Suburban Furnace Problems

JeffRil wrote:
So my dad gave me his old rv that he just replaced the main board in the furnace its a Suburban model NT34 S and it seems to run fine about 3 time, then it goes to ignite the 4th time and will not ignite, fan runs, and there is spark but no fire, I have taken it apart and cleaned it all and re-thread taped all the gas lines, it is getting propane because it runs the other 3 times just fine but then wont start unless I turn the thermostat completely off and then back on again.

If anyone has any ideas or any way to point me I would really appreciate it, Thank you in advance.

Explain HOW you know it runs 3 times. How much time difference between each time it runs? IF it sparks but there is NO flame. Assuming you have a OLD NT 34 S. Odds are you have a defective Gas Valve. It is sticking. If it Sparks, the control electronics and switches WORK. That means the Sail switch and Hi limit switch function to spec. What I do when I get this model and it fails to light but DOES spark is, I hit the galvanized gas elbow where it goes into the furnace with a hammer when it sparks. That will usually make the sticking gas valve open up and then I know it is a bad gas valve. What you experiance is exactly what a sticking gas valve will allow to happen. Doug