Low Burner Flame - Coleman 4312 Furnace

[Walkintree]

Hey all!

I have an older camper (1983 to be exact) which I got for a very good price... I've been fixing it up slowly, and my biggest obstacle currently is the furnace. After redoing some of the electrical I got it running, however after my first night using the camper, it no longer puts out much heat. Observing the furnace I found:
-The pilot lights and stays lit.
-The blower comes on after about five minutes of having the thermostat turned all the way up. And comes on about once every ten minutes or so.
-The burner can be seen, but the flames are only 1/4 - 1/2 inch high, though a nice blue color.

So far I've tried replacing the main propane regulator to no effect. I'm unfamiliar with how these work, and everything I've been able to research seems to suggest I should have NO flame, or NO blower... Not somewhere in between! Any suggestions are welcome!

[calindor]

I am trying to recall if I ever took note of the flame height and I'm afraid that I never paid close enough attention until the thermocouple needed replacing... and then I took it out for the renovation. Sorry!

I posted the installation and operating manual for this furnace a few years ago, check it out. Look for the 2 Coleman 4312 ST-200 links.

There are some troubleshooting tips in there as well as lots of other info. It describes the main burner flame as being blue with slight yellow tips being acceptable, but doesn't mention flame height.

Fiberglass RV - Document Center - Furnaces/Heaters

Clayton

[Walkintree]

Thanks Clayton, I will check there for info! I appreciate it.

[Gilles]

You can download both books "Installation" and "repair", in pdf format from this link :

TheSamba.com :: Coleman Furnace 4312 - Installation and Operations Manuals

But when it is a problem of gas, I always prefer to visit a qualified person.

[Walkintree]

Thanks for the references guys. Unfortunately neither one seems to indicate what my problem could be. There's a service manual out there as well, but every copy I've found is incomplete, and stops one page short of "Table 5". This, of course, being the table that would be most likely to have my issue and potential solutions in it.

I'm off at work for a week or two, but in suspecting my thermostat. Once I'm home I'm going to attempt wiring the positive and negative together (simulating a thermostat cranked right up) and see what happens. I'm thinking if my furnace fires right up the thermostat is cooked. If it remains the same... Well I'm back at square one.

If anyone sees a problem with my theory please point it out! I'm slowly coming to my wits end with this furnace.

[Bob Miller]

Thermostats are just an ON/OFF switch, either it works or it doesn't. With just two wires there wouldn't be any flame control anyway.


BUT Does it blow out hot air is the real question...??


If anything I would suspect a gas valve that isn't opening completely, at that age it should be no surprise.

[Bob in Mb]

This past weekend I had a similar problem but it affected all my propane appliances - very low flame on stove , poor fridge performance . Upon investigation on the net I discovered that propane regulators have a safety feature which restricts flow if a leak is detected , however this saftey device is sometimes fooled . Example - if the valve at the tank is turned off before an appliance is turned completely off , the next time it is used it will detect a leak , or if the tank is full and the valve is turned on quickly and full it detects an imbalance and restricts the flow . In either case the regulator will have to be reset before it will operate properly .
To reset regulator -
1] Turn off all appliances fully
2] Turn off valve at the tank
3] Disconect supply hose at the tank - wait about 2 minutes - the regulator will reset
4] Reconect supply hose at tank
5] Turn on valve at the tank SLOWLY about two turns only
6] Re-ignite appliances as normal

This procedure solved my problem , of course if there were a leak somewhere the problem would continue and need to be located and repaired .