I changed my filter in my central heating system and when I replaced the front the fan motor started to run. The thermostat was in the off position. I removed the front cover and replaced it again and the fan continued to run. The pilot light would not come on. It is a week later and we tried all over again to put the front back in place but the same happened. I called a repairman and he said he could not fix it as he thinks it is the relay panel and the wires are melted together. Because the unit is from 1976 a DAY & NIGHT brand he said there are no parts to be found. Any suggestions? Maybe there is something else we could check before spending $5,000 for a new unit. Being senior citizens on Social Security we'd like to get the unit fixed instead of replacing the unit.
Thanks very much.

This is just a thought, while I try to think of something better.
Are you sure that your fan switch on the thermostat is in the "Auto" position. If it is in "Run" position the fan will run constantly

P. S. Any good heating service company will have or can get most any part for that furnace.

Day and Night is still around, the same company as Carrier, Payne and Bryant. From the imformation you have provided I can't begin to guess what is wrong. Just another note, you can get a good furnace installed in almost any market for less than $5000 get bids first.

Thank you for the answers to my question. My thermostat is off and not "Auto". The repairman said it is running without being turned on because of the wires in the main relay board being melted together. I have found a few places on the internet that sell Day & Night but they are not in Texas. I did email them with my problem. I am waiting and hoping for a reply from them and maybe one of them will let me know if there is someone in my area with the parts I need. Thanks again and this is a great site. Glad I found it.