How do I repair my mobile home furnace; Intertherm model E2EH-0234B, it makes the sound that it is starting up, then stops and this goes on for 4 or 5 or 6 times, and then it gives heat. I do not know where to start troubleshooting. Any help is very much appreciated. Will have to call for a service call, but hope it is something relatively simple that I can fix. Thx, Linda/Indy 10.26.2013