I have one furnace in my 36', mounted just above the bay with the lift up door. When the door is lifted the furnace shuts off because the door blocks the exhaust. The furnace started acting freaky a few weeks back, comes on the the burner lights, then goes off, does that three times, then shuts down. The code says it isn't seeing ignition, so I pulled the board, took it to my local RV shop with a tester, they charged .5hrs ($60, new board on the internet was less than $100) said the board was ok. Put the board back, still shutting down. Later, got something out of the bay, slammed the door, the furnace started, worked fine till today. Same issue, tried the door, no change. I detect no voltage on the door micro switch, ,,should there be on one side ?
Sounds like the micro sw might be getting wiggie. I haven't checked but I would imagine it is in the ground circuit. I have bent mine a time or two and had it do that.
Must be a normally open switch... just put a jumper across the switch until you can get a new one (assuming it is faulty and not just maladjusted in relationship to the closed hatch) and the furnace should stay on. Just make sure that you don't leave the hatch open while the furnace is running or even set to come on with the thermostat.
Don
My guess is there's something else amiss, other than the door safety switch, as I would think any of the safety switches would close the gas valve and halt ignition attempts. Check to see if the flame proving device or thermocouple is loose, or dirty. Three strikes and your out is pretty common on burners, and they typically have a timer of 15 minutes or so to allow unignighted vapors to vent. If it has draft inducer fan they a diaphragm pressure switch that is a common failure point.
I would think a door switch would lock out any startup.
Sequence of operation is
signal from t stat sends power to board
Draft inducer fan starts and runs closing sail switch, this tells board you have draft.
Board starts igniter, clicking sound gas valve opens if no flame is sensed by thermocouple gas shuts off.draft fan runs system will try a nd light 3 times then lock out.
Early boards locked out after 1 try. Dinasour boards give you 3 trys.
Sounds like the igniter wire is bad.
The furnace is igniting, no doubt about that, it does it 3 times, just as the troubleshooting outlines for the factory furnace (board). I'm focused on the microswitch, or its wiring, because of that one past incident.
Can you get to the connections for the sail sw? By pass it to test the furnace.
I'm not sure if it would lite if the sail sw was the problem or if it would shut down the furnace after ignition.
If sail switch does not close (indicating adequate air flow) then furnace will not attempt ignition. Problem is elsewhere.
The door micro switch probably just completes a ground circuit when closed - hence, no voltage on either contact.
I think Old phart phred is on the right track. It lights, but doesn't stay lit. Bad thermocouple?
If the burner is lighting but then shutting down you have a problem with the flame sensor .flame has to be sensed in order for control board to keep gas valve energized.clean sensor tip with emory cloth or something snd wiggle clean wire end terminals
There are two different setups for sensing the flame. Depending on furnace model, thermocouple may be built into the ignitor (local sense), or it may be a separate piece (remote sense). See diagrams in manual linked below:
http://bryantrv.com/docs2/docs/hflamefurn04.pdf
This.
Step 1, rule out micrositch cicuit by jumping it.
step 2 check flame sense circuit (find a manual).
Remember, it used to work and stopped....can't be too complicated.
The thermostat calls for heat,the blower comes on, sail switch closes, ingniter comes on,gas valve opens, gas ignites, igniter and it's wire become the flame sensor to the board to let it know that all is working, if you have no flame it will shut down, if you have a flame
and it shuts down it could be a bad igniter or a bad igniter wire.
To cold to mess with it today, leaving on a cruise in the morning. Think I'll wait till it warms up....then I won't need it !!
Hope this helps: I've been having problems with my rear Hydro Flame (Attwood) furnace for a while: it would fire, then not, on and on. My VOM got a huge workout, everything seemed to be getting juice. Cleaned the terminals, no help. O.K. new board time. Had a new Dinosaur board, a "Universal" spare for the front Attwood, installed it, same deal. Went to the dark side and figured it was the igniter. Now, I've had furnaces for thirty years and it was almost ALWAYS the board, so something just did not make sense. Before pulling the furnace, I called Dinosaur and explained the problem, giving them the model # & year of the furnace. They checked, and sent me another board, which I installed just now. Fan came on, red light on the board, heard igniter "click" once and, BINGO, green light and heat! Moral? Make sure Dinosaur (who I like) knows what you're installing it in! ^.^d Fingers crossed.
Ditto here. New Dino board, intermittent ignition gone.