Less Guesswork. Better Diagnostics. Fewer Callbacks.
Hands-on HVACR training that works when the boots hit the ground, brought to your location.
Why HVAC Compressors Fail — And How to Prevent Repeat Failures
Replacing the compressor is only half the job. In this live 90-minute session, learn how to find what really caused the failure so it doesn’t happen again. Live on Zoom with Don Gillis.
Learn on your schedule.
Short, focused HVACR video lessons from Don Gillis. Watch from the truck, the shop or home. Each lesson includes a quick reference PDF, a quiz and a certificate of completion. Pay once, keep access. Try your first lesson free.
Compressor Diagnostics: Find the Root Cause
Get a taste of Gillis Coach training at no cost. Prove a compressor failed, then prove what killed it, before the new one goes in.
HVAC Fundamentals: The 4 Main Components
Compressor, condenser, TXV and evaporator: what each one does and how they work together.
Charging a Suspected Low R-454B System
How to confirm an A/C system is really low on charge, then trim charge R-454B to the data plate target without slugging the compressor.
Training a whole crew? Ask about team pricing →
Target Audience
Training for every level of the HVACR business
Pick the group that fits you.
HVAC Technicians
Field training that cuts callbacks and builds real diagnostic skill.
Train the Trainer
Tools and teaching methods for your in-house trainers and leads.
Counter People
Help counter staff understand what the part does, not just the SKU.
OEM Partners
Product training that leads to proper installs and fewer warranty claims.
Tech Support
Rooftop-ready troubleshooting from someone who has been there.
Don Gillis
Don Gillis grew up in a small Ohio town, and he still calls it home. He started out at a mom-and-pop Lennox dealership, earned his journeyman license under the International Mechanical Code, and worked his way up as a service manager, territory manager and national technical trainer, including roles with Copeland and Chemours. Don has a real passion for the trade and the techs who keep it running. He has a knack for breaking complex topics down so they’re simple to understand, and he hates callbacks as much as you do.
- Former Senior Technical Trainer, Copeland & Chemours
- HVACR Journeyman License (IMC)
- BPI Building Science Principles Certified
- NATE-Approved Course Provider
- Top 25 Most Influential HVAC Educators, 2024
- CEUs offered nationwide, where state-approved
Certified. Licensed. Trusted.
Official documentation of training completion and field-proven credentials.
Certificate of Completion
HVACR Journeyman License (IMC)
Topics we cover
Every class is built around your team. These are some of the areas we can include. Mix and match to fit your equipment, market and experience level. Many qualify for CEUs.
HVACR Basics
The fundamentals never change, and every good diagnosis is built on them.
This is one of the topic areas we build into your custom training.
What you will learn
How the refrigeration cycle really works, pressure-temperature relationships, superheat and subcooling, and how airflow ties into all of it.
Why it matters
Techs who skip the basics end up guessing. Techs who know them can figure out equipment they have never seen before.
Questions? Contact us for more information
System Diagnostics
Stop guessing. Read the whole system before you replace a part.
This is one of the topic areas we build into your custom training.
What you will learn
A step-by-step process for diagnosing, what your gauges and meters are actually telling you, and how to find the root cause instead of the symptom.
Why it matters
Every wrong part is a callback, a lost customer and money out of your pocket.
Questions? Contact us for more information
Compressor Analysis
Hands-on compressor teardowns. See what failed, and learn why.
This is one of the topic areas we build into your custom training.
What you will learn
How compressors, controls and valves work, how to prove a failure before you condemn, and how to read a torn-down compressor (valves, pistons, bearings, windings) to find what killed it.
Why it matters
The failed compressor tells the story. Replace it without reading that story and the new one dies the same way.
Questions? Contact us for more information
Airflow & Static Pressure
If the air is not right, nothing else will be.
This is one of the topic areas we build into your custom training.
What you will learn
How to measure static pressure and airflow with the right meters, how to find duct and filter restrictions, and how airflow affects charge, comfort and efficiency.
Why it matters
A lot of refrigerant problems are really airflow problems. Fix the air and you fix the system.
Questions? Contact us for more information
Modern Equipment & Refrigerants
The industry is changing fast. Your techs need to keep up.
This is one of the topic areas we build into your custom training.
What you will learn
Heat pumps, inverter equipment, A2L, R-290 and CO2 refrigerants, safe handling, and communicating controls.
Why it matters
New refrigerants bring new safety rules, and inverter systems do not troubleshoot like the old ones.
Questions? Contact us for more information
Team Development
Training built around your people: installers, techs, counter staff, sales teams and trainers.
This is one of the topic areas we build into your custom training.
What you will learn
Programs fitted to each role, from field skills to customer conversations to teaching others.
Why it matters
A trained team makes fewer mistakes, keeps customers longer and stays with you longer.
Questions? Contact us for more information
What the industry says
I met Don nearly five years ago at the HVAC School Training Symposium. Since then, I have relied on him several times for technical advice. His expertise and willingness to share have helped me refine the curriculum at NCI. Don has earned his reputation through years of fieldwork and his dedication to industry education. He communicates complex topics in a way that is relatable to his audience. I consider Don both a friend and mentor. He is one of the most effective and well- spoken presenters I’ve had the opportunity to work with. Whenever I have a question, I know Don will answer the phone when needed.
What makes Don Gillis’ instruction valuable is his sincere and candid presentation. Don has personally experienced his subject matter from the ground up and that’s what adds relevance. Don Gillis is a gifted educator and story-teller. His clients benefit because his content is effective and applicable
Don has been an invaluable asset to the University of Northwestern Ohio and a trusted colleague for many years. As a longstanding member of our HVAC/R Advisory Board, he has consistently provided valuable industry updates, training, and expertise that have greatly benefited the university, our students, and fellow board members. Don has always been willing to assist in locating important information, offer thoughtful guidance, and provide knowledgeable advice whenever needed.
I’ve known Don for over six years in the HVAC industry, and he consistently goes above and beyond to help others succeed. He’s trained thousands across our organization on major industry changes and has helped create content that’s reached hundreds of thousands. Don is extremely knowledgeable, honest, and someone I trust without hesitation.
I’ve had the pleasure of attending multiple classes led by Don Gillis, and each experience has reinforced just how exceptional he is as both an educator and an industry professional. His ability to break down complex technical concepts into clear, practical insights makes his sessions incredibly valuable for both new and experienced professionals.
I met Don at the very first HVACR Training Symposium in South Florida. I sat in his class, then talked with him for quite a while at his booth about compressor technology. I could tell right away that he was passionate about our trade. What I didn't know was that he had worked in the field, just like me. Once I learned that, it all made sense: that's why he could relate to my questions so well.
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Short, focused HVACR lessons with a downloadable PDF guide, quiz, and certificate of completion.
Choose Your LessonJoin a live webinar
Work through compressor failures with Don and get your questions answered live.
See the Next WebinarTrain your whole crew
Arrange a private online or on-site session around your team’s equipment, experience, and training needs.
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Team’s Performance
If you’re ready to reduce mistakes, improve confidence, and build a stronger HVACR team — let’s talk.
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Why Compressors Fail (And Why the New One Will Too, If You Miss the Cause)
After 35+ years in HVACR, here’s what I’ve learned: compressors almost never die of old age. Something killed it, and if you don’t find the cause, the new one is next.