Oil Furnace Transformer

Ignition transformers can be a fickle part.  The older ignition transformer would overheat and some of the insulation on the windings would get compromised. When the transformer cooled down it operated properly, when it was warm from use or being close to the flame inspection opening, it would not spark. Of course you didn’t know about it because by the time you discovered there was no heat, everything cooled off and resetting the primary control would light the burner just fine.     The electronic Ignition was supposed to solve that problem because it was thought that electronic ignition either worked or it didn't work.  Later on it was discovered that electronic ignitions had a different intermittent failure, so you have a similar difficult to find issue.  

Replacing the ignition transformer may solve the problem.  But it may not.   But that is the less expensive repair to start with.   I have enjoyed the benefits of the Carlin 70200 Primary control with many diagnostic features.  The history feature lets me know that for example 78 cycles ago there was no ignition. That tells me that the burner cycled 78 times since the customer pressed the reset button.  I can also see that 109 cycles before that and 216 cycles before that there was a similar failure.  There are other events like low amperage to the oil valve coil were recorded.  That leads me to believe the solenoid coil on the oil valve may be defective.  Replacing the ignition will not solve that problem.

I had a policy that the second time I visited a customer with a difficult problem to find, they would get a Carlin 70200 primary control. Sometimes that would fix the problem. After that control was installed, I could return when the intermittent problem happened again and read the diagnostic history and find that a different part was needed.  I could then replace that part and offer to remove the Carlin Control and refund the cost of the control. Most of the customers chose to keep the control because of the additional features.  I do remember refunding the cost of the control only 2 times.

So try the ignitor or the Carlin control.

Please confirm that you have OIL heat.

Does the motor run for about 30 seconds or so before it stops?

Do you need to push the reset button to get it to start again?

Now………this is very important:

How many times did you press the reset button? Be honest as a dishonest answer can kill you.

OK……….when you pressed it……………the furnace fired up properly? From your previous comments, it appears that the furnace would not fire and only the motor ran for 30 seconds or so. Then you pressed it again and the same thing happened……………no fire…………..then again……………then again…………….???

The details are critical to a proper solution.