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The Human Diagnostic
Looking for honest stories about people, not product reviews? You're in the right place.
The Human Diagnostic isn't a how-to HVAC podcast. It's what a 45-year Master Technician notices about people after 90,000 service calls across gas plants, oil rigs, hospital preservation systems, high-rises, feedlots, walk-in freezers, and residential homes all over Central Oklahoma.
Hosted by Dave Hartzell, each episode tells a real story from a real service call. Sometimes he's driving to the job and predicting what he's about to walk into. Sometimes he just left and he's still working through what he saw. Either way, the story turns out to be about more than HVAC.
Topics you'll hear across the season:
✅ The customer nobody wanted to take, and what changed when someone finally did
✅ Why the person researching their broken AC at midnight isn't being difficult, they're scared
✅ What 45 years of walk-ins, weddings, funerals, and broken water heaters teaches you about anxiety
✅ The tech who can fix anything but can't explain it, and why the customer doesn't trust him
✅ The review you can't place, the moment you never forget, the call that changed how you work
✅ What gets lost when we treat people like tickets, and what gets found when we don't
Whether you fix things for a living, manage people who do, or just like good stories from someone who has been everywhere and met everybody, The Human Diagnostic gives you the part of the job that never shows up in an invoice.
📍 Proudly based in Kingfisher and serving Edmond, Guthrie, Yukon, Mustang, Piedmont, Logan County, Canadian County, Blaine County, Major County, Garfield County, and the greater Oklahoma City metro area. Hartzell's Heat & Air blends old-school integrity with cutting-edge technology, from digital diagnostics to smart-home HVAC integrations.
Connect with Hartzell's Heat & Air:
📲 Facebook: facebook.com/hartzellsheatair
🐦 X (Twitter): x.com/HartzellsHVAC
▶️ YouTube: youtube.com/@hartzellsheatair6003
💼 LinkedIn: linkedin.com/in/dave-hartzell-7a687515
📧 Contact Us: office@hartzellsheatair.com
Every call is a story. Every story is a person.
🔔 Subscribe to The Human Diagnostic and ride along.
📞 Need HVAC help in Central Oklahoma? Call (405) 375-4822
🌐 hartzellsheatair.com
Episodes
157 episodes
The Heat Pump She Suddenly Saw on Every Street
A customer in Hennessey told me, two weeks after I installed a new heat pump in her house, that she could not believe how many heat pumps were going in around town. She said she saw them everywhere. She named six driveways within a mile of her ...
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The Old Furnace Repair That Proved Nothing
A man in Calumet pointed at the furnace in his basement and told me they do not make them like they used to. It was forty-one years old and still running. He was certain that furnace was proof the old way was the better way, and that modern fur...
She Trusted My HVAC Truck Before I Fixed A Thing
A woman hired me once for a reason that had nothing to do with whether I was any good. She told me so herself, right there on the porch, before I had even opened my bag. I have seen your truck go by for years, she said. That is why I called you...
The Thermostat Problem That Was Really a Cold Chair
A woman in Okarche told me on the phone that her whole house was cold. She wanted me out the same day. I asked her where in the house she had measured. She had not measured anywhere. She just knew. I drove out. I put my hand on the suppl...
The Uniform of Calm I Put On for a Furnace Repair
A customer once told me I was the calmest man she had ever met. I thanked her. I did not tell her the truth, which was that I had been up since four that morning with a sick dog and a bad night, and the calm she was admiring was something I had...
The Air Conditioner Repair Where She Fed Me Lunch
Her air conditioner had been dead for two days in an Oklahoma August, and the first thing she did when I walked in was hand me lunch. Not water. Not a chair. A sandwich, made before I had my tools out of the truck. The house was hot enou...
The Broken Compressor She Swore She Predicted
A woman in Dover told me, right after I condemned her compressor, that she had known all along it was going to go out this summer. She said she had felt it. She said the unit had been telling her since spring. I asked her, gently, what t...
The Furnace Repair She Remembered Wrong On Purpose
A woman called me a year after a job to thank me for a furnace repair I barely remembered. It had been a long one. Her furnace quit on the coldest week of the winter, and I was at her house most of the day, pulling the blower, driving back to t...
