Multimeter Shows "OL" or Overload Error: Complete Troubleshooting

You’re measuring with your multimeter and instead of a number, the display shows “OL,” “OVERLOAD,” or just “1” (sometimes with decimal points like “1. “). This is one of the most common and confusing multimeter errors. The good news: it’s rarely a problem with the meter itself. This comprehensive guide explains what “OL” means, why it happens in different measurement modes, and how to fix it.

Table of Contents

🔍 Quick Diagnosis: Why Does Multimeter Show “OL”?

“OL” or overload can appear in any measurement mode, with different meanings:

Measurement Mode	“OL” Meaning	Most Common Cause	Fix Difficulty
Voltage	Voltage exceeds selected range	Range too low (2V range, measuring 12V)	Easy
Resistance	Resistance too high or open circuit	Testing open/broken circuit (correct)	Easy
Current	Current exceeds range OR blown fuse	Blown fuse (very common)	Easy
Continuity	No connection/open circuit	Wire broken or not touching (correct)	Easy
Capacitance	Capacitor too large for range	Range too low or shorted cap	Easy
Diode Test	Wrong polarity or open diode	Diode reversed or failed open	Easy

📊 What Does “OL” Actually Mean?

Display variations for overload:

Different multimeters show overload differently:

“OL” – Most common (stands for “OverLoad” or “Over Limit”)
“1” or “1. “ – Left-most digit only, with or without decimal points
“—-“ – Dashes (some older meters)
“OVERLOAD” – Full word (some meters)
“___” – Blank with flashing display
“Err” – Error message (less common)

What it tells you:

Reading is beyond the meter’s measurement capability
Could be too high, too low, or open circuit (depending on function)
Not necessarily a problem – often indicates correct measurement

Understanding “out of range”:

Each measurement function has limits:

Voltage: 0V to 1000V (typical max)
Resistance: 0Ω to 20-60MΩ (typical max)
Current: 0A to 10A or 20A (typical max)
If measured value exceeds limit → displays “OL”

Range selection matters:

Manual ranging meters have multiple ranges per function
Each range has upper limit
If value exceeds that specific range → “OL”
Solution: Select higher range

⚡ Problem #1: “OL” When Measuring Voltage

What’s happening:

Voltage exceeds the selected range on your meter. You’re trying to measure 120V on the 20V range, for example.

How to diagnose:

Measuring known voltage source shows “OL”
Meter is on DC voltage or AC voltage mode
Display shows “OL” immediately when probes touch
Other functions (resistance, continuity) work fine

Solution:

For manual-ranging meters:

Increase the voltage range:

Look at dial position
Typical DC voltage ranges:
- 200mV (0.2V)
- 2V
- 20V
- 200V
- 1000V
Select higher range than expected voltage:
- Measuring 9V battery → use 20V range
- Measuring 12V car battery → use 20V range
- Measuring 120V outlet → use 200V or 750V range
- Measuring 240V appliance → use 750V or 1000V range

Example scenario:

Dial set to: 2V range
Measuring: 9V battery
Display: “OL” (9V exceeds 2V range limit)
Fix: Rotate dial to 20V range
Display now: 9.1V ✓

Start high, work down strategy:

If unsure of voltage, start with highest range (200V or 1000V)
Measure – get reading
If reading very small (like “0.012V” on 200V range)
Work down to lower range for better resolution
Stop when you get good readable number

Range selection guide:

Expected Voltage	Select Range
1.5V (AA battery)	2V or 20V
5V (USB)	20V
9V (9V battery)	20V
12V (car battery)	20V or 200V
24V (thermostat)	200V
48V (telecom)	200V
120V (US outlet)	200V or 750V
240V (appliance)	750V or 1000V
480V (3-phase)	1000V

For auto-ranging meters:

Auto-ranging should prevent “OL” but…

If shows “OL” on auto-range:
- Voltage exceeds meter’s absolute maximum (usually 600V or 1000V)
- This is dangerous – stop immediately
- Verify what you’re measuring
- May need high-voltage probe (10:1 or 100:1 divider)
Check meter specifications:
- Look at meter face or manual
- Maximum voltage clearly marked
- Never exceed this voltage
- Exceeding max voltage can:
  - Damage meter
  - Cause electric shock
  - Create arc flash
  - Destroy internal protection
Verify auto-range is enabled:
- Some meters have manual override
- Button or switch to enable/disable auto-ranging
- If accidentally in manual mode, may show “OL”

