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:
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The customer nobody wanted to take, and what changed when someone finally did
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Why the person researching their broken AC at midnight isn't being difficult, they're scared
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What 45 years of walk-ins, weddings, funerals, and broken water heaters teaches you about anxiety
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The tech who can fix anything but can't explain it, and why the customer doesn't trust him
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The review you can't place, the moment you never forget, the call that changed how you work
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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.
π 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.
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Every call is a story. Every story is a person.
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The Human Diagnostic
The Air Conditioner Repair Where She Fed Me Lunch
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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 enough that I could feel it in my chest. Her kids were cranky. She was stressed in a way she was working hard to hide. And her whole response to all of that was to take care of me.
For a long time I just filed that under people being nice. It is more specific than that. In 2000, a psychologist named Shelley Taylor pointed out that the old fight-or-flight picture of stress was built mostly on men. A lot of people, and her research found it more strongly in women, do not fight and do not flee under threat. They tend and they befriend. They pull their kids close and they turn toward whoever is standing there.
I have watched techs get this exactly backwards. A guy gets handed a sandwich and waves it off because he is busy, or reads it as the customer trying to butter him up before the bill. When you push that away coldly, you are not just declining food. You are shoving away the one thing her nervous system is using to hold itself together.
So I take the sandwich. I say thank you and I mean it. I let her show me where the kids are. Then I do the thing she actually needs underneath all that hospitality, which is to be calm and competent and fast, and make the threat to her house go away.
Forty-seven years in this trade has shown me the same thing about the guys who last. The ones who do not burn out are usually the ones who tend and befriend too. They check on each other. They call the older hand when they are stuck instead of white-knuckling it alone. The lone-wolf toughness looks strong. It is the connected guys who go the distance.
She did not need me to admire her sandwich. She needed me to take it, and then fix her house. So that is what I did.
Core line: "She did not need me to admire her sandwich. She needed me to take it, and then fix her house."
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Welcome to this deep dive. I am uh I'm so glad you are here with us today because we are going to completely rethink how you, me, and pretty much everyone around us handles a crisis.
SPEAKER_00Yeah, it's one of those topics that really turns everything you thought you knew completely upside down.
SPEAKER_01Completely. And we are pulling from two really fascinating sources to do this. First, we have a detailed reflection from Dave Hartzall.
SPEAKER_00Right, the master HVAC technician.
SPEAKER_01Exactly. He has spent 47 years in the trade operating out of Kingfisher, Oklahoma, and we are pairing his real-world boots-on-the-ground observations with a landmark psychology paper published by researchers at UCLA back in the year 2000.
SPEAKER_00Which is such a great pairing, right? The practical experience and the hard science.
SPEAKER_01It really is. Our mission today is to uncover a hidden biological stress response that we see every single day, yet almost always misunderstand. Because, I mean, we've all been taught that under pressure, humans just default to fight or flight.
SPEAKER_00Oh, absolutely. It's totally baked into our cultural vocabulary at this point.
SPEAKER_01Exactly. But today, we are going to look past that catchphrase. Okay, let's unpack this by heading straight to Oklahoma in August.
SPEAKER_00Aaron Powell Which, you know, is the perfect setting to observe human stress, honestly. Because in Oklahoma, August is an environment where extreme heat is not just uncomfortable, it is an actual physical threat to mammalian survival.
SPEAKER_01Oh, absolutely. So Dave Hartzel describes this specific service call in his reflection. The air conditioning in this particular house has been dead for two days.
SPEAKER_00Two whole days in that heat. Wow.
SPEAKER_01Right. When Dave walks through the door, the house is so hot he can physically feel the heavy air pressing into his chest. I mean, the environment is completely miserable.
SPEAKER_00Yeah, you can almost feel it just hearing about it.
SPEAKER_01The kids are cranky and the mother is visibly stressed. She is trying very hard to hide it, but the tension is palpable. The house is, for all intents and purposes, failing to protect the people inside it.
SPEAKER_00Well, it is a genuine crisis. Yeah. The core function of a shelter is compromised, and the environment is rapidly becoming unsafe, especially for the children, because you know their bodies cannot regulate heat as efficiently as adults.
