Duo-Therm 11HLU gravity furnace Dec 18, 2020 14:07:35 GMT -8
Post by haze5736 on Dec 18, 2020 14:07:35 GMT -8
I wanted to share my experience repairing a Duo-Therm 11HLU gravity furnace. There was not a lot of information out there, so hopefully this will help someone else down the line.
My furnace still worked with the exception of the thermostat. So I could light the furnace and it would come on but I could not regulate the temperature. It was either on or off. There was no longer any resistance when turning the thermostat and no longer that distinctive click when going from off to a setting that would command heat. We don't camp in extreme cold so we were turning it on before bed to get the camper warm then shut it off at bed time hoping to make it through the night. If it was really cold (30F or just under) I would wake up in the middle of the night, cold, and would run it for a short time.
My original gas valve has an identifier on it, TV17AA10. I didn't know this when I was researching because at that point I had not removed the original gas valve to be able to see it. I believe I found something on the Robertshaw website that said this original number crossed to a Robertshaw 710-201. I originally found this out after hours of searching the web. I found a Duo-Therm document that showed the original gas valve part number of 41-0640. I can't remember the site but one crossed this number to the Robertshaw 710-201.
The instructions that came with the replacement valve noted that a conversion kit was required for LP use. That part number is 1751-013. Although, the part number on the box I received is 1751-01C. The ebay listing did advertise it as a 1751-013.
Two of the ports on the new gas valve are in different locations so some tubing bending was required. The pilot gas line and the thermo-couple line needed to be gently manipulated. Luckily the length on both tubes was ok to reach the new locations. The pilot gas line needed to be bent 90 degrees in the opposite direction as well as curved to meet the new location. I had to work very slow and careful to avoid kinking or breaking the tube.
I finished by purging the air out of the system then used soapy water to look for leaks. And ,of course, my inlet was leaking so a couple slight turns of the nut and no more leaks.
The hardest part of the whole process was the research.