The $2 Fuse She Tried to Pay Me For
A woman in Kingfisher tried to pay me for a fuse I had replaced on her fan motor. It was a two-dollar fuse. I had been at the house fifteen minutes, and I told her there was no charge. She did not believe me. She tried to hand me a twent...
The $2,000 He Buried in a Dying Furnace
A man met me in his garage with a manila folder full of receipts, and he laid them out on the workbench like he was building a case. A capacitor last spring. A blower motor the summer before. A control board somebody talked him into. He added i...
The Homeowner Who Spent Two Days Fixing His Own AC
I got a call last August from a house on the north edge of Okarche. The man had been working on his own central air for two days. He told me on the phone he was almost done. He just needed me to come verify a couple of things and maybe top off ...
The $15,000 Neighborhood Social Contagion
I worked a neighborhood out in Edmond for most of the summer of 2024. It was a development built around 2008, sixty houses, mostly two-story, mostly young families. I had two regular customers on the block when the summer started. I left the su...
The AC Rattle She Stopped Hearing: A Kingfisher Summer Repair
There was a blower motor in a house north of Okarche that had been telling on itself for the better part of two years, and the woman who lived there could not hear it. I could hear it from the driveway. I want to talk about that t...
The AC Repair We Both Swore Would Be Quick
I want to talk about the lie everybody tells themselves, including me, and tells it again the very next day. It was June, a Tuesday, north side of Kingfisher. A man called about his upstairs not cooling. He met me in the driveway already...
The Repair He Fumbled That Won Her Trust
I want to talk about the time a customer trusted me more because I screwed up in front of her. It was a March morning out past Okarche. Gravel drive, a propane tank along the fence line, the grass still that flat brown it gets before it ...
Why an Old Furnace Repair Takes Her Back to Seventeen
There's a kind of call I've come to recognize before I even get the unit open. It's an old house with one person in it, and that person has been waiting for somebody to talk to. You learn the signs at the door. The screen door has a part...
The Last Five Minutes of a Repair Are All She Remembered
I want to talk about how a person decides whether I did a good job, because it almost never matches what actually happened in the house. There was a furnace call back in January, deep cold, the kind of morning where the ground crunches a...
Why a Fixed Furnace Still Sounds Broken to You
She called me back four times in one evening, and the system was already working when she made the second call. It was a furnace that wouldn't cycle right. October, the first real cold snap, the kind that comes in overnight and makes eve...
Why Your Neighbor's AC Repair Makes You Miserable
I was at a customer's house in late spring. She was a woman in her early sixties, retired teacher, lived alone in a house she had raised her kids in. I had been to this house probably six times over the years on small things. New capacitor. Coi...
Why Missing an AC Deal Haunts You More Than the Repair
I got a call on a Tuesday in early August. Customer in a newer build out in Piedmont, second house from the corner on a cul-de-sac. He had not had any issue with his HVAC. Nothing was broken. The system was a builder-grade Goodman, ten years ol...
Why Her Neighbor's AC Repair Stung More Than Her Own
There is a customer of mine who runs a small construction company in central Oklahoma. He is in his early fifties. Started his business at twenty-six with one truck and a partner who quit on him in 2002. Built the company through the housing cr...
How Fear of the Bill Wrecks a Simple AC Repair
I had a customer about two years ago who could not let me find anything wrong with his house. Not because the house was perfect. The house was middle-aged, normal, had its share of issues. He had called me out for what he thought was a r...
Why Good Intentions Never Insulate the Attic
I have a customer who has been telling me for four years that he is going to insulate his attic. The materials are on his garage floor. Two pallets of R-49 batt, a roll of vapor barrier, a box of staples, safety glasses still in the plastic. Bo...
The Furnace Repair That Explained My Whole Generation
I have a category of customer in their forties who I find easier to work with than almost any other group. Mostly born between 1977 and 1983. A six-year window. Not Gen X, exactly. Not millennial, exactly. There is a name that got popular about...
Why Your Dog Knows Your AC Is Broken Before You Do
There is an old man in Hennessey who lives with a yellow lab named Gus. His wife passed in 2020. Same house since 1979. When I went out there for a no-heat call, the dog sat at his feet the whole time, and the man talked to me and talked to Gus...