SPEAKER_01So Dave walks in. He is the professional there to save the day. And what does the mother do? Before Dave even has his tools out of his truck, before he has even really assessed the broken unit, she offers him lunch.
SPEAKER_00A fully made sandwich.
SPEAKER_01Not a glass of water, not a place to sit and cool down, a fully made sandwich, ready to go. And reading this, my mind immediately goes to this bizarre scenario. Picture this.
SPEAKER_00Okay, I'm with you.
SPEAKER_01It has just hit an iceberg, the alarms are blaring, water is rushing into the lower decks, panic is absolutely everywhere, you are sprinting toward the lifeboats, and suddenly another passenger steps directly into your path, looks you dead in the eye, and says, Excuse me, would you care for a lovely cup of chamomile tea?
SPEAKER_00Right. It seems completely absurd on the surface.
SPEAKER_01Why on earth are we seeing hospitality during a literal meltdown? If your house is dangerously sweltering, why are you making a sandwich for the repairman?
SPEAKER_00Well, yeah, the the natural assumption, and the one most of us would make when faced with that scenario, is that this is just a homeowner attempting to be polite.
SPEAKER_01Or maybe on a slightly more cynical level, trying to butter the technician up.
SPEAKER_00Exactly. A quiet plea of like here is some ham and cheese, please do not bankrupt me with this repair bill.
SPEAKER_01Yeah, a bribe.
SPEAKER_00Right. But Dave realized over his decades in the trade, and the psychological research firmly backs this up, that we are looking at something entirely different. This is a profound biological stress response.
SPEAKER_01Wait, really? A biological response?
SPEAKER_00Yes. Her nervous system has seized the wheel, and it is driving her behavior in that moment just as powerfully as if she were physically running away from a predator.
SPEAKER_01But making a sandwich doesn't look like running from a predator.
SPEAKER_00No, it doesn't.
SPEAKER_01It certainly doesn't look like fighting one either. Which means to really understand why a sandwich is a biological stress response, we have to look at how science actually got stress wrong for a very long time.
SPEAKER_00An incredibly long time.
SPEAKER_01For most of the 20th century, the human stress response was entirely defined by fight or flight. Adrenaline pumps, heart rate spikes, pupils dilate, you punch the danger or you sprint away from it.
SPEAKER_00And that model goes all the way back to a researcher named Walter Cannon in the 1920s.
SPEAKER_01Okay.
SPEAKER_00Cannon's work was undeniably groundbreaking because he perfectly mapped out the sympathetic nervous system's reaction to a threat. He documented how the brain perceives danger, signals the adrenal glands, and just floods the bloodstream with adrenaline and noradrenaline.
SPEAKER_01Right.
SPEAKER_00He showed how blood is rapidly shunted away from the digestive tract and pushed toward the major muscle groups for immediate physical action. It was a biologically flawless map of a specific physiological cascade.
SPEAKER_01Wait, if Canon mapped the adrenaline cascade out so perfectly in the 1920s, how did this remain the only accepted model for 80 years? What exactly were they missing?
SPEAKER_00Well, they were missing half of the human population.
SPEAKER_01Oh wow.
SPEAKER_00Yeah, almost exclusively, early stress research, including those foundational studies that built the fight or flight model, was conducted on men.
SPEAKER_01That is wild to think about. They essentially look at how male nervous systems responded to threats, charted the adrenaline, and just confidently wrote down all right, this is how all humans react to every crisis.
SPEAKER_00That was the unquestioned scientific baseline. It wasn't until the year 2000 that the scientific community received a massive correction.
SPEAKER_01Which is the UCLA paper.
SPEAKER_00Right. Shelly Taylor and her colleagues at UCLA published a paper in the journal Psychological Review, pointing out this massive blind spot. When Taylor's team specifically structured studies to observe how women respond to stress, they discovered a neurological pattern that did not fit Walter Cannon's fight or flight model at all. Under threat, many people don't experience a primary urge to throw punches or run. Instead, they do something Taylor termed tend and befriend.
SPEAKER_01Okay, let's unpack those two words. What is physically happening during tend and befriend?
SPEAKER_00So tending involves turning toward offspring or the vulnerable, protecting them and nurturing them to ensure their immediate safety.
