HELP.

I have a Lennox OF23Q3 oil burner. It is tripping out the safety button on the primary control erratically during operation. Sometimes it runs 20 minutes before tripping and sometimes only a few minutes. When it does trip the blower just constantly runs until the power is cut.

I have changed filter, nozzle, cad cell, adjusted the electrodes. With no help. I have also jumped the cad cell terminals as described in the service manual. It did not trip off which is supposed to eliminate the primary control as a problem.

Any idea what I should be looking at to repair it? Perhaps the blower control board?

Could be a weak transformer, or a air leak in the line. Or even a bad pump, did you bleed some oil in a cup and look to see how much air there was, or any water?

Was the burner firing (flame present) at the time you observed the primary control lockout? Does the CAD cell have a clear line-of-sight toward the firing assembly? I doubt the blower control is contributing to the problem in any fashion.

Was the burner firing (flame present) at the time you observed the primary control lockout? Does the CAD cell have a clear line-of-sight toward the firing assembly? I doubt the blower control is contributing to the problem in any fashion.

The burner was firing and I believe the new cad cell is aimed right at the flame/electrodes

I wonder why it would fire for 20 minutes before tripping the safety button? The safety button trips based on flame failure correct?

The pump was bled and is air free...

The CAD cell is very similar to a photocell. Its resistance varies with the level of exposure to light. The primary control is seeking an acceptable resistance value to prove successful ignition & sustained firing.

Check for pinched/damaged CAD cell leads.

OK I'll check the leads, perhaps replace them.

The old cad cell was dirty so not to take a chance we just replaced it.

Even though the furnace is 8 yrs old it is used in our 3 season 'camp' and has probably seen only a year's worth of use.

Thanks for your help.

With fuel oil units, more problems arise as a result of sitting idle than from running. Think of it as a diesel that is parked for months...

Yes I have found that out ! I have an outside tank full of 50/50 fuel oil.

Usually use the LP gas logs for heat but the women use the camp and have trouble getting it lit.

The furnace comes on and runs tills blower comes on , runs about 10 min. when blower stops, furance stops and furance will not come on again until you hit the reset bottom. This is when the house is cold.