Auto-range troubleshooting:

Turn meter off and on (reset)
Remove and reinsert battery
Check if “AUTO” appears on display
If auto-range not working → use manual mode

Special case: Voltage reading fine, then shows “OL”:

This indicates:

Voltage was within range
Then exceeded range (spike, surge, or source changed)
OR probe lost contact momentarily

What to do:

Re-measure
If consistent “OL” → voltage increased or source changed
If intermittent “OL” → poor connection or noise

🔴 Problem #2: “OL” When Measuring Resistance

This is often NOT a problem – it’s telling you the circuit is OPEN.

What’s happening:

Either the resistance is higher than the selected range, or there’s no connection (open circuit). “OL” in resistance mode usually means infinite resistance = open circuit.

How to diagnose:

Testing wire, resistor, or component
Display shows “OL” immediately
Other functions work fine
Meter is in resistance (Ω) mode

When “OL” is CORRECT (not a problem):

Testing for open circuits (intentional):

Examples where “OL” is expected:

Testing broken wire: “OL” confirms wire is broken ✓
Testing open switch: “OL” confirms switch is off/open ✓
Testing diode in reverse: “OL” is correct (diodes block one direction) ✓
Testing capacitor initially: “OL” then slowly drops (charging) ✓
Testing air gap: “OL” between separated probes ✓
Testing failed open fuse: “OL” confirms fuse blown ✓

This is the meter doing its job:

Infinite resistance = open circuit = “OL”
This is useful information, not an error

Testing very high resistance:

Components with very high resistance:

High-value resistors (1MΩ – 10MΩ+)
Insulation (should be >10MΩ)
Capacitors (after full charge)
Transistor junctions (depending on biasing)

If measuring high resistance:

Check meter’s maximum resistance range
Typical: 20MΩ, 40MΩ, or 60MΩ max
If component resistance exceeds this → “OL”
This is normal – resistance truly higher than meter can measure

When “OL” is a PROBLEM (need to fix):

Cause 1: Range too low

For manual-ranging meters:

Selected range lower than resistance value
Example: 200Ω range, measuring 10kΩ resistor = “OL”

Solution:

Select higher resistance range
Typical ranges:
- 200Ω
- 2kΩ (2,000Ω)
- 20kΩ (20,000Ω)
- 200kΩ (200,000Ω)
- 2MΩ (2,000,000Ω)
- 20MΩ or 40MΩ (highest)
Start with highest range, work down for better resolution

Example:

Measuring 10kΩ resistor
200Ω range → “OL”
2kΩ range → “OL”
20kΩ range → “10.1” (correct!) ✓

Cause 2: Poor probe contact

Symptoms:

“OL” flickers to reading and back
Pressing harder shows reading
Wiggling probes changes between “OL” and reading

Solutions:

Clean probe tips:
- Use fine sandpaper (400-600 grit)
- Remove oxidation until shiny
- Or use contact cleaner
Clean component/test point:
- Remove oxidation, paint, coating
- Fresh solder joint preferred
- Scrape PCB traces gently if oxidized
Press probes firmly:
- Ensure good metal-to-metal contact
- Hold steady during measurement
Check probe tips:
- Not damaged or worn
- Sharp tips make better contact
- Replace if broken

Cause 3: Testing in-circuit (other paths)

Problem:

Measuring resistor that’s soldered in circuit
Other components provide parallel paths
Measured resistance lower OR higher than expected
May show “OL” if parallel paths all very high resistance

Solution:

Best: Unsolder one leg of component
Test component out of circuit
Or disconnect from circuit completely
This isolates component for accurate reading

Cause 4: Measuring powered circuit

NEVER measure resistance on powered circuit:

Voltage present prevents accurate reading
May show “OL” or nonsense value
Can damage meter
Can damage circuit

Solution:

Turn off power to circuit
Discharge capacitors (if present)
Wait 30 seconds for residual voltage to dissipate
Then measure resistance

Cause 5: Body resistance affecting measurement

On very high resistance measurements:

Your body resistance (skin to skin) ≈ 1-10MΩ
Touching both probes with fingers creates parallel path
Meter measures your body instead of component
May show lower than expected or “OL” if fingers dry

Solution:

Use insulated probe tips only
Don’t touch bare metal of probes
Use alligator clips or test leads for high-impedance measurements
Keep hands dry

Auto-ranging in resistance mode:

If auto-range meter shows “OL”:

Resistance genuinely higher than meter’s maximum (20-60MΩ)
Open circuit (infinite resistance)
Poor contact
Check: Are you expecting a low resistance?
- If yes → check connections
- If measuring insulation → “OL” is good (high resistance)

🔌 Problem #3: “OL” When Measuring Current

This is usually a blown fuse – very common problem!

