The dispatcher calls Bob on a cold morning and explains that a customer's oil furnace will not fire on a regular basis. The customer related that the furnace would start sometimes and sometimes it would not, and he would have to reset the primary control. Bob asks for the customer's phone number, calls, and gets the homeowner's wife and tells her not to reset the furnace until he gets there, within the hour.
When Bob arrives, the wife tells him that she had not reset the control again. He asks her when the burner had been serviced last and she says about two years.