Water Heater

[GallenH]

Disclaimer. It was actually a nice trip. Cool compared to Phx. Even ran the heater one night when it dipped into the 50s.

So the Suburban water heater. Model SW6D. Worked for the first few days fine. Then suddenly wouldn't ignite. Nothing. No clicks, etc. There's a reset button on the thermostat/limiter housed beneath a rubber/plastic cover with an area to depress to reset. Only that area on the cover was cracked open. Plan to take off the cover (one screw virtually unaccessable of course) and see how the switch looks and test for continuity there. I know there's a circuit board inside under one of the beds. Does anyone know if the original Suburban board has an on-board fuse? The Dinosaur replacement does but I can't find any info on the original Suburban.

To my old eyes, those appear to be the only failure points.

Advice greatly appreciated
Glenn

[jrobe]

I have repaired my same Suburban water heater twice when it wouldn't ignite. One time I replaced the circuit / modular board with the upgraded Dinosaur board. As I recall there was a fuse on the original board but the fuse was fine when my circuit bard failed.

The second repair was to replace the gas valve assembly (part # 161109). As I recall, I could see the electrode spark at the burner orifice but there was no propane to ignite. I think there are two 12 volt solenoids in the gas assembly that activate two plungers that both have to open for propane to flow properly. These plungers weren't opening properly. The part was $50 on amazon and was easy to replace which fixed my unit. It has now been fine for several years.

I think that if there is a spark at the electrode when it starts to cycle on, this would suggest that the circuit board, the thermostat Hi-limit switch and the electrode are all probably working. You can test the thermostat assembly for 12 volts and you can check the electrode for continuity to make sure these parts are ok. Luckily, this thing is fairly easy to work on.

[GallenH]

Originally Posted by jrobe

I think that if there is a spark at the electrode when it starts to cycle on, this would suggest that the circuit board, the thermostat Hi-limit switch and the electrode are all probably working. You can test the thermostat assembly for 12 volts and you can check the electrode for continuity to make sure these parts are ok. Luckily, this thing is fairly easy to work on.

Thanks for your reply. There is no spark; just nothing. So I'll follow what you laid out above and hopefully find what's at fault.

[jrobe]

I would bet on the circuit board especially if you still have the original board which was enough of a weak link that someone designed the upgraded board. It takes about 2 min to replace the plug and play board.

[GallenH]

Tested T-limit switch this morning and it shows continuity. Tomorrow (short work days in Phx with 110º temps) I'll get to the circuit board. Make sure power is getting to board first.

[GallenH]

I did some more testing this time at the control board. I pulled the 4 wire connector off the board and tested voltage there.

SW6D Wiring.jpg

From the diagram it appears that 12v+ goes to the switch, travels to the junction box, through the T-limit switch and to the connector on the board harness/connector. Switch off = 0v. Switch on = c.13v. To me that means (1) the switch is ok. (2) the T-limit is ok. That only appears to leave the board (module) as being at fault. BTW, a while back when I cleaned the burner tube I also replaced the electrode and it's worked flawlessly since then.

So it seems like I need a new circuit board. Can anyone see anything else that it could be (before I spend c.$100 on the board)??

Thanks,
Glenn

[jrobe]

I think you did a good job troubleshooting it and that it is highly likely to be the control board. You can test the electrode for continuity across the porcelain part to the tip and also make sure the gap to the negative ground piece is about 1/8". The new control board isn't cheap but it is a lot cheaper than taking it to a repair center. Post your results after replacing it. I have no idea how someone could own a Class B without being pretty handy.