What Is Infinite Resistance On A Multimeter?

On a multimeter, infinite resistance means the meter shows OL or a maxed-out value, signaling an open circuit with no path for current.

Seeing a multimeter flash OL, 1, — — —, or a tiny infinity icon can be puzzling the first time. The reading points to a break between your probes somewhere. No current can flow through an open path, so the meter cannot push test current and compute ohms. That condition is what users call “infinite resistance.”

What Infinite Resistance Means In Practice

Digital meters inject a small current and watch the voltage drop. If there is no conductive route, the drop never forms within the selected range. The display then signals an over-limit state. You will see this when the probes are in the air, across an open switch, or across a broken trace. On an analog meter, the needle stays parked at the left end of the ohms scale, which is the infinity end.

Manufacturers describe this as an overload or over-limit indication on the resistance function. You can read a clear summary in the DMM fundamentals from NI and in Keysight’s multimeter guide linked later in this article.

Common Displays For “No Path” Readings

Meter Type	What You See	Meaning
Digital, auto-range	“OL”, “1”, dashed lines, or ∞	Open circuit or above the present range
Digital, manual range	“OL” or “1” on low ranges	Increase the range to check for very high ohms
Analog multimeter	Needle stays at left on Ω scale	Infinity on the reverse-printed ohms scale

Understanding Infinite Resistance On A Multimeter: Real Uses

The “infinite” reading helps find breaks. A light that will not turn on can trace back to an open switch or a loose connector. A blower motor that will not start might hide a broken winding. With the circuit de-energized, placing the probes across a suspect path and seeing OL confirms that the path is open.

Open Circuit Vs Over Range

OL does not always mean the material truly blocks all current. It can also mean the resistance sits above the selected range. Auto-range meters jump ranges, yet some models still show OL briefly before settling. On a manual range, moving from, say, 200 kΩ to 20 MΩ can turn an OL into a number like 3.5 MΩ. Many vendor guides show the same behavior on both manual and auto-range meters.

Analog Vs Digital Behavior

Analog ohm scales run backward: zero at the right, infinity at the left. Touching the probes together drives the needle to the right. Separating the probes lets the needle relax to the far left, signaling no path. The All About Circuits lab notes describe this layout and show the needle motion on open and short readings.

Where This Reading Is Handy

Tracing a cut cable or a cracked PCB trace.
Checking a switch in the OFF position.
Confirming a blown thermal fuse or link.
Testing a relay coil for a break.
Spotting a sensor that has failed open.

Reading “Infinity” On A Multimeter: Common Causes

Plenty of everyday slips can trigger OL during a resistance test. Run through these before swapping parts.

Leads Not Touching The Circuit

A loose clip or a dull probe tip breaks contact. Re-seat the tip on clean metal. For plated boards, press lightly through any oxide. For wires, pierce the insulation only if you plan to seal the spot later.

Wrong Jacks Or Dial Position

Put the red lead in the Ω jack and the black lead in COM. If the red lead sits in a current jack, the resistance function will not behave. Set the dial to Ω, not to V or A. On auto-range meters, a separate continuity symbol selects the beeper mode; that mode still reflects an open path when silent.

Range Too Low

A high-value resistor, a damp surface, or a long cable can exceed a low range. Step up the range or use REL/zero to subtract stray lead resistance on very low readings. When your meter offers a max of 40 MΩ and the part is above that, the screen keeps showing OL because it cannot display the value.

Live Circuit

Ohms checks belong on de-energized gear. Power on a circuit drives current from the source and confuses the resistance function. Remove power, discharge caps, then measure. Fluke’s page on continuity testing echoes the same advice: test with power off, then read the result.

Component Still In Circuit

Parallel paths can mask a break and can also make a good part look open. If the reading seems off, lift one leg of the component and measure again. This isolates the part and gives a clean result.

Quick Tests To Confirm An Open Path

Use this short workflow to separate true opens from setup snags.

Short The Probes

Touch probe to probe. You should see near zero ohms or a beep in continuity mode. If not, inspect the leads for breaks and clean the tips. Try another set if you own a spare pair.

Range Up Or Down

If you see OL on a manual range, step up through the ranges until a number appears. If the number never appears and the part should conduct, the path is open. If you are chasing milliohms, step down and subtract lead resistance with REL.

Switch To Continuity

Continuity uses a threshold. A beep means the path is low enough. Silence means the path exceeds that threshold. The Fluke guide above explains the beep behavior and why silence maps to an open path.

Isolate The Test Point

Unplug connectors. Flip a switch to OFF. Lift one leg of a resistor or a link. Retest the point with fewer parallel routes. This keeps hidden paths from skewing the picture.

