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Old 11-23-2020, 03:44 PM   #1
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Suburban water heater - doesn't do anything in gas mode

I have a 4 year old SW6DE water heater. Wouldn't turn on at all the other day. Finally I shut off all switches, including the breaker, and then turned it back on, and electrical worked but gas wouldn't. It doesn't try to ignite, and I don't even hear gas start running. Is there any way to know if this is a controller or something else?

I know I have gas because furnace and stove work. Nothing else is malfunctioning inside the camper electrically, and battery was bought new this year. Reset buttons inside the water heater unit were not activated (pushed out where you could push them in). I have never replaced the anode.
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Old 11-23-2020, 04:21 PM   #2
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There are fuse links on the reset switches that need to be tested .
Info in this PDF.

Do you have a multi-meter ?
Attached Files
File Type: pdf Suburban water heater.pdf (716.3 KB, 8 views)
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Old 11-23-2020, 05:10 PM   #3
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2 years ago I bought my camper used from a dealer. It's a 2018 model and I got it in April of 2019. We checked everything out but you guessed it the hot water tank. The first time we went out I went to turn on the tank to heat up and nothing. Same tank as you have. I pulled the cover and had the wife turn on the heater. Gas went in but no igniter. I used a lighter and the gas would burn for a few seconds and go out. Called the company and talked to a technician. He said the control board was bad. Sure enough the control board was bad. It seem Suburban upgraded the board and they were failing at a higher rate than the older boards but they wouldn't replace it for free. I luckily found an older style board locally and the tank has worked every time. So it's possible the control is bad.
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Old 11-23-2020, 05:49 PM   #4
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Originally Posted by madman75 View Post
2 years ago I bought my camper used from a dealer. It's a 2018 model and I got it in April of 2019. We checked everything out but you guessed it the hot water tank. The first time we went out I went to turn on the tank to heat up and nothing. Same tank as you have. I pulled the cover and had the wife turn on the heater. Gas went in but no igniter. I used a lighter and the gas would burn for a few seconds and go out. Called the company and talked to a technician. He said the control board was bad. Sure enough the control board was bad. It seem Suburban upgraded the board and they were failing at a higher rate than the older boards but they wouldn't replace it for free. I luckily found an older style board locally and the tank has worked every time. So it's possible the control is bad.
Mine is not even opening up the gas valve...

But good to know they know the control boards are bad. I can't see what else would cause this - I'll give it a go.
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Old 11-23-2020, 05:49 PM   #5
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There are fuse links on the reset switches that need to be tested .
Info in this PDF.

Do you have a multi-meter ?
I do have a multi meter - can you direct me to the right page for the test? I'm not seeing it?

For the record, I have not touched either reset switch yet
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Old 11-23-2020, 05:57 PM   #6
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Originally Posted by patriot07 View Post
I do have a multi meter - can you direct me to the right page for the test? I'm not seeing it?

For the record, I have not touched either reset switch yet
OK , I may have posted the wrong PDF .

I'll read through this and another to figure this out.
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Old 11-23-2020, 06:29 PM   #7
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Right the other PDF is too big to post here in the forums .

The combination , t'stat/reset switch is pictured on page 14 of the pdf second item down.
To access for testing the plate with the two reset rubber push buttons must be removed . The fuse wire is visible between the two posts in the drawing.
One of the resets is 120 volt so turn off the 120 volt supply while you have the cover plate off.

Page 22 of the pdf with the diagnostic flow chart .
Shows the testing with volt meter , second box down in the center column.

" Check t'stat for 12 volts both sides of the limit switch "
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Old 11-23-2020, 10:25 PM   #8
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It's a possibility that the t-stats for the gas side is tripped. There are right there in front of you when you pull the outside cover off. You basically push them in to reset. They do go bad and have to be replaced.
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Old 11-23-2020, 10:54 PM   #9
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Suburban Water heaters use 2 sets of t-stat
One set for 120VAC electric element
One set for 12VDC propane

Upper t-stat is the High temp t-stat...manual reset via push button

Left side is for electric
Right side is for propane

In this picture the 'connector' wire between High Temp and Normal Temp is burnt into


Another issue can be with the sharp rolled edges of cut out area...wires can chaff on the edges and cause shorts


120VAC Wiring.....
CB to On/Off Switch to High T-stat/Normal T-stat to element


12VDC Wiring
DC from Fused source to On/Off Switch to Junction Box (wires are connected to water heater wiring using Wire Nuts...they come loose)
Junction box to High/Normal T-stats to Circuit Board to gas valve/spark electrode
Follow the DC circuit using Voltmeter

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Old 11-24-2020, 07:54 AM   #10
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Originally Posted by Old-Biscuit View Post
Suburban Water heaters use 2 sets of t-stat
One set for 120VAC electric element
One set for 12VDC propane

Upper t-stat is the High temp t-stat...manual reset via push button

Left side is for electric
Right side is for propane

In this picture the 'connector' wire between High Temp and Normal Temp is burnt into


