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What Are The Symptoms Of Bad HVAC Transformer

By Aztil –

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 The HVAC system is the heart of your household. It is a machinery which consists of many big and small parts. In machinery as complex as that occurrence of a fault is normal. What is important is that you deal with them promptly and efficiently. The local HVAC company is your best answer. However, being a little proactive, you too should know a little about the things that could go wrong with your HVAC unit. If you have at least some basic knowledge, nobody would be able to fleece you easily. In our bid to educate you about the issues you could face in relation to your HVAC, today we shall deal with the transformer . The transformer of the HVAC unit is also susceptible to developing faults. But how can you be sure of that? This post will help you understand a bit more about transformers and also tell you about bad transformer symptoms in HVAC.

What Is A Transformer?

A transformer is a device which can increase or decrease the voltage of an alternating current or AC. It is a passive device which transfers electrical energy from one circuit to another. This is achieved through electromagnetic induction.

Role Of HVAC Transformers

Transformers are used when the incoming electricity voltage needs to be either raised or lowered to meet the requirements of the other electrical components or parts. The work of a transformer is to change the voltage that travels from the circuit board to the HVAC unit. This progression allows the air conditioner and the fan to work in synergy while cycling on and off. The usage of Electricity can be amplified or diminished depending on how much power is needed.

Where Is The Transformer Located?

In an HVAC unit, the transformer is located inside the furnace. But in a few cases, which is less than 10%, it can be found inside the AC unit situated outside.

Bad Transformer Symptoms In HVAC 

There are a couple of things which are indicative of a bad HVAC transformer. These are –

1. Humming And Vibrating – The humming sound in transformers is normal. It is produced due to the expansion and contraction of the laminations or the iron core. However, if there is a drastic increase in this sound, accompanied by strong vibrations, it is indicative of a bad transformer in your HVAC unit. There could be other possible causes of the humming sound and the vibrations like incorrect installation or a faulty capacitor. So, it is best to let a technician come and check out where the real problem lays.

2. Tripped Circut Breaker – When the transformer of your HVAC unit goes bad, the circuit breaker will usually trip. It trips so that there is no surge of voltage. A voltage surge can fry various parts throughout the furnace and AC causing a major breakdown of the said equipment. 

3. HVAC Not Working – With a bad transformer, your HVAC unit will not work even when it has an adequate power supply. This is a protective mechanism to save the unit from severe damage.

There is no sure-shot way of confirming that the HVAC unit is malfunctioning due to a fault in the transformer. This can only be discovered through the elimination method. The HVAC technician will start with the most probable and simple causes which could prevent the unit from functioning. When nothing else works, they will tackle the bigger causes, one of which being a bad transformer. 

Checking The Transformer Is Bad

Your HVAC unit is not working, and you have worked your way through all possible causes. Nothing seems to solve the problem. It’s time to call in the reinforcements who can validate your findings and look for the real problem. The things you were attributing to a simple problem could actually be bad transformer symptoms in the HVAC unit. In order to confirm that the problem is indeed the transformer, you need to check it. For this, you need a multimeter, as well as the basic knowledge of using it. A faulty transformer gives an infinite or wide-open reading while a transformer without any fault reads between zero to 10 ohms which is indicative of a closed circuit. 

Causes Of A Bad Transformer

Bad transformer symptoms in HVAC unit may appear due to the following reasons –

1. Bad Contactor – More often than not, it is a bad contactor which leads to a blown transformer. A bad contactor puts the entire unit under a lot of stress. When the tension or strain becomes too much for the unit to handle it mostly results in a blown transformer.

2. Wiring Issues – Loose wires or cables inside the transformer can cause a short circuit due to which the transformer may fry.

3. Power Surge – An electrical failure in the form of a power surge can also cause transformer failure. 

Can I Replace The Transformer In My HVAC Unit?

If you are a trained technician who knows the ins and outs of a transformer, you can definitely do this job yourself. However, if you are not, you better think twice before taking on the job. Ask yourself whether it is worth paying a trained technician to do the job correctly? Or you are willing to foot the bill for a new HVAC unit if you make a hash of things? The answer will lead you in the right direction. 