Cause	Fast Check	Next Move
Open component	OL on all ranges	Isolate one leg and retest; replace if still open
Range too low	OL only on low ranges	Select a higher range; read in megohms
Dirty probe or pad	Reading flickers with pressure	Clean, scrape lightly, or use clip leads
Wrong jack	No change when shorting probes	Move lead to Ω jack; retry the short test
Live circuit	Erratic numbers or auto power-off trips	Remove power and discharge; test again

Why “Infinite” Is Not A Number

Multimeters do not compute a literal infinity. OL is a flag that the meter cannot resolve a value within the selected limit. Keysight’s How to read a multimeter guide notes that OL or a lone “1” can mark an open path or an overload of the present range. Jumping ranges or using continuity mode tells you which case you have.

Typical Situations Where OL Is Normal

Not every OL points to a fault. Some checks expect it.

A switch in the OFF position.
A power cord unplugged from a device.
A fuse removed from a holder.
A sensor that only closes under pressure or heat.
Insulation tests across plastic, glass, or air gaps.

Fixes That Clear An Open Reading

Once you confirm a break, you can restore the path. Reseat a connector. Crimp or solder a split joint. Replace a blown link or a cracked resistor. Rebuild a corroded lug. Route a new section of wire if a cable jacket shows cuts or kinks. After each change, repeat the short test, then measure across the path again.

Meter Setup Tips That Keep Readings Clean

Use The Right Ports

Leave the red lead in the Ω jack for resistance and continuity. Move it to mA or A only when you plan to measure current, then move it back right after that task.

Keep Fingers Off The Metal

Skin can add a parallel path on high-ohm checks. Hold the insulated parts of the probes. Clip leads help when you need both hands elsewhere.

Zero Low-Ohm Work

Short the probes, press REL or short-zero if provided, then measure the low-value part. This removes lead resistance from the reading and avoids false opens on tiny values.

Mind Auto-Hold Or Min/Max

These features latch a reading. If OL latched by accident, clear the hold and retest. Many meters show a small icon when a capture feature is active.

Isolate Large Capacitors

Capacitors can charge from the meter’s source during ohms checks and mislead the display. Discharge them and test out of circuit when you can.

Analog Meter Notes

Before measuring, short the probes and use the ohms-adjust knob to set the needle to zero on the right side of the Ω scale. That sets the internal battery and balance. When the probes separate, the needle rests at the far left, which is the infinite end. If the needle never moves when shorted, the meter battery may be flat or the range switch may need cleaning.

Reading Components That Often Show OL

Resistors

A carbon film resistor that reads OL is likely cracked. If the color code says 1 MΩ and your meter tops out at 2 MΩ, read on the highest range. If you still see OL after lifting one leg, the part has failed.

Coils And Motors

Small coils measure in tens to hundreds of ohms. Large windings can run to a few kiloohms. OL on a coil across all ranges is a break in the wire. For motors, check across the thermal protector as well; that link can fail open.

Fuses And Links

A good fuse reads near zero and beeps. An open fuse reads OL. Check across the metal end caps, not across the glass. Some fuses look intact but still fail the continuity check.

Switches And Relays

Across the contacts, OFF reads OL and ON reads near zero. If ON still reads OL, the contacts are burnt or the mechanism is stuck. On a relay, confirm the coil first, then check the contacts while driving the coil from a safe source.

Why OL On Voltage Or Current Is A Different Story

On voltage or current ranges, OL means the measured quantity sits beyond the selected span. That message does not speak about continuity. Only the resistance or continuity functions can label a path as open. Always match the mode to the question you are asking.

When To Trust The Beep Instead Of The Number

Continuity mode places a threshold on the reading and gives an instant tone for a closed path. It saves time during tracing. A silent meter still means open. Fluke’s continuity page above spells out this behavior and gives safe test steps.

Field Scenarios And Meter Behavior

Say a doorbell quit working. Across the button you read OL with the button at rest, then near zero when pressed. That tells you the button still makes contact and the fault sits elsewhere. On a fridge with a no-cool complaint, an evaporator fan that reads OL across the coil tabs is a failed winding; swap the fan and you are back in business. On a guitar, a pickup that reads OL across its lead pair has a break in the fine wire. A new pickup or a careful rewind restores the tone.

Think about long outdoor runs. Measuring between two ends of a buried cable, OL suggests a cut. Probing each section where the cable surfaces narrows the break to a zone. In control panels, OL across a limit switch at rest is expected, while OL across a pushed stop button points to bad contacts. Across a heater element, OL hints at a blown thermal fuse tucked under the sleeve. Scenes like these teach a simple habit: let OL guide your touch of the probes.

Wrap-Up

Infinite resistance on a multimeter is a plain message: there is no usable path between your probes, or the resistance lies beyond the meter’s reach on the present range. Check your jacks and range, test with power off, isolate the part, and try continuity for a quick yes or no. With that sequence, OL turns from a mystery into a clear, helpful clue.