Another issue can be with the sharp rolled edges of cut out area...wires can chaff on the edges and cause shorts


120VAC Wiring.....
CB to On/Off Switch to High T-stat/Normal T-stat to element


12VDC Wiring
DC from Fused source to On/Off Switch to Junction Box (wires are connected to water heater wiring using Wire Nuts...they come loose)
Junction box to High/Normal T-stats to Circuit Board to gas valve/spark electrode
Follow the DC circuit using Voltmeter

Lots of great info. I hate to ask for more help, but can you explain what the need for 2 thermostats is? Also, what is the right way to test them? Let's just focus on gas since that's what I'm having an issue with. If I follow 12VDC from the t-stat input, if I haven't had the unit on in a while, I should be getting 12VDC on the t-stat output going to the junction box, correct? Same with electric except 120VAC?

If I'm not, I can assume the t-stat is the problem. If I am, and I'm not getting 12VDC at the board output to the gas valve, then the board is the problem? Am I thinking of this right?
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Old 11-24-2020, 11:00 AM   #11
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Quote:
Originally Posted by patriot07 View Post
Lots of great info. I hate to ask for more help, but can you explain what the need for 2 thermostats is? Also, what is the right way to test them? Let's just focus on gas since that's what I'm having an issue with. If I follow 12VDC from the t-stat input, if I haven't had the unit on in a while, I should be getting 12VDC on the t-stat output going to the junction box, correct? Same with electric except 120VAC?

If I'm not, I can assume the t-stat is the problem. If I am, and I'm not getting 12VDC at the board output to the gas valve, then the board is the problem? Am I thinking of this right?
Suburban uses separate circuits for heating with AC and DC, that's why there are two sets of thermostats. The diagrams in the post show them. Atwood uses DC to power a relay that activates the AC power to the element. The DC power has a single thermostat and thermal cut-off that stops all DC to the circuit board if over heating happens, shutting off both sources of heat--AC and DC.

The T stat input comes from the J box to the Hi-limit stat and you should have 12v at the upper connector. If not, test at the J box. If not at J box, test at switch, both sides. If not there, the fuse is the final test.

If power is at the Hi-limit input, test at the lower t stat connector. If no 12 volt there, replace the Hi-limit/t stats. If there is 12 volts at the lower connector, that leaves only the connector at the module board and the board itself. Yes, you should have power at the brown wire out of the board and at the gas valve if all is working correctly. Power up to the board but not after indicates a faulty board.
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Old 11-24-2020, 11:09 AM   #12
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One , t'stat for 12 volt operation , one for 120 volt , red wires on the 12 volt , black wires on the 120.
Two t'stats easier ( less complicated ) than trying to control both voltages with a combination t'stat.

Yes following the 12 volt power flow , 12 volts through the t'stat to the control module , and no 12 volt power to the propane solenoids and no spark , your control module is bad.

EDIT: I see Larry posted while I was typing , sorry for the duplication of info.
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Old 11-24-2020, 11:18 AM   #13
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Originally Posted by patriot07
Lots of great info. I hate to ask for more help, but can you explain what the need for 2 thermostats is? Also, what is the right way to test them? Let's just focus on gas since that's what I'm having an issue with. If I follow 12VDC from the t-stat input, if I haven't had the unit on in a while, I should be getting 12VDC on the t-stat output going to the junction box, correct? Same with electric except 120VAC?

If I'm not, I can assume the t-stat is the problem. If I am, and I'm not getting 12VDC at the board output to the gas valve, then the board is the problem? Am I thinking of this right?
GAS....
12VDC to ON/Off Switch
Turn it ON...12VDC goes to Junction Box (backside of water heater tank---left side looking from rear)
Water Heater OEM wires connect to RV wires in Junction Box
12VDC goes to the Upper T-stat (High Temp set for 170*F...trips if Normal Temp T-stat fails)
12VDC goes from Upper T-stat to Lower T-stat via 'fuse wire'
(Normal T-stat set for 130*F and recloses at 100*F for reheating)
12VDC goes from Normal T-stat to Circuit Board (located on backside of Tank or near by wall of cabinet)
When circuit board get the 12VDC it then initiates Ignition Sequence (DC to Gas Valve AND Spark Electrode)

So with 'cold water'....turn gas switch ON
Follow DC circuit from switch to circuit board
Common Issues
*Fuse at DC source Blown
*Bad On/Off switch contacts
*Bad/Loose wire Nuts in Junction Box (DC on left side/AC on right side of tank looking from rear
(Tripped High Temp T-stat...means Normal T-stat failed. Try reset or replace the set)
*Burnt 'fuse wire' between upper/lower t-stat
*Bad connection/contacts on circuit board
*Bad circuit board
*Bad connections on gas valve and/or spark electrode
*Bad grounds

Follow the DC...find where is ISN'T ---that is your issue
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Old 11-24-2020, 11:42 AM   #14
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Ok, thank you so much guys! I'll report back after some more testing!
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