RearAdmiral
Platinum Member
Full tale as follows, TLDR at bottom.
I came home Sunday evening to find my heat was not kicking on. I did a few troubleshooting measures that night but figured we would be okay until morning if I couldn't fix it and had to call a service in, as I wasn't about to call someone at 10pm and pay $500. So we brought our portable oil radiator into the bedroom and used that for the night. The following morning I started my in depth troubleshooting.
We have an oil fired forced air setup. Last year we had a very similar issue in which the heat call would shut off after 45 seconds or so, which turned out to be the CAD cell which is the sensor that physically looks at the flame to make sure it is actually burning when it is supposed to be, and cuts the call off when there is an issue. So naturally that is one of the first things I checked. I pulled the sensor out, give it a little cleaning, and used my meter to test the resistance in light/dark. All appeared good from there. I reset the system and it did not start correctly again, and now I started to notice there actually wasn't even a flame now, unlike last year where it at least lit. I started to get a bit nervous at this point but I pulled up some youtube vids and would keep going until I felt unsafe.
I made sure I had fuel pressure at the pump and that there were no obvious clogs(I had done this previously so felt okay). Everything else from here was all new to me. I then disconnected the fuel line and removed my oil gun to view the nozzle and the electrodes, which was kinda fun to see that mechanism. I could also see my combustion chamber then which was again interesting. The nozzle appeared clean and the electrodes were in a good position, nothing was really dirty / sooty. I wasn't about to pull apart the nozzle either. There was some fuel on the nozzle / in the gun so I figured fuel was at least flowing. If the nozzle was a problem, I figured I could replace that easy enough but would leave that to a pro just in case, so I tabled that issue.
So it appeared that I wasn't getting a spark, which to my untrained knowledge was somewhat unlikely, but the other "easy" stuff was out of the way at this point. Next was to do the unofficial testing of the transformer. I picked up a good tip at this point which was to disconnect the power to the fuel pump so you don't pump too much fuel in the combustion chamber and create a dangerous situation. So I did that and prepped to "safely" arc the transformer with a screwdriver. I put on a rubber gardening glove, then another glove and used a rubber screwdriver too. Overkill I imagine as the videos all had guys do it barehanded but I was still worried. I squatted down and leaned back a bit so if I got electrocuted I would hopefully go backwards lol. I disconnected my CAD cell, reset the system and arced the transformer and nothing happened. I really did not think the transformer would be a problem, so I got another different screw driver in case mine was weird and non-conductive for some reason. Again no spark. So at this point I found it odd that the transformer went bad out of all the servicable / consumable components but there was no other explanation atm.
Off to the internet again to view replacement parts / prices. Online cost for a transformer was about $40-50, but I needed heat now. I found a localish hvac place that serviced consumers and called to verify they would replace my part. I got to the place, mentioned I had called about a transformer and set the old one on the counter. The guy asked me why I thought it was bad. I said I did the spark test. He asked what I got across the spring terminals, and I said "nothing." He seemed in agreement at this point and went off to get a replacement. His reaction to my troubleshooting did not fill me with confidence and I got the feeling he had been down this road before with no nothing consumers(like me). $70 bucks later I was on my way back regardless.
I crimped new connectors on the wires, installed the transformer and ran another test, to which I got a vigorous spark! I put everything back together and reset the system a final time, to which I got a flame and thus heat to my house, hurray! I was only 11 or so degrees below my set temp at this point but it was getting a little chilly.
I think my high limit switch was tripping though, as my t-stat was going on / off during the heating which may / may not be a problem as I am usually not heating up 11 degrees at a time. I'll have the pro take a look at my next service though in case I am not getting good enough airflow.
I learned quite a lot, did not do anything super dangerous that I could not undo and fixed the problem, and probably saved $400 too! Very satisfied.
TLDR:
Transformer went out on oil forced air furnance, managed to diagnose / replace myself.
I came home Sunday evening to find my heat was not kicking on. I did a few troubleshooting measures that night but figured we would be okay until morning if I couldn't fix it and had to call a service in, as I wasn't about to call someone at 10pm and pay $500. So we brought our portable oil radiator into the bedroom and used that for the night. The following morning I started my in depth troubleshooting.
We have an oil fired forced air setup. Last year we had a very similar issue in which the heat call would shut off after 45 seconds or so, which turned out to be the CAD cell which is the sensor that physically looks at the flame to make sure it is actually burning when it is supposed to be, and cuts the call off when there is an issue. So naturally that is one of the first things I checked. I pulled the sensor out, give it a little cleaning, and used my meter to test the resistance in light/dark. All appeared good from there. I reset the system and it did not start correctly again, and now I started to notice there actually wasn't even a flame now, unlike last year where it at least lit. I started to get a bit nervous at this point but I pulled up some youtube vids and would keep going until I felt unsafe.
I made sure I had fuel pressure at the pump and that there were no obvious clogs(I had done this previously so felt okay). Everything else from here was all new to me. I then disconnected the fuel line and removed my oil gun to view the nozzle and the electrodes, which was kinda fun to see that mechanism. I could also see my combustion chamber then which was again interesting. The nozzle appeared clean and the electrodes were in a good position, nothing was really dirty / sooty. I wasn't about to pull apart the nozzle either. There was some fuel on the nozzle / in the gun so I figured fuel was at least flowing. If the nozzle was a problem, I figured I could replace that easy enough but would leave that to a pro just in case, so I tabled that issue.
So it appeared that I wasn't getting a spark, which to my untrained knowledge was somewhat unlikely, but the other "easy" stuff was out of the way at this point. Next was to do the unofficial testing of the transformer. I picked up a good tip at this point which was to disconnect the power to the fuel pump so you don't pump too much fuel in the combustion chamber and create a dangerous situation. So I did that and prepped to "safely" arc the transformer with a screwdriver. I put on a rubber gardening glove, then another glove and used a rubber screwdriver too. Overkill I imagine as the videos all had guys do it barehanded but I was still worried. I squatted down and leaned back a bit so if I got electrocuted I would hopefully go backwards lol. I disconnected my CAD cell, reset the system and arced the transformer and nothing happened. I really did not think the transformer would be a problem, so I got another different screw driver in case mine was weird and non-conductive for some reason. Again no spark. So at this point I found it odd that the transformer went bad out of all the servicable / consumable components but there was no other explanation atm.
Off to the internet again to view replacement parts / prices. Online cost for a transformer was about $40-50, but I needed heat now. I found a localish hvac place that serviced consumers and called to verify they would replace my part. I got to the place, mentioned I had called about a transformer and set the old one on the counter. The guy asked me why I thought it was bad. I said I did the spark test. He asked what I got across the spring terminals, and I said "nothing." He seemed in agreement at this point and went off to get a replacement. His reaction to my troubleshooting did not fill me with confidence and I got the feeling he had been down this road before with no nothing consumers(like me). $70 bucks later I was on my way back regardless.
I crimped new connectors on the wires, installed the transformer and ran another test, to which I got a vigorous spark! I put everything back together and reset the system a final time, to which I got a flame and thus heat to my house, hurray! I was only 11 or so degrees below my set temp at this point but it was getting a little chilly.
I think my high limit switch was tripping though, as my t-stat was going on / off during the heating which may / may not be a problem as I am usually not heating up 11 degrees at a time. I'll have the pro take a look at my next service though in case I am not getting good enough airflow.
I learned quite a lot, did not do anything super dangerous that I could not undo and fixed the problem, and probably saved $400 too! Very satisfied.
TLDR:
Transformer went out on oil forced air furnance, managed to diagnose / replace myself.
