Suburban water heater SW6DE will not run on LP

[JPS69]

The burner will ignite momentarily and then shuts off. The furnace works fine so I think the gas flow is OK. The gas tube, burner tube and igniter are all clean. The ECO switch and T-stat reset is not popped. Could a bad T-stat cause this. The RV is only 2 years old. Any advice would be appreciated. Thanks.

[BirchyBoy]

Ours is gas only and had the same symptoms. Switch it on, the gas would turn on and the flame would start but not stay on. My money would be on the Direct Spark Ignition module. It’s a replaceable part, around $100. If you have access to the backside of the heater, it’s likely hanging loose in that area. Unplug it and look for a burned spot on the underside of the board.

[dennis45]

Originally Posted by JPS69

The burner will ignite momentarily and then shuts off. The furnace works fine so I think the gas flow is OK. The gas tube, burner tube and igniter are all clean. The ECO switch and T-stat reset is not popped. Could a bad T-stat cause this. The RV is only 2 years old. Any advice would be appreciated. Thanks.

If you remove the gas tube you will see a brass orifice in the inlet fitting. I suspect that orifice is partially blocked. Using compressed air and a soft pin such as a tooth pick, clean it up and reassemble. Be careful not to cross thread the fittings on assembly.

[MSHappyCampers]

Hi ! Welcome to IRV2! We're sure glad you joined the gang!

Like Dennis, I suspect that the orifice needs cleaning, but be sure to NOT use air pressure more than about 30-35PSI. You can permanently damage the orifice! I would try air pressure only without sticking anything in there.

Have fun and keep her between the ditches!

Good luck, happy trails, and God bless!

[Old-Biscuit]

NO.......do NOT poke anything thru opening in orifice---you will damage it
The orifice is METERED to allow X-amount of propane flow.

Soak it in alcohol to clean then blow it out....just blow on it with your mouth.

Flame proving is more then likely your issue
Flame lights off...spark electrode MUST be engulfed in flame.
Flame generates a 'electrical signal' due to ionization----this signal is used to prove flame lit so circuit board will keep DC on gas valve to hold it open.
Flame must prove it lit with in 6-8 seconds of gas valve opening

No signal..DC gets dropped...gas valve goes closed


*Issue can be spark electrode is dirty...carboned up---Clean it up with emery cloth
*Issue could be spark electrode high voltage wire to circuit board...bad wire, loose/dirty connection ---Check Continuity
*Could be spark electrode ceramic cracked...replace spark electrode
*Could be spark electrode GAP.......S/B 1/8" -- 3/16"
*Could be circuit board ----bad flame proving track.....harder to confirm unless burnt/discolored track on board

[dennis45]

Originally Posted by Old-Biscuit

NO.......do NOT poke anything thru opening in orifice---you will damage it
The orifice is METERED to allow X-amount of propane flow.

Soak it in alcohol to clean then blow it out....just blow on it with your mouth.

Flame proving is more then likely your issue
Flame lights off...spark electrode MUST be engulfed in flame.
Flame generates a 'electrical signal' due to ionization----this signal is used to prove flame lit so circuit board will keep DC on gas valve to hold it open.
Flame must prove it lit with in 6-8 seconds of gas valve opening

No signal..DC gets dropped...gas valve goes closed


*Issue can be spark electrode is dirty...carboned up---Clean it up with emery cloth
*Issue could be spark electrode high voltage wire to circuit board...bad wire, loose/dirty connection ---Check Continuity
*Could be spark electrode ceramic cracked...replace spark electrode
*Could be spark electrode GAP.......S/B 1/8" -- 3/16"
*Could be circuit board ----bad flame proving track.....harder to confirm unless burnt/discolored track on board

All due respect OB, you are the appliance guru without question,

Brass orifice, Wooden Toothpick, some compressed air. I suppose if you got real Rammy with the toothpick it could damage the orifice but with a tad of common sense, I have my doubts. IMHO,,,,,,,,

Agree, pulling the orifice out but I'd use a good shot of Brake Clean and my air line. I keep this stuff on the shelf at all times.

[Old-Biscuit]

Depends on the orifice
Brass body with laser cut ruby
Brass body with a mica insert


NO Poking ANYTHING thru that metered hole ....otherwise you can change the flow characteristics of the propane.
Just think about it.....a spiderweb can mess up the propane flow. Enlarging/scoring of the orifice will require replacement not just a cleaning


IMHO..........

[dennis45]

Originally Posted by Old-Biscuit

Depends on the orifice
Brass body with laser cut ruby
Brass body with a mica insert


NO Poking ANYTHING thru that metered hole ....otherwise you can change the flow characteristics of the propane.
Just think about it.....a spiderweb can mess up the propane flow. Enlarging/scoring of the orifice will require replacement not just a cleaning


IMHO..........

Can't argue with that [emoji106]

[Traveldude]

After a year of fooling around with a nearly new Atwood propane WH, I finally bit the bullet and put new Truma in. What a dream. Works every time. Plenty of Hot Water. Functions in cold weather and hot weather. Maybe others will work as Instant hot, but I can tell you that Truma is wonderful.

[dennis45]

Originally Posted by Traveldude

After a year of fooling around with a nearly new Atwood propane WH, I finally bit the bullet and put new Truma in. What a dream. Works every time. Plenty of Hot Water. Functions in cold weather and hot weather. Maybe others will work as Instant hot, but I can tell you that Truma is wonderful.

We have a Truma in our LTV and it works like a swiss watch. One tidbit if you don't already know, they really like to operate at 50 PSI.