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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. 

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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Previous review 3/2025
This company is the worst!! The previous AC that I used Was sold to them and I thought I could Trust them like the last company! I spent Over 12k for a unit in May 2024 along with a 5yr service contract!!! that the salesman said would be the best unit and solve all my hot spot issues. Well it hasn’t! And because my “best” unit is digital NO TECHNICIAN knows how to work the unit. They are constantly calling tech support and still no one knows. I’ve had 4 different technicians here and no one knows what the hell they are doing!! I have Had technicians out 7 times to my home bc the humidity stays at 65-68%. No one knows how to adjust it. I called For emergency service on a Friday night bc my unit stopped working. They told me they wouldn’t have anyone until Thursday!! Do not use this company. They never call you back. Management does not respond. So unprofessional! I have Been trying to contact someone for over a week and no one ever returns my calls!! DO NOT USE THIS COMPANY.
I've been using Aztil for over 10 years. Always prompt, polite, knowledgeable, and professional. Today (Memorial Day), my AC went out. Within 2 hours, Albert was at my house and fixed the issue quickly. I would recommend Aztil to anyone based on my own personal experience with them.
The 4-stars is because I wasn’t informed of a scheduling change. After a little confusion regarding the appointment time the technician, Michael King contacted me. He arrived at the updated time. Was very professional and kept me informed about the service. He completed the job, cleaned up afterwards and thanked me for being a customer.
My service call was simple just clean the pipes. I asked the agent what was covered before I accepted and they stated clearing the pipes and other checkup. Well it did not turn out to be TRUE. I was charged for labor , materials(!) and other nonsense. NOT a Happy camper no one likes surprises! They are out of my list.
It always seems that the air conditioner breaks down on a hot day.
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Aztil is definitely the company for our household.
Michael King did a superb maintenance job. Plus, he made an extra effort to locate and install a part several hours after his first visit. Well done, Michael.
Dana was tech

Came out and went through central system and outside unit. Replaced thermostat as wasn’t reading correctly which was throwing hvac off from normal operation temps
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My wife and I have been loyal customers of Azril for years, and when the time came to get a completely new A/C system, we naturally chose Aztil to install and service a new system at our home in Boca. Our entire system just stopped a few nights ago, and I called the company . It was already 6:30, PM and it was getting very hot . Coincidently, Sabrina and I were setting up a routine 6 month check up a few days before our A/C incident . She was so friendly and professional , and said if there was any thing else she could do for me , not to hesitate to call.. WELL...needless to say ,I called her the night of the break down, and explained that my wife had lung issues, and needed to tag the service call EMERGENCY !! Not only did she make it happen, even ,though it was 8:30 PM, but kept calling me to keep us posted, several times !! She also sent Antonio ,who was as pleasant and professional as she. Fantastic experience, and the system is back to normal... Thanks team !! Steve and Caryn Silver Boca Raton
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First time using this A/C company but will keep using Aztil. Alex was my technician and very professional and explained everything. Needed new compressor and he made it very clear as to why and actually showed me the reading and it being low. Not pushy and very detailed and a nice young man who I will keep asking for to do my maintenance..
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Antonio was so polite and thoughtful by wearing booth covers over his shoes. He assured me that everything was running smoothly as it should and my ac was in good condition.

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Cody was an excellent technician. Polite professional and described each aspect of the maintenance. Kept me updated on the progress of the timeline .
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Nico arrived promptly. Assessed the situation and fixed the problem. He answered our questions and was very helpful. Thank you to Aztil for the excellent service on a busy Saturday. They took into account that we have a family member with a health problem.
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Niko was very polite, very professional and seems to know his profession.
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Dana was excellent in repairing our air conditioner! He was efficient, very knowledgeable and professional. He is simply the best!
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Antonio was our service tech and he did a Fantastic job. He let us know when he was go8ng to arrive, very polite and very helpful in his explanation as to what was happening and needed to correct
So very pleased with the result of his visit and his recommendation for future visits
Bravo Antonio
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Niko Garza, the technician from Aztil was wonderful, very professional and thorough. He texted me when he was on his way to do my 6-month maintenance service and did a very thorough examination of my air conditioning unit. He explained everything he was doing and explained the test results. When he was finished, he emailed me a complete report with pictures. I would highly recommend Niko and Aztil for maintenance of your ac unit.
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