RV Repair: furnace, gas valve, blow air

Question
QUESTION: 1987 toyota odessey.... furnace blow air but no propane to fire up...stove is on other side of heater and the stove works fine..

ANSWER: Well you may not like this answers but here we go 1st does the fan run? 2nd if you stand outside the exhaust can you 1 smell propane or hear a sparking noise. If not 3rd when the blower is on do you hear a click I know this sound goof but that click should be the gas valve. the problem you may have is parts let me know about these items and then we can dig deeper in this problem.
One last thing there is an off switch on the bottom of the t-stat it sometimes flips a different direction than what we think it has an arrow on it

let me know and then we can do more digging

---------- FOLLOW-UP ----------

QUESTION: the fan goes on...after that the clicking starts to light the propane but nothing lights and no smell of propane..& the t-stat is good..thank you

Answer
ok good not sure exactly what model we are dealing with but/ if no smell of lp then use a test light to see if  the gas valve is getting voltage to it a volt meter is better to see that you are getting about 10.5 volts or better. If you are you can try cleaning the igniter  or the part that sparks, use emory cloth or a finger nail file. dont over do it. then let me know this is alot of steps but it keeps us on track to find the problem. so bare with me

thanks let me know