I’ve got a Southbend 436 LPG range that in the kitchen of a small market. We have ongoing problems with the oven going out. I replaced the safety switch mech a while back which made things better for a while and throw new thermocouples in it fairly often when the problem gets worse. Everything else on the unit works fine. What should I be looking at to troubleshoot? Could this model just need a new safety switch ever couple years?
Remove the pilot from the safety valve and install a adapter so you can measure the DC voltage of the thermocouple. A dirty orifice or pilot will cause it to be lower than needed to hold the valve in. It needs to remain above 10 millivolts under load. Otherwise your just guessing what's wrong. Drafts and steam will also blow it out. Like spilled boiling water. Sometimes you will find lint in the pilot air intake that makes the flame cooler because it is to rich.
I forgot to mention, most of the Southbends I've seen had a thermopile, not a thermocouple. If you have a thermocouple, they must have had a problem getting the right valve. And it will not fit right in the Southbend pilot either
As fixbear mentioned, any buildup within the pilot burner will diminish its flame quality. I suggest blowing around and then down into the pilot burner with some long and strong blasts of compressed air. That will usually sufficiently clear out anything hindering gas flow from its orifice.
Thanx's Ectofix. I'd like to add to make sure the chimney venting in the back of the oven is clear. I've seen where oven gloves and towels have dropped down into it and caused a backup of steam and moisture that corrupts the fuel mix causing the pilot to go out.
Finally got my thermocouple adapter. Right after lighting I was getting 16.2mv output and it’s been slowly dropping, now at 15.0 but still well above 10. I’ve asked the propane supplier to come test/replace the regulator in case that could be the issue as well. I’ll keep monitoring the thermocouple voltage.
It defiantly uses thermocouples and I’ve already replaced the safety valve with a new Nieco 2122, same as what was in it before.
Is the ventilation inside the back wall, I see a rectangle down inside that may have something partially blocking it. I’ll have to bring back some kind of tool to get down and clean it out.