HVAC reviews in Anaheim, California

We had a new HVAC system installed in our home 22 years ago. From the beginning it never seemed to work right but were we assured there was no problem. In mid-December 2025 the heater quit working. We called Marathon as the HVAC contractor who installed the system was long out of business. Technician Eric Gonzales spent over an hour in the attic testing/observing operation of the heater. The thermostat was bad, but there was another problem. The upshot was the heater burners ran about seven minutes and then shut down when the over-temperature safety activated. However, the air circulation fan kept running and the burners later re-ignited once air movement rectified the over-temperature matter. Eric observed this on/off/on/off cycling several times and he identified the root cause of the problem – the air intake was undersized by 40%. Eric presented/explained three options, and after he answered questions we decided on a new heater system. I’ve delayed posting a review because I wanted to wait and see whether our new unit works better than the old unit. It definitely does. The installation went very well and there was immediate follow-up to ensure proper installation and operation. Too bad we didn’t call Marathon 20+ years ago.

Marathon installed a new Samsung unit in 2022. In 2025 the unit failed. All the coolant had leaked out and had an error code.
Tech didn't do basic pressure test to try to locate the leak. Another company I spoke to said an experienced tech would know to check the flare fitting first. It's a common cause of leaks. A homeowner doesn't know these things.
So, instead of a pressure test, a pricey $2,400 isolation test is booked.
Later I find out that other companies charge $1,500+.

After complaining about the upsell, the boss calls me and offers a comp pressure test and a discount on the isolation test. The pressure test that's the normal protocol located a faulty flare fitting. Marathon repair that. Then to refill the unit with coolant per lb was (again) more expensive than others.
Overall, didn't like dealing with the company and the poor advice from junior techs they send.
Bottom line, Marathon installed a new unit. It failed within 3 years. My general contractor who hired them doesn't use them any more. And he said he's never seen a new system fail so quickly.
There are plenty of other HVAC companies. Try Efficient HVAC in Azusa.

Joziah, from Marathon HVAC, came out to do a maintenance check on our heat pump last summer (2025). (We have a monthly paid plan which gives us two maintenance visits a year to keep our heat pump functioning well.)
He was awesome. From his easy manner and professionalism to his ability to be a friendly presence dealing my suspicious dog Buddy, I have nothing but praise for Joziah and the great job that he did. (By the time he left, he and Buddy were old friends.. 😄)

I don't know a lot about air conditioners or heat pumps but he let me know a little bit about how they work and he was very careful to make sure everything was cleaned off, functioning well and ready for us for the winter.
We will definitely be having him come back soon to check out our heat pump and help it be ready for the summer.
Thanks, Joziah!

Justin R did a great job. He called before arriving and followed every step to ensure the machine was working properly. He changed the filter and checked all the measurements. I would highly recommend him.

Leo showed outstanding professionalism and great communication skills. He was able to quickly pinpoint the root of the problem, which I truly appreciate.

Corinna at the front desk was also very responsible, patient, and helpful.

I also noticed that the company has very strong reviews on Yelp. Working with a company like this feels transparent and trustworthy, which gives great peace of

If you want someone to get the job done right the first time this is right company. Highly recommend Delta T.

Delta T did a great job. The team was prompt and professional. I highly recommend.

Delta T is the best HVAC company around. Nick is honest and knowledgeable. He came in significantly lower than the other bids I got and did a fantastic job. He installed a new a/c unit and relocated our furnace up to the attic so everything is much quieter and cooler at our house now!
I highly recommend this company and now many of my neighbors have used him as well!

Nick was absolutely amazing. His quote was fair and honest, and thousands less than some of the others we received. My neighbor recommended Nick, and I'm so happy that we went with Delta T. They finished our entire job in two days, including relocating the HVAC to the attic. We now have a quieter, more efficient system, thanks to Delta T.

Friendly

Fast service

McQuay distributor

Nice company

Great company

Good job fellas

Great service!!

customer service is on point.

Quickly get accurate quotes

Best HVAC supplier in town.

Poor communication skills.

POOR CUSTOMER SERVICE. NO COMMUNICATION, NO APOLOGIES WHEN WRONG, AND LACK PROFESSIONALISM.