Water Heater, Stove, and Oven all work in my 73. However; the Coleman heater will not light. Does anyone have a suggestion as to where to start troubleshooting this?

Check the gas supply tube to the pilot and make sure its not crimped, or has a hole worn through it. On my 1969 Bon Voyage, this tube is aluminum, and had been installed in such a way that it rubbed against the access door, eventually wearing a pin hole at a bend point (this took 20 years). The hole was hidden from obvious view and it took a while to figure out the problem, but the hole kept gas from getting to the pilot, preventing it from lighting. Hah, the hole was so small I was able to do a field repair with duct tape until we got home! Another potential problem could be that the thermal bulb has gone bad... keeping the pilot from lighting. Both the aluminum tube and bulb assembly can be found at vintage trailer supply sources. Good luck!

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1967 17' Hi-Lo Bon Voyage (1967-1969)
1969 19' Hi-Lo Bon Voyage (1969-2011)
2004 27' Hi-Lo TowLite (2010-present)
2007 Chevy Suburban

When I used to work on them I found about 50% of the time The problem was caused by a dirt dober making a nest in the burner chamber. To repair requires a disambley of the furnace. One you clean it out I suggest you use a dober screen on the exaust. They can be bought a most trailer parts store's
Sam

So what you are suggesting, Sam, is to complety take the furnace apart? I am ok with that... just making sure that is your recommendation.

JM, by 'Themal Bub' do you mean 'thermocouple'? I will be checking the pilot supply tube soon. I already had the connector off and got it cleaned out.

This is a major problem in Louisiana. I do not know if you have this problem, but it would be worth exploring. As you look for the dirt dober nest you have a chance to find the problem even if the burner chamber or squral cage are not full of mud. Eather way you have a 90 percent chance of finding and fixing the problem.
Sam

there is evidence of what we call here in Kansas Mud Dobbers. Entomology taught me they are Vespid Wasps.

Mainly, I just wanted to be able to tell my wife there was a perfectly good reason for me to disassemble the heater!

Try this first-- If your pilot will not light or barely burns... take the supply tube off and soak in rubbing alcohol for 24 hrs, chances are the orifice is clogged. But above all DO NOT force anything even a small wire down the orifice. Worked for me on an old 77 Apache furnace.

Heath,
Yes, thermocouple.

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1967 17' Hi-Lo Bon Voyage (1967-1969)
1969 19' Hi-Lo Bon Voyage (1969-2011)
2004 27' Hi-Lo TowLite (2010-present)
2007 Chevy Suburban

Should I worry at all about the valve? While I have it out is there anything I should do to it? It doesn't look promising in regards to replacing it....

The Valve is most definitely NOT working. I called a friend in heating and air conditioning, and it so happens they are a Coleman dealer! So I am crossing my fingers....I'll let you know.