Old coleman 220j195 not lighting. there is gas. mantles are hlfway corroded but still white. pressure valve is working will not light.

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: pilot light won't stay lit after release of gas valve.tried few t

Most likely it's time to replace the thermocouple, the safety device that makes sure the pilot is lit. New thermocouples are cheap and you can find them at most hardware stores and the big-box places (Home Depot, etc.)

Here is a site with basic information to get you going.

SOURCE: pilot will light but main burner will not light

if burner lights after jumping valve you have something wrong in thermostat loop. disconnect the 2 thermostat wires on gas valve and use multimeter on continuity setting. if all wires ,connectors and components are good,you will get a tone.since you have jumped out each component in thermostat loop with no success ,i would suspect a bad wire or oxidation on a terminal .

SOURCE: i want to know how i light and use my Coleman

fill the tank about 2/3 full. put the cap on tight, pump the air pump about 50 to 75 times to pressurize the fuel tank, you may have to turn the pump knob in a few turns to get a good pressure feel when you are pumping, then push the pump down all the way and turn the knob in until it gets snug. then you turn the gas knob on until you hear a hissing noise. turn it off and stick a large lit match in thru one of the holes in the steel plate below the lens and hold it close to one of the mantles then turn the gas on again and it should light up. let it run for a minute or so until the mantles light up brightly and then turn it on the rest of the way. I've done this hundreds of times. hope this helps and good luck. Jeepfxr

SOURCE: My coleman floor furnace will not stay on

Have the thermocouple replaced, ensure the pilot flame is blue - not yellow, yellow indicates blockage in pilot