easy access and pulled the furnace out for repair.

[MR.M]

Originally Posted by runningbubba19

I figured out how to remove heater from fifth wheel.
I also noticed that when the heater comes on that it goes thru the 15 second purge and 7-8 second igniting attempt. I can hear the relay kick in on each of the 3 attempts but I don't smell any propane at the burner air exhaust outlet. Could the gas valve or the relay on the board be defective?

If it's going through the ignition sequence but smell no gas from the exhaust . test to 12 volt at gas valve . my guess is a new board , the Gas valves rarely go out . make sure you have propane on and full . if the sail switch was bad or not making contact it would not start the ignition sequence . If you don't have an out side access panel then you should be able to access from panel in pas through. If you have an outside access then just one screw holds the whole assembly in, bottom center below blower is the screw .

[AntonJ]

Sounds like the problem I had when it was the propane regulator. I am not a tech.

[dahagen]

Originally Posted by not2yzsr

I have a rk 346 5th wheel that had the same issue. I changed the sail switch and high temp. No luck . I put in a Dinosaur control board and all is working.
My problem was getting to the furnace. No access to the furnace. I found taking out my electric fire place and shelf then cutting a whole along the panel seam gave good (not great) access. I should have taken pictures but did not. I hope this helps.
From the hole i had easy access and pulled the furnace out for repair.

X2

[runningbubba19]

Originally Posted by MR.M

If it's going through the ignition sequence but smell no gas from the exhaust . test to 12 volt at gas valve . my guess is a new board , the Gas valves rarely go out . make sure you have propane on and full . if the sail switch was bad or not making contact it would not start the ignition sequence . If you don't have an out side access panel then you should be able to access from panel in pas through. If you have an outside access then just one screw holds the whole assembly in, bottom center below blower is the screw .

It sounds like the gas valve is clicking on but I can't hear the igniter clicking. It goes thru the 3 sequences trying to heat. I can't smell any propane in the burner exhaust outlet when the valve clicks. I have plenty of propane and good pressure. Heater eventually locks out cause burner does not light.

[MR.M]

Originally Posted by runningbubba19

It sounds like the gas valve is clicking on but I can't hear the igniter clicking. It goes thru the 3 sequences trying to heat. I can't smell any propane in the burner exhaust outlet when the valve clicks. I have plenty of propane and good pressure. Heater eventually locks out cause burner does not light.

did you verify 12 volts to the gas valve . the gas valve will click but it should not be clicking , if you have spark , you can test at the board and if you get 12 volts to the gas valve then most likely it's the board . you did say you were a hvac tech right ?

[Larry-NC]

Originally Posted by AntonJ

Sounds like the problem I had when it was the propane regulator. I am not a tech.

This ^^^^^^^

The regulators fail after 8-10 years, and the outlet pressure begins to rise. The Suburban furnaces are VERY picky. They need 11" water column (w.c., about 1/2 psi). At 14 ", they will refuse to ignite, even though the range and water heater work fine.

Of course, if you smell no propane at all at the exhaust port, this is not the problem.

[runningbubba19]

Originally Posted by Larry-NC

This ^^^^^^^

The regulators fail after 8-10 years, and the outlet pressure begins to rise. The Suburban furnaces are VERY picky. They need 11" water column (w.c., about 1/2 psi). At 14 ", they will refuse to ignite, even though the range and water heater work fine.

Of course, if you smell no propane at all at the exhaust port, this is not the problem.

Should I test the gas valve while I have removed heater from fifth wheel. I can hook it to the propane line and 12 volt battery just to verify valve is opening?

[rwhit]

Have you checked the high limit with an ohm meter? If you have continuity across it then I would check for continuity across the airflow switch while the inducer motor is running. Both of these switches will keep the gas valve from opening. Do not in any way jump out these safeties. LP gas is not forgiving at all
Replace them if they are bad. My unit has a schematic but not sure yours is the same so if both of these switches test good you will have to find the power wire going to the gas valve and see if it gets a signal.

[MR.M]

Originally Posted by rwhit

Have you checked the high limit with an ohm meter? If you have continuity across it then I would check for continuity across the airflow switch while the inducer motor is running. Both of these switches will keep the gas valve from opening.

That would also prevent it from starting the ignition sequence . so if you can hear it sparking then both of those would be good .

[runningbubba19]

Originally Posted by MR.M

That would also prevent it from starting the ignition sequence . so if you can hear it sparking then both of those would be good .

The high limit ohm's out good and sail switch is good goes thru 3 ignite sequences then locks out. Relay on board clicks on each ignition sequence no sparking and no gas smell in exhaust outlet during all 3 sequences. Should I test the gas valve since I have the furnace out of trailer. Will it still spark if gas valve doesn't open. Cause I can't hear it sparking on any of the sequences?

[runningbubba19]

Originally Posted by runningbubba19

The high limit ohm's out good and sail switch is good goes thru 3 ignite sequences then locks out. Relay on board clicks on each ignition sequence no sparking and no gas smell in exhaust outlet during all 3 sequences. Should I test the gas valve since I have the furnace out of trailer. Will it still spark if gas valve doesn't open. Cause I can't hear it sparking on any of the sequences?

I believe it is the control board also I think I'm gonna replace the igniter while it is open.
The igniter looks ok but they are not that expensive

[rwhit]

I've been doing commercial HVAC since 1982 and on LP applications it starts sparking before it opens the gas valve, so yes it will spark. How did you test the sail switch?

[rwhit]

If the ohm meter said it closed its between your gas valve or your control board. On my brother in laws trailer I could a mud wasp nest in the chamber that was blocking air flow thru it and it would not make the sail switch.

[rwhit]

Good luck let us know what happens.