SPEAKER_01And the befriending.
SPEAKER_00Befriending involves reaching out and actively seeking social connection, essentially building a network of support to help manage the threat. And Taylor's crucial argument was that this is not just a psychological preference or a learned social behavior. It is a distinct, hardwired biological stress response.
SPEAKER_01Driven by hormones, right.
SPEAKER_00Exactly. Instead of being driven primarily by an adrenaline dump, it relies heavily on a completely different hormonal cascade centered around oxytocin.
SPEAKER_01Okay, I need to pause you there because my alarm bells are ringing slightly.
SPEAKER_00I figured they might.
SPEAKER_01Are we essentially arguing that evolutionary biology dictates men are heartwired fighters and women are hardwired homemakers and bakers? Because that feels dangerously close to a 1950s sitcom stereotype disguised as science.
SPEAKER_00What's fascinating here is that we really have to separate modern social constructs from the brutal reality of evolutionary biology.
SPEAKER_01Okay, tell me more.
SPEAKER_00Consider the environment of early humans. If a female was in the later stages of pregnancy or carrying a vulnerable infant, the classic fight or flight response was often a death sentence.
SPEAKER_01Right, you can't outrun a predator or carrying a baby.
SPEAKER_00Exactly. She could not outrun a predator, and engaging in physical combat would likely kill both her and the child. So from a purely mathematical survival standpoint, a different strategy was required. Tending to the vulnerable and befriending others to form a protective collaborative group was a highly successful way to survive a threat you couldn't physically overpower.
SPEAKER_01So it's an ancient survival mechanism born out of physical necessity, not a gender role.
SPEAKER_00Precisely. And while the UCLA research showed the tandem befriend pattern more strongly in women, partly because estrogen enhances the effects of oxytocin, this response exists in everyone today.
SPEAKER_01In everyone.
SPEAKER_00Men can and do tend and befriend. Women can and do experience explosive fight or flight responses. Most of us have the neurological wiring for both capacities. It is about how the brain decides to manage the perceived threat in front of it.
SPEAKER_01So if we take this science, this oxyposin-driven tend and befriend model, and we drop it back into that sweltering house in Oklahoma, suddenly the sandwich makes total sense.
SPEAKER_00It really does. The mother's house is feeling, the temperature is climbing to dangerous levels, that is a biological threat, and her brain's amygdala, the fear center, is sounding the alarm. But she doesn't try to punch Dave. And she doesn't abandon her house and run down the street.
SPEAKER_01She tends. Dave notes in his reflection that she pulls her kids close and gets them settled in the one room of a house that is still somewhat cool.
SPEAKER_00Securing the vulnerable.
SPEAKER_01That is the tending. And then her nervous system prompts her to connect with the stranger who has just walked into the middle of her crisis.
SPEAKER_00Right, because she does not have the technical knowledge to fix the air conditioner herself.
SPEAKER_01She is helpless against the threat. Yeah. So her biology commands her to secure an ally. She manages the terror through caretaking, she makes him a sandwich.
SPEAKER_00That is the befriending. It is ocytocin doing exactly what it evolved to do hundreds of thousands of years ago, binding individuals together for mutual survival.
SPEAKER_01Here's where it gets really interesting to me because Dave Hartzell talks about the friction that happens next. What happens when a technician who is operating in pure efficiency mode collides with a homeowner who is in a deep tend and befriend state?
SPEAKER_00Oh, it leads to a scenario that Dave calls the wrong move. And we see it in nearly every professional service industry.
SPEAKER_01Think about the typical technician. They have a packed schedule. They have five more houses baking in the sun that they need to get to. Time is money. Right. They walk into the sweltering house and suddenly someone is shoving a plate of ham and cheese in their face. The technician usually brushes it off. They say, No thanks, I'm busy. Just show me the thermostat.
SPEAKER_00Yeah, they kept their head down, focus on the machine, and treat the hospitality like it is an annoying interruption to their workflow.
SPEAKER_01Exactly. But why is that a problem?
SPEAKER_00Well, from the technician's perspective, they're being highly professional. Their nervous system is likely running on mild fight or flight, adrenaline, and focus to conquer the broken machine quickly. But psychologically, what they are doing to that homeowner is incredibly damaging.