Conclusion

Time and again, electrical equipment malfunction. The good thing is that a malfunction does not mean you need to buy a new one. Today, you can simply replace the faulty or the bad component and your machine will be as good as new. HVAC units are no different. You can replace the part that has fried or melted, and once that is done, it will start functioning as normally as before. A few things to keep in mind are – take good care of your HVAC unit through regular maintenance and try to refrain from carrying out any repairs yourself. 

If you are not careful, you may do more harm to the unit and maybe even get hurt or injured. There are people who are trained to care of such things, and they even have the necessary tools and replacement parts to complete the job quickly. Book an appointment with your local HVAC company if your unit is behaving abnormally. They are the most trusted people to take care of things immediately.

Frequently Asked Questions

If your transformer is bad, you will have a tripped circuit breaker. It tips to prevent a voltage surge which can fry various parts inside the HVAC system resulting in a major breakdown of the equipment.

Similarly, a transformer with clear burn marks or a bulged exterior is also a sign of a bad transformer.

You may face any of the following issues when the furnace transformer goes bad:

1. There is a loud humming sound coming from the unit with a dramatic increase in vibrations.

2. The circuit breaker trips frequently.

3. The unit stops working correctly even with an adequate power supply.

You can test an HVAC transformer using a multimeter. First, switch the multimeter to “Ohms.” Next, disconnect the electricity from the transformer. Now attach the multimeter and check the ohms reading for the primary and secondary windings. Ideally, the reading should be between 1 to 10 ohms. If it is higher, the HVAC transformer is bad.

There are several reasons that could lead to the HVAC transformer failure. Some common causes are corrosion, wear and tear, overloading, power surge, fluctuations, moisture, strong winds, rain, and lightning strikes.

Mostly, the transformer will burn when the load on it becomes too great. Sometimes sunlight on wires rots the insulation and shorts them. The other probable reasons are loose wiring, worn-out parts, and the accumulation of dust on the transformer.

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Michael was really great and he explained everything pretty well for me to understand
Update 8/16/2025

I’ve been a loyal customer of Aztil AC Company for several years, and I can confidently say that they have consistently demonstrated honesty, reliability, and exceptional service. My brand-new Rheem A/C unit, installed in October 2023, unfortunately required a new fan motor.

Aztil AC Company promptly sent Rafael to diagnose the issue. He efficiently completed the necessary paperwork to ensure that the part was covered by warranty. The cost of the service was $75, which included filing the paperwork and the repair.

On a Saturday at 1:00 AM, the AC unit suddenly stopped working. The next morning, at the earliest, Aztil AC Company sent Ramon to assist us. Ramon was an incredible technician! He quickly diagnosed the problem and helped us clean the AC drain line. As a result, we had cold air flowing immediately.

Ramon was not only professional but also incredibly efficient in his work.

