5 Costly Mistakes I Made with Commercial HVAC Units (And the Checklist That Saved Me)

Who This Checklist Is For

If you're a facility manager, a commercial HVAC technician, or someone who oversees a building's refrigeration systems, you've probably had those gut‑drop moments—where you realize a simple oversight just turned into a $2,000+ headache.

I've been handling service orders for Tecumseh equipment for over a decade. And I've made plenty of mistakes. So many that I started keeping a personal failure log (note to self: don't delete that spreadsheet). This article is that log, boiled down into a practical checklist. It covers five errors I've personally made, and the step‑by‑step process I now use to avoid them.

Total steps: 5. Each one addresses a specific pitfall that cost me time, money, or reputation.

Step 1: Don't Assume the Condensing Unit Is the Problem

Early in my career, I'd walk up to a Tecumseh condensing unit not running, check the power, and immediately swap the compressor. Twice. The second time was a $1,400 mistake.

Here's what I now check first:

• Power supply phase. On commercial jobs, single‑phase vs three‑phase errors happen more than you'd think.
• Control voltage. Low voltage due to a bad transformer will fool you.
• High‑pressure switch. Often tripped because someone blocked airflow (like stacking boxes against the unit).

I said "compressor's dead" to the client. They heard "we need a new unit." Result: they ordered a replacement before I even ran a proper diagnosis. Communication failure? Yep. (I still kick myself for that one.)

Step 2: Before Cleaning an Ice Machine, Check the Condenser Coils

Ice machine calls are frustrating. A client says the machine is making thin ice or no ice. My instinct used to be to dive into the water system—check the inlet valve, the dump valve, the evaporator plate. But the real culprit was often the air‑cooled condenser (usually a Tecumseh compressor unit).

Here's my current checklist:

• Visually inspect the coil. Look for dust, lint, or grease buildup.
• Clean with a soft brush or compressed air. I've used a Stihl leaf blower on outdoor condensers with great success (just keep the nozzle away from electrical panels).
• Measure the temperature difference across the coil. If more than 20°F, it's dirty.

One time I spent two hours troubleshooting a Manitowoc ice machine—replaced the water filter, cleaned the float—only to find the condenser fins were packed with grease from a nearby fryer. (Mental note: always check the environment first.)

Step 3: Use a Kerosene Heater with Care Near Refrigeration Units

In winter, especially with emergency commercial roof leak detection, you might need to thaw frozen pipes or keep a space warm while working. I once brought a kerosene heater into a mechanical room to keep my hands warm while diagnosing a Tecumseh condensing unit. The soot and combustion byproducts got sucked into the compressor's cooling airflow. It clogged the condenser coil within a week.

What I do now:

• Never operate a kerosene heater in the same room as condenser units for more than 10 minutes. If you must, position the heater far away and have ventilation.
• Check the condenser fins after any heat source use. Look for black deposits.
• Use electric heaters instead. Avoid the soot problem entirely.

I dodged a bullet when I caught the soot in time to clean it off the coil. But I still regret not thinking about it beforehand. (Worse than expected.)

Step 4: Don't Overlook Emergency Roof Leak Detection—Especially After Heavy Rain

You get an emergency call: water is dripping from the ceiling above the HVAC unit. The natural assumption is a refrigerant leak or a condensate pan overflow. But twice I've found the real cause was a roof leak that had nothing to do with the equipment.

Here's my pre‐inspection checklist:

• Check the roof membrane near the curbing of the condensing unit. Look for tears, standing water, or deteriorated flashing.
• Inspect the condensate drain. Yes, it's the first suspect. But if it's clear and still dripping, the water is likely from outside.
• Use a thermal camera or moisture meter. If you don't have one, borrow one. They're worth it.

I once spent three hours replacing a Tecumseh compressor (thinking a roof leak had caused a refrigerant line to burst) when it was just a seam in the roof itself. $1,800 extra labor and material. (I still kick myself for not looking up first.)

Step 5: When Quoting Replacement Parts, Always Be Transparent About What's Not Included

Here's where the transparency trust position kicks in. I've learned that hidden costs damage relationships more than a higher upfront price.

A contractor once ordered a Tecumseh replacement compressor from me. I quoted $1,100. He assumed that included the start kit, contactor, and freight. His total ended up $240 more. He wasn't happy—and he had every right to be annoyed.

My rule now:

• List every line item. Compressor, mounting kit, electrical components, core charge, shipping.
• Say out loud: "This price is the compressor only. Do you need anything else?"
• If they're comparing prices, ask what the other quote includes. Often it's the same base price but with 'extras' baked in.

The vendor who lists all fees upfront—even if the total looks higher—usually costs less in the end. (As of March 2025, I've seen this pattern hold true across multiple suppliers. Verify current prices, but the principle stays.)

Common Pitfalls to Avoid

• Assuming OEM always equals no issues. A Tecumseh OEM part is excellent, but compatibility matters. Check model numbers before ordering.
• Skipping the 'What's NOT included' question. Ask it every time. It's saved me more than any discount ever could.
• Relying on memory for diagnostic steps. Write it down. I printed a laminated checklist and keep it in my tool bag.

One of my biggest regrets: not documenting vendor verbal promises. If I'd gotten it in writing, we'd have had grounds to dispute the late fee. Now I keep a digital log (even just a shared Google Doc) for every major order. It's not glamorous, but it works.