I have an older Coleman in wall propane furnace, Model 2343.

SOURCE: How to install an igniter?

if the heater uses a hot surface igniter its a simple matter of unscrewing the igniter and replacing it with another unit. if it is a spark ignition, the spark wire is a heavy insulated wire that goes to the gap. check out white-rodgers for a replacement. if your furnace uses a purge mode get a purge cycle programmable igniter.

SOURCE: Coleman forced air furnace blower

Rmove the two screws holding the blower in place and slide it out. With the power off, rotate the wheel and inspect for debris or an impingement. If everything turns easy, you have a bad motor or start capacitor. If you have rubbing, adjust the wheel. If the motor will not turn, replace it.

SOURCE: Coleman Propane Furnace Good pilot light but feed/ignite main burner

If you have a volt ohm meter take the two leads off the gas valve and ohm out the connection should have resistance for the coil. You said you have 12 volts from the thermostat white and red in the heating mode you should have minimum 26 volts. If you want to check the transformer should have 28 volts. Almost sounding like the transformer is getting weak. You can get parts for a 20 year old unit at any HVAC parts house. Try Washer Specialties here in Wichita Kansas they are on the web. Lowes even carries Transformers. Has to be rated 120 volt primary side secondary side 24 volts and 40 VAC.

SOURCE: I have a Coleman furnace model number 7681-8171/b.

Short of being able to look at everything Its impossible to say exactly what the trouble is. Does the board have a blink code showing and a legend that says what this is? What fuel are you on NG or LP? What does the flame look like (if you can see it) IE a lot of yellow, Some orange and Blue...?. Did anyone else look at the system and the thermostat? Does it have AC or HP on it too?

The only 1 thing I may be able to offer is this. On your thermostat (if it is not electronic) there is a needle pointer that points to a number it should be around .4 to .7 if set to a lower number the thermostat will cut the unit off well before it completes a heat cycle.

Mark

• 704 Answers
• Posted on Aug 06, 2009

SOURCE: manual on how to clean Coleman furnace model #

Here's a web link to the Technical Manual for your furnance. This should contain all the tech specs for your unit.

http://www.winfieldsupply.com/images/HVAC/dfahtechguide.pdf

Also, please give Coleman customer service a call at 1-877-726-5362 to obtain a Owner's Manual for your particular unit, which should contain the periodic service schedule for your furnance. Here's a link to the Coleman site with maintenance tips for your furnance.

http://www.colemanac.com/homeowners/maintenance_tips.asp?prodLine=1&ProdID=0

Hope you found this info helpful and best regards!