Klein Trade Program — Week 4
Multimeters, Wiring & Learning What the Number Actually Means
Saturday, May 2, 2026
HVAC Theory Certificate Program — Multimeters & Wiring
Welcome to Week 4 of the Klein Trade Program.
Week 1 introduced us to HVAC.
Week 2 started HVAC Theory and introduced the tools.
Week 3?
We lit the torches.
Week 4?
Time to break out the meters.
This is where HVAC starts getting interesting.
Because you can look at a wire all day long.
It isn’t going to tell you anything.
You can stare at a contactor.
You can stare at a capacitor.
You can stare at a motor.
Eventually you’re going to have to measure something.
And that’s what this week was about.
This Week: What Does the Number Mean?
There’s something important we want students learning from the beginning.
A multimeter doesn’t diagnose anything.
It gives you information.
That’s it.
The screen might say:
0
24
120
240
OL
Or some other number.
The meter did its job.
Now it’s your turn.
What does that number mean?
Where did you take the measurement?
What were you expecting?
What does the circuit tell you should be there?
Is the equipment energized?
Is the circuit open?
Is the circuit closed?
That’s the difference between taking a measurement and diagnosing a system.
Week 4 is where we started building that distinction.
What Are We Learning This Week?
Week 4 continued our HVAC Theory Certificate Program with two subjects that are going to follow these students throughout their entire careers:
Multimeters
and
Wiring
We introduced the meter itself.
We talked about basic electrical measurements.
We started looking at wiring.
And most importantly, we began connecting the two.
Because eventually the wiring diagram tells you what the circuit is supposed to do.
The meter helps you figure out what it’s actually doing.
That’s troubleshooting.
We’re not there yet.
But this is where it starts.
Meet the Multimeter
At first glance, a multimeter can look a little ridiculous.
Dial.
Buttons.
Symbols.
Leads.
Clamp.
Numbers.
More symbols.
And depending on the meter:
Approximately 37 functions you’re not going to use today.
😂
So we started with the basics.
What is the meter?
What can it measure?
Where do the leads go?
What does the selector do?
What does the clamp do?
What are we actually trying to find out?
Before somebody starts sticking meter leads into electrical equipment, they should understand the tool they’re holding.
And No, the Temu Meter Is Still Not the One
We covered this in our hand-tools article.
But since we’re actually talking about meters now, it’s worth repeating.
We saw it too.
Big screen.
Clamp.
Lots of buttons.
Looks professional.
$16.83.
Free shipping.
We’ve all thought about it.
😂
There are plenty of places to save money when you’re building your first HVAC tool bag.
The instrument you’re holding while testing energized electrical equipment probably isn’t where I’d start.
Use a quality meter appropriate for the work you’re performing.
Then learn how to use it correctly.
Because an expensive meter in untrained hands isn’t particularly useful either.
The tool doesn’t make the technician.
Understanding the measurement does.
Keep Learning
Our full Day-One HVAC tool guide covers meters along with the other essential tools a new technician needs:
HVAC Hand Tools: What You Actually Need on Day One →
And yes.
Buy the second 6-in-1.
Voltage
One of the first measurements we introduced was voltage.
At the beginner level, we want students to understand voltage as electrical potential between two points.
That’s important.
Because voltage isn’t something you measure by randomly touching your meter leads to things until numbers appear.
You’re measuring between two points.
Where are your leads?
What should the voltage be?
What does the reading tell you?
In residential HVAC, students are eventually going to encounter things like:
24 volts.
120 volts.
208/230 volts.
Different circuits.
Different purposes.
Different hazards.
Week 4 isn’t about memorizing every possible electrical scenario.
It’s about beginning to understand what you’re looking at.
Resistance
Then we have resistance.
Now we’re introducing ohms.
And this is where the meter starts becoming useful for understanding components and circuits when they’re properly de-energized and isolated as required for the measurement.
We’re beginning to ask questions like:
Is there a complete path?
Is something open?
What resistance are we measuring?
Again:
The important part isn’t getting a number.
It’s knowing what the number means.
Continuity
Continuity is one of those functions that’s incredibly satisfying when you’re brand new.
Touch the leads together.
BEEEEEEP.
😂
Great.
Everybody loves the beep.
But:
The beep is not a diagnosis.
Continuity simply helps us determine whether there’s a continuous electrical path under the conditions we’re testing.
That’s useful.
Very useful.
But we still have to understand the circuit.
Otherwise we’re just walking around making the meter beep at things.
Current
Now we get to use the clamp.
Current tells us about electrical flow through a conductor.
And this is another measurement students are going to use constantly as they progress.
Motors.
Compressors.
Blowers.
Condenser fan motors.
Heating elements.
Eventually those amperage readings become part of a much larger diagnostic picture.
For now?
Understand what we’re measuring and how the clamp is used correctly.
We’ll build from there.
Capacitance
If you’re going into residential HVAC service, you’re going to become very familiar with capacitance.
Very familiar.
😂
Capacitors are everywhere.
And eventually students will learn how to safely isolate and test them, compare the measurement to the component’s rating and determine whether it’s within the appropriate tolerance.
That’s coming.
Right now, we’re introducing the measurement.
Soon we’ll be changing them.
And someday you’ll be able to spot a swollen capacitor from across a driveway.
Welcome to residential HVAC.
