Have HVAC questions? Ask an HVAC Expert for answers
Welcome to Just Answer, my name is Rick and I will do all I can to help you with your issue. First I’ll need some more info so I have a more complete picture of your situation. Please be patient it can take a few minutes for me to respond. What’s the model number of your unit?
How old is this boiler?
Where is this yellow light? On the LWCO (low water cut off)? What's the pressure on the gauge?
Yes it does have a LWCO it's part of the temp sensor. Do you know where that is?
remove sensor from well.
a. Make sure metal clip is protruding enough to come in contact with inside of well tube.
b. Check to ensure well does not have any heat transfer grease or other contaminants that may interfere with metal sensor hear contacting well.
c. If this does not resolve problem, drain boiler, remove well and examine for excessive residue build up. Clean as needed and re-install.
What is the boiler pressure???
Show me a pic of the control that has the yellow light
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You need a multimeter to troubleshoot this
You can't troubleshoot this without a meter and you need to know how to use it
You can take out the limit control. You don't have a temp sensor. That on a later version. The limit control has a copper bulb that inserts in a dry well.
If you see carbon/soot anywhere then your boiler needs to be cleaned by a pro.