Have a 1950's Ward model 5700 Floor furnace that has been giving some trouble over the years. House was built in 1950 in Los Angeles County along the foot hills At first it would not light unless the T-stat was set 15-20 deg higher than the current temp. Would fire up if the two wires were jumped to make contact and over all worked as needed but of course with the temp set higher than needed would get a little to too toasty on some nights. This week, could not get a response from the furnace, so jumped the wires and it would ignite. The old T-Stat had been replaced about 12 years ago, but was looking a little beat up and since it had been giving problems for the last few years, figured it was time to replace. Installed new one and set the temp and furnace ignited with in a seconds. Figured the problem was solved. Today I noticed that someone had turned the T-Stat all the way up and was not lighting. moved the T-stat through the range a couple of times but no ignition. Pulled the T-stat from the wall to check the wiring, and got the furnace to ignite. Cycled the T-stat 2-3 times and it seemed to work. I re-installed the T-stat on the wall. Went to cycle the T-Stat to ignite again and no dice..... Pulled the T-stat off the wall yet again and checked every thing, but still no fire. I jumped the wires and was able to get the furnace to ignite. Jumped a second time and no fire. A couple of more tries, ignition and has been intermittent (however slight) with a direct jump. I fear that the valve is shot. Where to find replacement gas valve for such an old beast? Thanks in advance for any help anyone can provide.

I have a Trane XL 80 system. When I try to start up the system it shows normal heat call on the circuit board. I ignites about six times in bursts of 10 to 15 seconds. Then the ignition turns off and the blower starts with no heat. The Circuit board then flashes in two light bursts. The error code says that the system is locked out check polarity. Not sure where I should be checking. I have an White Rodgers 50a50 473 Circuit board.