I contacted Aztil Air Conditioning to request service for my air conditioning unit. I spoke to Ronda, who provided excellent service. She was very helpful, friendly, and had clear, professional, and transparent communication.
Response from the owner:Hi Sergey, thank you for your kind words! We're so glad to hear that Ronda did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Michael from Aztil came by today and fixed our AC problem. He was polite, professional, and did a great job. We are glad we have Aztils maintenance program.
I had again found that I had no ac in my house. Your tech Michael came out within 24 hours and not only fixed it, but also took the time to tell me how to stop it from happening again! He was fabulous! Even at installation, no one ever told me what I was supposed to be doing! You have a great asset in Michael!
Response from the owner:Hi Patricia, thank you for your kind words! We're so glad to hear that Tino did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Your service techs and general service has improved since the corporate take over. Raphael Curci was efficient and kept us u[p to date on the progress of the installation. The person I'd like to call out as exemplary was Nico who guided us through the process and went out of his way to help us through this time.
Ramon explained in detail what he was doing and how to prevent issues. Ramon is a credit to Aztil. This a/c company has wonderful systems in place to protect their customers homes. Highly recommend Ramon as technician and Aztil for your a/c maintenance and repairs.
I LOVE this company and Nico is hands down the number one technician on the team. The maintenance plan is worth every penny and I never have a problem getting anyone out when I need them.
Toni did a fantastic job! I believe he also did a very thorough job in all areas of our AC unit. He advised us of some areas of our unit that was building up mold and what needed to be done. The concern I had was why no other techs that come out every 6 months hadn’t brought this to our attention. Toni is very personable and he took the time to explain everything to us and I could tell that he is concerned about customer satisfaction. Appreciated all his efforts. Excellent Tech! We will request him to come back in 6 months again!
Michael performed well and was very friendly.
Cody was extremely professional and very courteous!! His knowledge and expertise takes him a 10 plus!! When I call Aztil I only want him to service my AC..
Thank you Aztil for sending Cody for my repair. He is an asset to your team!!
Donna
Response from the owner:Dear Donna Matos, Thank you for your kind words about Jonathan M. We are glad to hear that you had an excellent experience with him and we agree that he should be training our complete service department. We are sorry for any past poor service you have experienced and we appreciate your feedback. Sincerely, Donna P. Gliner
Paul was the very best. Knowledgeable and very professional!!!
Michael is a Great Tech whom I highly recommend.
Response from the owner:Dear Jack Derriss, thank you for your fantastic review of our team members Nicholas and Jonathan. We are thrilled to hear that they provided excellent service in repairing and replacing the breaker part for you. At AZTIL, we strive to meet all of our customers' A/C and heating needs, and it means a lot to us that you highly recommend our services. If you ever require any further assistance, please don't hesitate to reach out. We appreciate your support!
Tino did a very good job
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Michael came out addressed the service problem which I really was when he cleaned out the pan and he was quick
Michael our Technician today was excellent. The inside and outside units were thoroughly examined and test equipment was applied to both of the units to show a positive outcome. Thank you for sending us Michael; we would very much like it if you would send him again. I have confidence in his work and in your companies
excellent service.
Tech Juan Ortega was great to work with. He explained everything in detail and answered all my questions. I will definitely be calling Aztil Air for my upcoming HVAC needs.
Michael King was very pleasant to communicate with and answered my questions fully.
Awesome service. Dana arrived shortly after we placed our emergency call and within a short time our AC was back up and running. Highly recommend Aztil AC!
The service tech Dana did an excellent job doing the repair of the compressor and my ac is working great again!!!! Very friendly and courteous, Highly recommend!!!!
Response from the owner:Hi Chris, thank you for your kind words! We're so glad to hear that Ramon did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Niko done a super job. Did everything involved with the a/c. He is a very nice guy. Would love to have him back. :)
Aztil is a very reliable ac company TINO did a great job with my air conditioner he took the time to explain to me how to use my thermostat and answer all my questions thank you Aztil I will recommend you to my friends and family
Michael King was amazing!!!!!!
Called them and Niko Garza was at moms house with in 15 minutes didn't take long for him to get my A/C running Niko is a nice person
Skyler and Alex did a wonderful job very pleasant guys I was very comfortable with them thank you guys for the wonderful job
Aztil tech Jorge Rivera is to be commended for staying up in my very hot attic to install my new air handler. He did a great job. His patience as I connected my new smart thermostat and set up everything so I could control my thermostat from my phone.
Thank you for your quick response and good work.
Response from the owner:Hi Lynn, thank you for your kind words! We're so glad to hear that Jorge did an excellent job with your new Installation and that you were pleased with the outcome. Thank you for being a valued customer.
He was very good at what he does
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Cody was our technician. He promptly diagnosed the problem and fixed the problem in a timely manner. Very professional.
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Paul came to check the A/C compressor and handler. Took pictures and showed me. Both units were disgustng.. He gave me the amt of replacing. I Absolutely agreed. Then Neraldo and another Technician came and installed the AC units. Next
Jordan and Adrian came and cleaned all vents and ducts. All 5 of them were excellent and friendly. Also gave me the info on what was being done. 5 stars for each one of them. Highly recommend

I have had a Dual Inverter installed in my back room. Jorge did the install and was Terrific. He worked his butt off and in the heat. David his helper was on the go the whole time. This is my 2nd AC install with Aztil AC and I would Highly reccommend them. They are polite, efficient, and hard workers. Thank you So Much Jorge and David. If I could go over 5 I would give you 10 stars.
Response from the owner:Hi Barbara, thank you for your kind words! We're so glad to hear that Paul, Neraldo, Jordan and Adrian did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Great duct cleaning work performed today. Jordan and Hero were very profesional, productive and attentive. Extremely thorough work was performed.
Response from the owner:Hi Frank, thank you for your kind words! We're so glad to hear that Jordan did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
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