SPEAKER_01It's like two gears spinning in opposite directions. Her nervous system is trying to engage the clutch with connection, and his nervous system is grinding the gears with isolation. Why is that rejection so damaging to her?
SPEAKER_00Because when a technician coldly refuses that sandwich, they aren't just turning down a free lunch. They are actively rejecting the exact coping mechanism that the homeowner's nervous system is currently using to manage sheer terror. Wow. The homeowner's brain has deployed oxytocin to secure help. When the technician weighs that away, they are essentially telling a panicked person, Your one available survival move. Yeah, it doesn't work on me.
SPEAKER_01Which means by trying to be hyper-professional, by trying to be fast and efficient and get the AC fixed in record time, the technician is actually making the emotional crisis worse.
SPEAKER_00Exactly.
SPEAKER_01They cutting the survival lifeline she just threw out.
SPEAKER_00Her nervous system says, connect to survive. The technician says, I reject your connection. The biological result is that her amygdala goes into overdrive. Her anxiety skyrockets because she is left stranded in a state of high alarm without a regulatory mechanism.
SPEAKER_01Okay, so if hyperefficiency and the cold professional brush-off isn't the answer, how should we respond? Not just HGC Texts, but any of us. How do we react when someone is desperately trying to befriend us or caretake for us during a crisis?
SPEAKER_00This is where Dave Hartzall's nearly half-century of wisdom truly shines. He figured out the right move. And it is deceptively simple. You let yourself be tended to within reason. You take the sandwich, you take the plate, you sit for 30 seconds, you say a genuine warm thank you.
SPEAKER_01Right.
SPEAKER_00You let her show you where she put the kids, and you look her in the eye, and reassure her that they will be cool again soon. You accept the biological bid for connection.
SPEAKER_01Because that befriending is doing real physiological work for her. By accepting the sandwich, you are allowing her oxytocin to successfully downregulate her fear response. You are helping her brain hit the neurological brake pedal.
SPEAKER_00Exactly.
SPEAKER_01But the core insight here, the thing that I found so profound in Dave's writing, is understanding what is sitting underneath that caretaking behavior.
SPEAKER_00Utter helplessness.
SPEAKER_01Yes. She cannot fix the threat to her household. The technician holds all the power to make the heat go away. So receiving the care isn't just about having good manners. Receiving the care is part of the repair.
SPEAKER_00I love that phrasing. The mechanical repair happens at the air conditioning unit, but the human repair starts the very moment he accepts the sandwich.
SPEAKER_01Dave has this quote in his reflection that I think should be framed on a wall. He says, She did not need me to admire her sandwich. She needed me to take it and then fix her house.
SPEAKER_00Right. He isn't saying you should linger for an hour chatting over lunch while the house continues to bake.
SPEAKER_01No, you accept the connection, which lowers her anxiety, and then you immediately pivot to the other thing she desperately needs, which is your competence. You quietly, calmly, and efficiently remove the danger.
SPEAKER_00Which is something I think we can all apply to our own lives outside of home repairs.
SPEAKER_01Oh, for sure. I'm thinking about times when a colleague at work is completely overcommed by a massive project deadline. And instead of asking for an extension, they suddenly start trying to organize my desk.
SPEAKER_00Or a partner who gets a terrifying medical diagnosis and suddenly decides they need to deep clean the kitchen and cook a four-course dinner from scratch.
SPEAKER_01Yes. Our instinct is usually to say, stop, sit down, you're stressed, don't worry about my desk right now. We try to logically shut down the unhelpful behavior.
SPEAKER_00And if we look at the neurobiology we've been discussing, shutting them down is the absolute worst thing you can do.
SPEAKER_01Because it traps them.
SPEAKER_00Right. Yes. By rejecting their unhelpful help, you trap them in a state of high arousal and increase their feeling of helplessness. Accepting their gesture, letting them tend to you in that small, seemingly irrational way is the fastest way to de-escalate their nervous system.
SPEAKER_01So let them organize the desk for five minutes.
SPEAKER_00Say thank you. Then, once their biological alarm bells have quieted down, you can help them tackle the actual project deadline.