Now Let’s Look at the Wiring
A meter without an understanding of the circuit is just a very expensive number generator.
So the other half of Week 4 was wiring.
We started getting comfortable with the idea that electrical circuits have paths.
Power comes from somewhere.
It travels through components.
Controls determine what happens.
Loads do work.
And eventually the circuit returns to its source.
That sounds simple.
Then somebody unfolds an HVAC wiring diagram for the first time.
What the hell is this?
😂
Lines.
Symbols.
Numbers.
Components.
Connections.
Welcome to wiring diagrams.
Follow the Circuit
Here’s one of the habits we want to build early:
Stop looking at the whole diagram at once.
Follow one circuit.
Where does power start?
Where does it go next?
What has to happen for it to continue?
What switch or control is involved?
What’s the load?
Where does the circuit end?
One piece at a time.
Suddenly the giant page full of lines starts becoming smaller circuits that actually make sense.
That’s the goal.
The Wiring Diagram Is Trying to Help You
New technicians sometimes look at wiring diagrams like the manufacturer included them as some sort of practical joke.
They didn’t.
😂
That diagram is one of the most useful things on the equipment.
It tells you how the system was designed to operate.
And later, when the system isn’t operating correctly, it gives you a roadmap.
The meter tells you what’s happening.
The diagram tells you what should be happening.
Put those together?
Now we’re getting somewhere.
Hands-On: Stop Being Afraid of the Meter
This was another week where physically handling the tool matters.
Pick up the meter.
Turn the dial.
Plug in the leads.
Look at the symbols.
Clamp around a conductor.
Take basic measurements in a controlled training environment.
Ask questions.
Get comfortable.
Because we don’t want the first time somebody really handles a meter to be when they’re standing in front of live equipment at a customer’s house.
This is what the shop is for.
Make mistakes here.
Ask the “dumb” question here.
Put the lead in the wrong port here and have somebody correct you before you’re in the field.
That’s training.
Stuff That Isn’t in the Manual
Don’t Pretend You Understand
Electrical is one of the worst places to pretend.
If you don’t understand something:
Say so.
If you don’t know where to put the meter leads:
Ask.
If you don’t understand why you’re taking the measurement:
STOP.
There is absolutely nothing impressive about confidently doing something you don’t understand around energized electrical equipment.
We’d much rather hear:
“I don’t know.”
Great.
Now we can teach you.
That’s why you’re here.
Stuff That Isn’t in the Manual — Don’t Chase Numbers
This is something technicians can struggle with even after they’ve been doing HVAC for a while.
Don’t just collect measurements.
Voltage.
Amps.
Resistance.
Capacitance.
Temperatures.
Pressures.
Superheat.
Subcooling.
Static pressure.
You can collect 100 numbers and still have no idea what’s wrong.
Before taking a measurement, eventually you should be able to answer:
“Why am I measuring this?”
What question are you trying to answer?
That’s diagnostic thinking.
We’re introducing that mindset now, even though the students don’t have enough knowledge yet to fully use it.
Because eventually we don’t want:
“The meter says 24.”
We want:
“I have 24 volts here, which tells me…”
That’s a technician.
Safety Isn’t a Separate Lesson
Electrical safety isn’t something we teach once and then check off the list.
It follows every electrical lesson.
Know whether the circuit is energized.
Use the correct meter setting.
Use properly rated equipment.
Understand where your hands are.
Understand where your leads are.
Don’t assume power is off because somebody told you it was.
Verify.
And don’t take measurements you don’t understand just because somebody on the internet did it in a video.
Know what you’re doing and why you’re doing it.
What Should a Student Know After Week 4?
We’re not expecting anybody to troubleshoot a complicated electrical problem after one Saturday.
We’re building skills.
By the end of Week 4, students should be more comfortable with:
- Identifying the basic parts of a multimeter
- Understanding basic meter functions
- Understanding the purpose of voltage measurements
- Understanding resistance and continuity at an introductory level
- Understanding current measurements with a clamp meter
- Recognizing capacitance as an important HVAC measurement
- Beginning to understand basic wiring
- Following simple electrical paths
- Looking at wiring diagrams without immediately panicking
- Understanding that a measurement needs context
- Knowing when to stop and ask a question
Most importantly:
The meter should look a little less like a mysterious box full of symbols than it did at the beginning of class.
That’s progress.
The Meter Gives You a Number. You Give It Meaning.
That’s really the Week 4 lesson.
Anyone can buy a meter.
Anyone can put leads on something.
Anyone can read the number on the screen.
The trade is understanding:
Why did I take this measurement?
What did I expect?
What did I actually get?
What does that tell me?
We’re nowhere near mastering that yet.
But this is where it begins.
Week 1, these guys were staring at an air conditioner like:
“Okay…”
Week 3, they were holding torches.
Now they’re holding meters.
We’re moving.
One Saturday at a time.
See You in Week 5
We’re documenting the Klein Trade Program week by week inside A/C University.
The goal isn’t just to show a list of classes.
We want prospective students to see what learning a trade actually looks like.
We want customers to see what we’re teaching.
And eventually we want the technical lessons from these Saturdays to become an HVAC curriculum anyone can follow through A/C University.
Some weeks will have deeper lessons linked.
Some won’t yet.
As we build them, everything will start connecting.
For now:
Learn the meter.
Learn the circuit.
And please…
Close Temu.
😂