How to troubleshoot the transformer

I discuss the low voltage transformer used in HVAC units. Voltage checks are shown to troubleshoot low voltage problems.
If you are a homeowner looking to repair your own appliance, understand that the voltages can be lethal, the fuels are highly flammable and high pressures are used. Know your limits.

[grayfurnaceman]

Take a look at "How to replace a transformer without blowing up the new one". And you are right, transformers seldom fail. Thanks for the comment.
GFM

[grayfurnaceman]

Generally, transformers fail from shorts in the system or overloads from things like contactor armatures sticking. The transformer itself is very dependable.
GFM

[EddieLeverich]

Usually a short in the system if you find a blown transformer and some shorts can be a pain to locate

[grayfurnaceman]

As transformers seldom fail, I would guess there is a problem with the board that is causing a short. If the board changes the low voltage power to DC, the diodes in the rectifier could have shorted. You can look for bad solder joints on the components if the board just does not work, but if it is shorted you would need knowledge of semicouductors. Hope this helps.
GFM

[louisviciedo]

I just moved into a new home and want to instal an ecobee. I went to the transformer and only have 1 segmenet of 24v through the RED secondary, the GREEN secondary is grounded and doesnt have constant 24v. The GREEN wire is connected to my BLUE C wire. the result is that Im not getting constant power to my thermostat C wire. Is this a wiring problem?

[grayfurnaceman]

Opps, I did not follow up on that one. Thanks for the reminder. I will be doing that one probably tonight. It will be also located on the "control transformers" playlist.
GFM

[jheromeberon]

I have a 24v transformer but the output was only 20v, , it was the reason why transformer tripping off

[kalimanx]

Thank you for this lesson. Good job on explaining the troubleshooting process.

[grayfurnaceman]

If you are testing with the ohmmeter, the finger will not upset the readings.
GFM

[andygeibe]

Just started school for hvac. Awesome to have your videos to help me understand what I learned in class

[StagArmslower]

I have humidifier's transformer burning out in few months of running. The water valve
solenoid draws 1.2 amps at 24 VA it's 29 watts. Transformer is 40 watts. The voltage to primary winding is connected (as installed by technician) to blower connector; one neutral and L1
(120 volts)so valves opens when blower operates. Any suggestions why this happens, maybe spike from blower's capacitor, any sugestions

[sgtbigtoe]

I recently replaced the contactor on my goodman heat pump/ A/C out side unit, the contacts were melted together, I replaced the contactor and the heat pump worked again while the weather has warmed the A/C wasn't coming on after checking many possibilities I gave the transformer a smack with a screw driver and it's started working again, hopefully for good, not sure if that was the cause or I just wiggled the right wire some where

[toxicsneeze]

What if I DO have continuity on both the primary and secondary side but when I hook the thing up I still get no voltage on the secondary side? Clean 121v on the primary side... I've gone through ur whole series and I'm still at a loss. I'm on transformer #3... I have no continuity on on relay side (with transformer unhooked) in the open position (like it should be) and now I have 3 seemingly dead transformers so I can't test for amperage on my equipment side either.... I'm mostly just ranting... This is frustrating. Thanks for the help u did provide....

[Dear]

My mother in laws house had a power surge from broken exterior power line …..it fried a few household appliances …. Lennox elite Furnace has no power do you think it could be the transformer?? Circuit breaker is fine and has 110 at furnace

[rdoonanco]

what should the primary side have for resistance if it is working? I've tested my transformer and it has 2ohms resistance on the secondary side and 25.5ohms on the primary. Thanks

[ShaneArmada]

I bet its one of those
fkin hampton bay transformer

[bobbyatman]

Putting wires "here" testing "there" ifc...

[rymn]

HVAC student here about to graduate. i have been obsessed with your videos for hours now. great videos

[tommonti]

I have a  York 025-28671-000 HVAC Transformer. Should the transformer be hot to the touch of the finger when I have all breakers turned on but the ac unit turned off?

[raycarr]

Can't find anything on testing for mA AC. Specifically, a transformer with an output of 15v AC/500mA AC rating.