blue and red swoop graphic

What Are The Symptoms Of Bad HVAC Transformer

By Aztil –

 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. 


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.

Request Service

What Our Clients Think Of Us

Aztil Air Conditioning
Based on 968 reviews
review us on
Dana was very pleasant and easy to work with. Nice that he was the same tech who came out last time so he was aware of me and my situation.😉
Dana is way beyond fabulous. He is knowledgeable, kind and extremely competent I am so thrilled with Aztil’s service
Wow!!! Ricardo did an awesome job cleaning my AC vents and dryer vent line. He was extremely clean and thorough. Be sure to ask for him as your technician. He really deserves acknowledgement for his hard work. Very happy!
Ricardo was very efficient and friendly good employee.
Great service Dana
Dana was here and did a great job
Dana Dussault is awesome.After 4 hellish days without A/C, he came to our rescue. My family and I thank you for your swiftness and professionalism.God bless you
Ricardo was very efficient and showed me exactly what he was doing. Very satisfied with the service!
Ricardo Campos was excellent when he came to my apartment today! He took his time and was very thorough. He went above and beyond any service man I’ve had!Next time I will request him personally!! Thank you, Ricardo!!
Dana was excellent , we seen him before, always happy with his work .
Easy. Expert and helpful. Dana. Good guy .💪.Ita 2024 and this time Ricardo came to do my service. He took pix of every service he performed. He was efficient and braved the heavy storms to get the job done. Really good guy
Response from the owner: Hi Valerie Pinhas,Thank you for your feedback! We're glad to hear that your experience with Dana was easy, expert, and helpful. We strive to provide top-notch service and it sounds like Dana did just that. We appreciate your kind words and we look forward to assisting you again in the future. 💪
Thank you for sending Ricardo to service The Rosado AC unit at 230 Andover I. I recommend Ricardo because he did a thorough job; keeping me informed during the time of his investigation and was polite and professional from start to finish.
Dana & Alex did a fast & clean job of replacing my drain line for my air conditioning.
Dana and Alex arrived for a service call today to solve an ongoing duct issue. They successfully removed a booster fan in the master bedroom duct! Dana and Alex are true professionals. Today they settled an ongoing issue I’ve had for over 2 months. I hope to see them again during any maintenance. Thank you!
We recently received AC maintenance from Ricardo Campos. He was very professional and cordial. He was prompt and got to work as soon as he got here. He explained what he was doing as he went along. He did an excellent job. We are very happy with Aztil we highly recommend it!
Ricardo came and did my yearly tune-up on my ac, I was very pleased and highly recommend ;
Dana found out the problem and took care of it quickly!
I highly recommend Ricardo at Aztil Air Conditioning. He is very professional and knowledgeable. He takes the time to explain why things need to be done and will inform you of alternatives and consequences if applicable. He is customer oriented and represent his company extremely well.
Dana was amazing. He cleaned and added a UV light to my a/c system. He is extremely polite and professional. I hope Aztil realizes what a great technician he is and an asset to the company. If I ever need help again, I want Dana to come.
I have been under contract with this AC company since 2013. They have kept me going since. Just got my usual 6 month tune-up, and my technician, Ricardo was excellent and very helpful, and answered all my questions. Highly recommend.
Response from the owner: Hi Bret, We're glad to hear that the technicians were courteous of your belongings and that Patty was helpful in scheduling the service. We take pride in our customer service and we appreciate your feedback. Thank you for choosing us for your duct cleaning needs.
Dana did a great job and was very professional! He was quick to diagnosis what was wrong and corrected the issue.
Dana provided fast professional service and I highly recommend him and Aztil.
Dana did a phenomenal job. Showed up on time, took care of some repair work, and had the A/C back up and running in no time. He also made it a point to keep me informed throughout the whole process and answered any question I had. Friendly and professional service! Thank you!
Very fast and efficent.Friendly and respectful.The only negative thing I could say is that they're much more expensive than anyone else.
Response from the owner: Hi Dennis, thank you for taking the time to leave a positive review. We are so glad that you had a positive experience with us!
I was having issues with my AC and was given an appointment immediately. Technician Dana was very professional, answered my questions and fixed the problem quickly. Very thankful that Aztil is able to provide great service and knowledgeable technicians.
Dana was professional and efficient. Tough to find these days! Thank you, Dana for your hard work!
Dana was on time and very polite. He quickly determined the issue and knew just what to do. The problem was corrected quickly. He answered my questions and explained the shut off safety feature on my AC unit so I would understand the codes. I would gladly have him back as a service provider.
Another great experience with Aztil. Technician Paul was outstanding. He identified the problem with our AC unit and got us back to a functioning AC system. I highly recommend Aztil for AC service.Our service included installing a new coil. Yohan and Pedro were terrific. They both were efficient and professional.Aztil completed the service on our AC unit today by doing a duct sealing. Cody and Kenny were both outstanding! I will continue to use and recommend Aztil!
Dana was absolutely professional and did his job quickly and efficiently AI would recommend him highly Judy and Frank Pisani
Dana is a Service PRO - knowledgable in all issues HVAC! Hire him with confidence knowing he will be thorough and successful in your air conditioning repairs! Google needs more stars for Dana!
Dana came and fixed my ac in 5 mins on a Sunday. Thank you!
Dana was promo and efficient. Five stars !
Dana was pronto didn’t even have to wait!!!! Took care of business and cooling off🥰😎😊😉
Dana,Dana arrived on time and we received excellent service from him. Would like Dana any time I need any service.
Dana is the best. He took his time and found out what the impossible problem with my air conditioner was.he gets 15 stars from me
I came home from work at 6:30 pm and the house was steaming hot. I called Aztil and within 2 hours Dana arrived. He was polite, professional and was able to get the air conditioning working within one half hour. I was so appreciative. Thanks Dana!
Dana was here AC problem fixed good job and thank you
Dana was great very trustworthy and did a great job at the Palmisano residence . 5 star worker 👍💪
Dana from Aztil Air Conditioning was exceptional. He diagnosed my problem immediately and was able to fix it in about 30 minutes. I have a service contract with this company and they were able to send Dana on short notice. Just the type of service you need when it's 90° and your AC stops working. Thanks to all their staff
Dana, came to the premises on time.Professional and efficient.Thank you for your service today
What amazing service‼️Ricardo and Yusnier today what an amazing experience with our duct cleaning crew, professional, fast and efficient .Thank you much‼️
Ana and the team are amazing!
Dana was here and great!
I recently contacted Aztil Air Conditioning to have my air and dryer vents cleaned. Ricardo and Yusnier arrived on-time and ready to work! They brought in their equipment quickly and made sure to be careful with my doors and floor. They worked meticulously and orderly, making sure to cover the area where they were working and not spread the dust around. They wiped down all of my air vents and made sure they placed the air vents in a manner that provided us with the best airflow. By the time they were done, it felt like we had a brand new air conditioner and there wasn’t anything out of place or dust residue from the service.I will definitely be calling Aztil back for more services and will surely be requesting Ricardo and Yusnier —they are THE BEST!

Our Partners

  • Carrier logo
  • Honywell logo
  • Mitsubishi Elctric logo
  • York logo
  • American Standard logo
  • Amana logo
  • Trane logo
  • Rheem logo
  • Ruud logo
  • Daikin logo