TESTING AN IGNITION TRANSFORMER ON AN AFII OIL BURNER

PhilDavid

I met an AFII burner unexpectedly yesterday... there are few in my service area. Once I got my hands on one in a Beckett training class 3 years ago, not a big deal. But how the heck do you test the ignition transformer? It has two wires that stab onto the back end of the electrodes instead of probes that rest onto them. At least you can drag an insulated screwdriver across the probes of the AFG type to check the arc. Any suggestions?

the_donut

Damaged insulation somewhere shorting when wet would be my WAG.

lchmb

you can use the ohm test. Not perfect but usually leads me in the right direction..

newagedawn

turn on the burner and look for the light shining out the back of the blue sight glass, if its glowing its working, look somewhere else for your problem

newagedawn

if you have spark and the motor is running you have air, then all you need is fuel, humm, could be a fuel isssue

PhilDavid

lchmb said:

you can use the ohm test. Not perfect but usually leads me in the right direction..</

Am I checking for a specific resistance range or any resistance or OL

PhilDavid

The issue is intermittent ignition. Burner motor starts, ingitor gets 120v from primary, pump solenoid opens after 15sec (normal), fuel sprays into chamber but doesn’t ignite every time. The electrodes are new with no cracks good tips and set perfectly with Beckett T gauge. Im sure the connecting wires from the ignitor are not shorting. All indications are the ignition transformer but I’m not a change parts until it’s fixed kind of tech. I like to be certain as possible before I condemn a part. In a nutshell I want a solid way to check the AFII ignition transformer.

STEVEusaPA

What is the brand name, make/model of the transformer?
What is the make/model/ohms reading on the delay valve?
If it's an electronic ignitor, they make a test tool for that (don't know if it works-never bought one).
You can also ohm out the ignitor, and test it, depending on the brand, a few different ways.

EBEBRATT-Ed

if your spraying oil and the electrodes are set properly and not cracked etc you only have two possibilities why it won't light. Too much air or a bad transformer. You can check one of these

SuperTech

Ohm it. If you have a good transformer you can compare the ohm readings and you are done.
It kinda seems like you already confirmed that the transformer is bad by elimination.

lchmb

each post to ground... then take a post to post reading. The two post to ground readings should add up to the post to post. If off by 10% toss it.. also watch around the lead at the ignitor when it's working. I've seen the wire crack and go to ground causing a issue..

Leonard

Borrowed a hi-voltage meter for testing furnace ignition transformers once. Was so heavy and unlike any other I've used in electronics industry that I opened it up to see what so heavy. It was just another ignition transformer wired backwards to take the hi-voltage and make 120VAC again. Guess the nice thing was it drew current and loaded the 1-st tranformer's output, so might detect broken secondary winding.

It had a voltmeter on the 120 output. Meter scale was labeled in KV but I think meter was just a standard 120V meter with relabeled hi-voltage scale. Been a long time but I think I did check it with a 120V volt multimeter and it was 120 V.
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Most industrial voltage meters draw very very little current,so they can't load the circuit to find high resistance. As a kid had one say a car wire had 12V , but it wouldn't light the dome light, found heavily corroded green connector under the wet carpet. Used a test light from then on, it could load the circuit to find bad connections.
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I needed a ~ 5kv voltmeter once for checking a kitchen MW, didn't have it so I made one. Had a .01 amp AC meter hanging around. Looked at ohms law V=IR found I just had to add 500,000 ohms of resistance in series with meter. I was cheap so I salvaged the resistors from scrap old picture tube TV circuit boards. Think I ended up using ~ 8 resistors of the old ~ 1/2 inch long type, which was good so voltage across each wouldn't be too high and arc over. With higher votlage would want more resistors.

I only used it once , so I just "air" insulated it , (means just let bare wires hang in air ,edges supported by clean plastic. Laid it on plastic, used it then unplugged power before touching it again. ) Good to put meter in it's own case if regularly using it, regular meter likely won't be insulated to 15 or 30kv .

PhilDavid

lchmb said:

each post to ground... then take a post to post reading. The two post to ground readings should add up to the post to post. If off by 10% toss it.. also watch around the lead at the ignitor when it's working. I've seen the wire crack and go to ground causing a issue..

That’s exactly what I’m looking for thank you

HVACNUT

Dumb question, but the new electrodes are for an AF2?
HLX or F head?
The AF2 is VERY temperamental with air and electrode settings.
@newagedawn Is 100% right. Unwarranted disagree tagged. You can easily see spark by looking through the site on the back of the burner. It's not there for decoration.
The new igniter comes with the leads attached, and female spade connectors, so you can ditch the white leads and posts. Spade connectors should have been supplied with the new electrodes you purchaced.

Jamie Hall

Did you come up with anything? If not, I wonder -- this is a pretty wild idea -- if you could use an electric fence tester? The ones we have around the place are relatively inexpensive, and have five lights to indicate output voltage for the electric fence. They go up to 5 KV. Connect the lead to one terminal ore electrode and the sensor tip to the other (not your fingers, thank you!).

Might work... Tractor Supply has them. Might not work, too. Never tried it.

newagedawn

if its a selenoid pump could be that also, had one last week that actually stayed on after the burn cycle and melted the airscoop and the coupling into a plasitic ball, not a perty one,lol