Introduction: What Does “OL” Mean on a Multimeter?

If your digital multimeter suddenly shows “OL”, “0L” or an infinity symbol (∞), don’t panic — it usually means the meter is reading an open circuit or a value beyond its measurement range. ✔️

“OL” stands for Open Loop. This message appears in several modes, but it does NOT always mean something is broken. This guide explains exactly what “OL” means, why it appears, and how to fix it depending on the mode you’re using. ??

What OL Means in Different Multimeter Modes

1️⃣ OL in Resistance Mode (Ω)

If your meter shows “OL” while measuring resistance, it means:

• There is no electrical connection between the probes
• The circuit is open
• The resistance is higher than the meter can measure

For example:

• Testing across a broken wire → OL
• Testing a blown fuse → OL
• Testing a switch in the OFF position → OL

2️⃣ OL in Continuity Mode ?

Continuity mode checks if two points are connected. “OL” means: No continuity

• No beep
• Open circuit
• Broken wire or bad connection

This is normal behavior when the circuit is not closed.

3️⃣ OL in Voltage Mode (V)

If you see “OL” in AC or DC voltage mode, it usually means:

• The voltage is too high for the selected range (manual range meters)
• You’re using the wrong input port
• The meter auto-protection is activated

This can happen when testing high-voltage lines or industrial equipment. ⚡

4️⃣ OL in Current Mode (A)

Seeing “OL” in current mode may indicate:

• The current exceeds the fuse rating
• The internal fuse is already blown
• The leads are in the wrong ports

If your meter shows “OL” but nothing is being measured, the fuse is likely blown. ?

Common Causes of “OL” Readings

Depending on what you’re testing, “OL” usually appears due to one of these reasons:

• ? The circuit is open or disconnected
• ? A fuse inside the multimeter is blown
• ? The probes are not touching the right points
• ⚡ The selected range is too low
• ? Wire or PCB track is broken
• ? Component has failed (open circuit)
• ? User is testing incorrectly

How to Fix “OL” on a Multimeter

✔ Step 1: Check Probe Placement

Make sure your probes are firmly touching the correct test points.

✔ Step 2: Switch the Range (If Manual Range Meter)

Select a higher range if the reading exceeds the meter’s limit.

✔ Step 3: Test a Known Good Component

To confirm if the meter is working properly, test:

• A resistor
• A metal object (continuity)
• A battery (voltage)

✔ Step 4: Check the Meter Fuse

If current mode shows “OL”, the fuse is likely blown. Replace the internal fuse with the correct rating.

✔ Step 5: Inspect the Component Under Test

If wires, fuses, switches or tracks show “OL”, they are probably broken and need replacement.

When “OL” Means Danger

Be careful — sometimes “OL” appears because the voltage is too high or unstable.

• ⚡ High-voltage sources
• ⚡ Faulty industrial equipment
• ⚡ Incorrect meter range settings

If you suspect high voltage, STOP testing immediately. Safety first. ?

Common Mistakes Leading to OL

• ❌ Trying to measure resistance on a live circuit
• ❌ Using continuity mode instead of resistance
• ❌ Blown meter fuse from incorrect current measurement
• ❌ Expecting continuity where none should exist
• ❌ Measuring current through voltage ports

Final Thoughts

“OL” on a multimeter isn’t usually a fault — it’s the meter telling you there’s an open circuit or a value out of range. ✔

Understanding what “OL” means in each mode will help you troubleshoot safely and accurately. Use this guide as your quick reference whenever you see “OL” on your screen. ??

Next: Learn why multimeter fuses blow and how to avoid damaging your meter. ?