20 year old gas forced hot air furnace pilotless located in utility room off master bedroom.works great until temp outside drops to 20 or below.can hear unit trying to fire through a series of clicks and clunks but no fire.after 5 attempts to ignite fan starts and runs continuously.I'm guessing the pilot system gets too cold to light. Any suggestions? Found more info as requested. Built in 1983 cdc60 1.5 bip. 60,000 BTU natural gas.made by dornbach furance & foundry.pilot system is honeywell intermittent pilot 100 percent shutoff. Also,when furnace failed to light last night,I used a small electric space heater to warm burner area for ten minutes or so then repowered furnace. Unit fired up normally and gave good heat.?

Brand and model number of furnace?
Is this LP or natural gas?

20 year old gas forced hot air furnace pilotless located in utility room off master bedroom.works great until temp outside drops to 20 or below.can hear unit trying to fire through a series of clicks and clunks but no fire.after 5 attempts to ignite fan starts and runs continously.i'm guessing the pilot system gets too cold to light. any suggestions? found more info as requested. built in 1983 cdc60 1.5 bip. 60,000 btu natural gas.made by dornbach furance & foundry.pilot system is honeywell intermittent pilot 100 percent shutoff. Also,when furnace failed to light last night,I used a small electric space heater to warm burner area for ten minutes or so then repowered furnace. Unit fired up normally and gave good heat. ??
Very carefully try to clean out the pilot assembly. You may have built up some spent carbon all along the surface to the pilot oriface. Take some steel wool or sand paper to the spark rod and pilot housing. Also check that your ground wire coming from the pilot assemble has a good connection. You may also be condensating a bit of moisture. You may not have heated everything up to start but just made it nice and dry. Good Luck