I am hoping to get back to that site tomorrow. I am fortunate that my boss isn't a jerk and knows that I am a rookie tech. He has called a local company that is owned by a former HVAC instructor at the college where I work to come and look at the units. My boss asked him and he agreed to let me be there to see what a seasoned tech finds wrong with the units. At least this way I can learn something for next time.
Well things did not go according to plan. I was called out to another job and the outside company went and did some troubleshooting. What they came back with is bad gas valves. The boss told them to change one and see if their theory was correct and if it is, then I will change the rest. If not, then back to square one.
I know it is unlikely that five valves went bad at the same time. What is possible is the site has been neglected for numerous years and the valves all didn't actually go bad at one time. Previous tech was fired for goofing off instead of working. It got so bad they put a GPS tracker on his truck and found him 45 miles away from where he was supposed to be at.
Take the magnet out of a good gas valve(When you discard an old valve or furnace) Use the old magnet as a service tool.Take the thermocouple out of the gas valve you are working on.Screw the thermocouple into the Magnet(Tester).Lite pilot hold in the magnet.See if it holds in!!!If it holds in,Thermocouple is good.May have a bad valve.Make sure you don't have an ECO.Look for 2 wires coming out of the gas valve, going to a temp switch or fusible link.An ECO will break the thermocouple MV signal,If it is open,Preventing pilot from staying lit.
If these are all old units , and or they dont have drip legs in the gas line, the pilot safety valves maybe corroded or seized up. Try tapping on the gas valve before you release the pilot knob to free them up . Worked for me numerous times.
If that doesnt work and you have 30 mv with no circuit Wires under the thermocouple, you need new gas valves.
The use of power unit(magnet from old valve) is not a conclusive test. Just because the tcouple holds the magnet only means the tcouple is producing at least 2 or 3 mv. You must use and adapter to take a load and dropout read. Usually you see around 12-15 mv under load and dropout should happen 2-3 mv. I've taken probably over a thousand mv test in my career and always used a meter. The suggestion of the power unit has merit only in a situation where you can't install the adapter into the valve due to position. I used my power unit with the adapter to check tcouple value. Of course this does not test the valve for dropout.
Wish you well
The use of power unit(magnet from old valve) is not a conclusive test. Just because the tcouple holds the magnet only means the tcouple is producing at least 2 or 3 mv. You must use and adapter to take a load and dropout read. Usually you see around 12-15 mv under load and dropout should happen 2-3 mv. I've taken probably over a thousand mv test in my career and always used a meter. The suggestion of the power unit has merit only in a situation where you can't install the adapter into the valve due to position. I used my power unit with the adapter to check tcouple value. Of course this does not test the valve for dropout.
Wish you well
Maybe it's just a difference in terminology, so I'll ask...
What are you referring to as a "power unit?" Can you post a link?
[Avatar photo from a Florida training accident. Everyone walked away.] 2 Tim 3:16-17
Maybe it's just a difference in terminology, so I'll ask...
What are you referring to as a "power unit?" Can you post a link?
Hi TM
Years ago when you could actually purchase sections of gas valves one was the magnet. It was termed "power unit" by Honeywell as well as other mfg.
I don't have link to post
Magnet has always been the accepted term.
Possibly it would be the same as saying Freon when speaking of refrigerants?
I know its a long shot, but have you tried blowing out the pilot tubing and carefully inspecting the pilot orfice? Sometimes spiders will lay eggs inside the tubing, its not enough to stop the gas flow but enough to weaken the pilot and make you rip your hair out....
When I was a young tech I learned this after a couple call backs and was stubborn thinking that if the pilot is lit and how the hell would a spider get inside that tiny tube - but they do....
BTW, you have to use compressed air, simply blowing on the tube will not do it...
Originally Posted by Fender60
Reply
