norcold n821 won't stay lit

Thanks for the thorough responses. I have done all that has been advised to the spark electrode. Unfortunately it hasn't improved the situation. I have ordered a new electrode for 12 dollars In hopes I have some how missed something. At worse, I have a spare electrode. At best, it fixes it. I am truly thankful for all the help I have received.

You have a spark electrode........electronic ignition---no pilot flame.

When the thermostat calls for heat....high voltage is sent thru spark electrode creating the ignition spark & voltage is sent to main gas valve opening it.
Power is held on gas valve and spark electrode for 7-8 seconds to allow for main flame to light. After main flame lights a milivolt signal is generated via flame ionization. This generated signal is sent back to main circuit board to 'prove' main flame is lit. The spark electrode is the path for this signal.
When circuit board gets 'proof' it holds voltage on main gas valve keeping it open until t-stat setting is satisfied.

You have good spark, main flame lights off BUT is not being proven....
Could be spark electrode is dirty (milivolt signal can't be generated), could be cracked ceramic (milivolt signal is going to ground), bad/dirty connection on high tension wire from electrode to board (milivolt signal can't pass) or bad circuit on board.

Clean up electrode with some emery cloth, make sure electrode is engulfed in main flame, check ceramic for cracks/tracking, clean up connections on high tension wire and wipe it down with a rag sprayed with silicone.

Still not staying lit......board.

You can have board tested at an RV Repair.

If you need a new board..get a Dinosaur Board LINK

Gas Valves never fail(yes, I know) but they rarely fail
The usual cause of your problem is the Spark Electrode and/or the wire it connects too. Some models the Spark Electrode comes with the wire. I believe your model does. There is enough voltage to Spark, but because of a defective porcelain mount or leakage in the wire the millivolt return flame signal cannot make it to the board. RARELY does a board cause this problem. Doug

That's a great explanation of the difference between thermal couple and flame sensor. Thank you. Unfortunately that makes me lean even further to this being a board issue. The trouble shooting guide says to change the board but I don't want to invest 170 dollars until I check all possible causes. You have been very helpful.

A thermocouple when heated with a flame, in this case pilot light, produces 250 millivolts which energizes a coil that holds the pilot valve open.
Flame Senser. Fire/flame will conduct electric. The Flame Senser is nothing more than an ohm meter, so if there is continuity through the flame then the burner valve is held open.

Dusty

Thanks guys. I appreciate the quick responses. My burner has been thoroughly cleaned and I'm certain my meter is not that accurate as well. Thanks again

If you are getting Fs, then the first suspect is soot all over the burner where the flame slots are. You take off the cover and clean it all out and bang/tap on the chimney to make sure you got all the loose soot.

Is your manual like this one from Chris Bryant?

I ask because this is a link to actual factory manuals.

I really don't want to offer a suggestion because it's become apparent I don't understand the difference between a Thermocouple and a Flame Sensor. Since I believe the N-Series uses FS, not sure I can help with the troubleshooting.

But I will say that I doubt your meter is accurate enough in ohms for that 0.5 difference to disqualify the valve.

We've got some good tech people here. Be patient and you'll get some help.