SPEAKER_01It changes everything about how you view the frantic energy of the people around you. But it turns out this psychology doesn't just apply to the panicked homeowner or the stressed colleague. Dave points out that it applies equally to the people doing the fixing, the technicians themselves.
SPEAKER_00Which requires us to look at the deeply ingrained culture of the blue-collar trades.
SPEAKER_01Right. If you think about the HVAC industry or construction or plumbing, it has traditionally built on a very strict reliance on the fight or flight concept of toughness. Oh yeah. It is a culture that historically praises pushing through pain, never showing weakness, and handling every problem completely alone.
SPEAKER_00The classic lone wolf mentality. You get stuck on a difficult, complex repair. It is 110 degrees up in a cramped attic, and you absolutely do not call for help. You white knuckle it, you fight the mechanical problem until you conquer it.
SPEAKER_01And Dave acknowledges that there is a place for that kind of solitary grit. Sometimes you do just have to put your head down and push through. But his observation after almost 50 years of watching young technicians enter the trade and leave it is that the lone wolf approach has a severe biological shelf life.
SPEAKER_00Because if you rely solely on fight or flight, your body is constantly steeped in stress hormones. You are constantly triggering the sympathetic nervous system.
SPEAKER_01Just living on adrenaline.
SPEAKER_00Right. Day after day of operating on adrenaline and elevated cortisol leads to a massive physiological toll. It causes systemic inflammation, adrenal fatigue, and ultimately huge rates of professional burnout.
SPEAKER_01Dave noted that the technicians who actually last, the ones who make a lifelong career out of the trade without breaking down physically or walking away out of frustration, they are the ones who also utilize tend and befriend.
SPEAKER_00They build a network, they tend to each other by checking in on the younger, less experienced guys, and they befriend, meaning they aren't afraid to pick up their phone and call the older veteran technician when they hit a wall on a repair.
SPEAKER_01They utilize social connection to manage the stress of the job.
SPEAKER_00This raises an important question about how we as a society define resilience. We have spent an entire century equating toughness strictly with solitary endurance.
SPEAKER_01Which is so limiting.
SPEAKER_00It is. True toughness, the kind that creates longevity and sustains success over decades, requires building a web of people you can lean on. Both responses, fighting the problem directly and befriending a network for support are valid, essential ways a human body handles being overwhelmed, and we need both.
SPEAKER_01When we finally recognize tend and befriend as a legitimate, powerful survival strategy, we stop fighting against the people who are just trying to help us, and we stop isolating ourselves when we are the ones who desperately need help.
SPEAKER_00Absolutely.
SPEAKER_01Which brings us back to you listening right now. The next time you find yourself in a chaotic situation, maybe a literal emergency, or just a metaphorical fire at work or at home, and someone starts frantically trying to take care of you while their own world is falling apart, don't wave them away.
SPEAKER_00Recognize what is actually happening beneath the surface. It is their biology desperately trying to keep them afloat.
SPEAKER_01Accept the sandwich, accept the connection, say a genuine thank you, and then quietly and calmly help fix the problem.
SPEAKER_00I want to leave you with one final thought to explore on your own, building on everything we've uncovered today. If tendon befriend is a hardwired biological response that strictly requires human connection to regulate our nervous systems during a crisis, what happens to us in our modern app-driven world?
SPEAKER_01Oh, that is a great question.
SPEAKER_00Right. Today, if your AC breaks or your car stalls on the highway, or you need groceries delivered in a panic, you could just click a button on your phone to summon a fix. You don't have to greet the person, you don't have to look them in the eye, and you certainly don't make them a sandwich. Everything is engineered to be frictionless and contactless.
SPEAKER_01So convenient, but maybe a little costly.
SPEAKER_00Exactly. If we are removing the messy, necessary human interaction from our emergencies, are we accidentally engineering the biological comfort of befriending completely out of our lives? And if so, where does all that unresolved anxiety go?
SPEAKER_01Man, that is a question that is gonna stick with me for a long time. The tea on the sinking ship might seem crazy until you realize it is the only thing keeping the host from going under. Thank you so much for joining us for this deep dive. We will catch you next time.