Originally Posted by charli
I had jumpered R to G (Fan ON) and there is no voltage across white to any of the three wires. Also continuously checked on auto after flame on for more than 30 secs - no voltage. I guess the board is history. Forgot to check: but if the three amp fuse on board is burnt than i suppose there would be no power (no red light)? A stupid quest: How much and where can I buy a board in Toronto? Again thanks a lot for the reply.
I wouldn't get a board yet. Sounds like a dirty flame sensor. I don't know of any way to test the sensor, it only has one wire so there's no way to read across it. The way it works is the flame sensor is charged with AC voltage, that voltage converts to DC when it passes through a flame. Your board senses DC voltage and if it sees any DC voltage it knows there must be a flame. What tends to happen is that sensor gets dirty & doesn't pass enough voltage to the board.
And I wouldn't put much stock into your readings at the board as it looks like you aren't testing it right. Sounds to me like you're saying you jumpered R to G then checked R to G, G to W & W to R and read zero volts. That DOES NOT mean there is no voltage to those terminals. R has 24v all the time, you jumpered that to G so now G has 24v. W is the heat call from your stat being that you say it's trying to light your getting a call for heat, so W almost surely has 24v too. So I'd imagine all terminals have 24v. If you check across 2 terminals that both have 24v your meter will read 0v. The way to check is from common to all 3 terminals if you don't read 24v then you don't have power.
What I'd do is pull & clean the sensor. It's really easy & can be tried before you order parts & usually fixes gthe problem. What you're looking for is a metal rod that sticks in front of one of your burners. It should be on the opposite side as your ignitor. Usually just one screw holds it in place, remove the screw, pull out the rod brush with wire brush or something similar. Stick it back in & try relighting.