Our Jr had an issue with Air flow last year and before cold weather set in I opened it up and cleaned the heat exchanger. The right side was completely plugged with carbon the left side was open and clean. I took it out to the garage and made a cardboard cover with a hole in it for my shopvac then blew out the unit. The carbon was loosely attached and came of easy. I reassembled the unit and hung it back on the wall.
Now only the right side of the flame bed works. The right side gas valve seems not to be opening. I measure about 600 ohms on the coil and see the voltage swing when it is calling to open and nothing. Opened the unit back up a pushed lightly on the plunger and it is free and about the same spring Resistance as the on the right. (!!!Dangerous!!!!) I held my finger over the right side hole and waited for the left gas valve to open it did not.(don't try this unless you are sure you know what to expect)
I can not see the voltage because my fluke will not stabilize before it turns off I suppose I could use a small light bulb.
What do you think? Strange .........
I believe the valve is controlled by one of the relays next to its circuit board plug but that must be working as the voltage changes. Next? maybe apply voltage from out side to see if it opens?