I have a Burnahm oil burner that is vented through a side wall via a Tjernlund venting system. The entire unit is only about 12 yrs old. Since early spring the safety switch on the Honeywell box that sits on top of the motor has been tripping. When I push the rest button the burner fires up right way. It can take anywhere from 12 hrs to weeks before it will trip again. In the spring when the burner was running often it tripped almost daily. Now it trips every 1-2 weeks. I have had a serviceman from my oil company out here on 2 occassions. I have replaced the motor, the honeywell switch, the electronic eye sensor and the proven switch on the venting system, but I still have the same problem. I am getting tired of replacing parts. The only thing I want to replace now is my oil company. Any suggestions as to what might be the cause? I am desperate to fix this problem. HELP PLEASE!