What’s happening:

Either current exceeds range, meter is in wrong mode, OR (most common) the internal fuse is blown. Current measurement is the #1 cause of blown fuses.

How to diagnose:

Measuring current shows “OL”
Or shows very low reading (0.001A when expecting 1A)
Recently measured current or tested short circuit
Meter was accidentally used to measure voltage in current mode
Voltage and resistance measurements still work fine

Cause 1: Blown fuse (MOST COMMON – 80% of cases)

Why fuses blow in current mode:

Accidentally measured voltage in current mode
Connected meter in parallel (across) instead of series (in-line)
Short circuit or overload current
Exceeded 10A on mA setting

How to tell fuse is blown:

“OL” when measuring any current
Or very low current reading (microamps when expecting amps)
Voltage and resistance still work
Recent incident (spark, pop, or wrong measurement)

Solution: Check and replace fuse

Access fuses:

Turn off meter and remove test leads
Open back case:
- Usually 2-4 Phillips head screws
- Carefully separate front and back
- May need to slide apart
Locate fuses:
- Typically 2 fuses (ceramic cylinders with metal caps)
- mA/μA fuse: 200mA-500mA (small current)
- A fuse: 10A-20A (high current)
Which fuse to check:
- If using mA/μA jack → check mA fuse
- If using 10A/20A jack → check A fuse

Test fuse:

Visual inspection:
- Look through transparent/translucent body
- Should see thin wire inside
- If wire broken or discolored → blown
Continuity test (if you have second meter):
- Set second meter to continuity/resistance
- Touch probes to both fuse ends
- Should read 0Ω or beep
- If “OL” or no beep → blown

Replace fuse:

Identify correct fuse rating:
- Printed on fuse body (e.g., “F500mA 250V”)
- Or check meter manual
- Match rating exactly:
  - Current rating (200mA, 500mA, 10A, etc.)
  - Voltage rating (250V, 1000V)
  - Type: Fast-blow (F) or Time-delay (T)
Where to buy:
- Electronics stores (Digi-Key, Mouser, Micro Center)
- Hardware stores (sometimes)
- Online (Amazon – search “multimeter fuse 500mA”)
- Meter manufacturer
Cost: $1-5 per fuse
NEVER:
- Use higher current rating (defeats protection)
- Use aluminum foil or wire (fire/explosion hazard)
- Leave fuse out (unsafe)

Common fuse specifications:

Fuse Type	Rating	Size	Use
mA fuse	200mA-500mA	5×20mm	Low current (mA/μA jack)
A fuse	10A-11A	10×38mm	High current (10A/20A jack)
Voltage	250V-1000V	–	Must match or exceed

After replacing fuse:

Reassemble meter carefully
Test on known current source
If blows again immediately → internal short (meter damaged)

Prevent future blown fuses:

Always verify mode before connecting
Current = series (in-line with circuit)
Voltage = parallel (across component)
Start with 10A jack if current unknown
Don’t exceed meter’s current rating

Cause 2: Wrong jack for current range

Multimeters typically have 2 current jacks:

mA/μA jack: For small currents (0-200mA or 0-500mA)
10A/20A jack: For large currents (0-10A or 0-20A)

Problem:

Measuring 5A current
Leads plugged into mA jack (only rated 500mA max)
Display shows “OL” (5A exceeds 500mA range)
Fuse may blow!

Solution:

Move RED lead to 10A jack
Rotate dial to 10A or A range
Both must match:
- 10A jack + 10A dial position ✓
- mA jack + mA dial position ✓
- 10A jack + mA dial position ✗ (wrong)
- mA jack + 10A dial position ✗ (may blow fuse)

Jack selection guide:

Expected Current	Use Jack	Set Dial To
<200mA (0.2A)	mA/μA	mA range
200mA-10A	10A	10A or A
>10A	Can’t measure directly	Need clamp meter

Cause 3: Current exceeds meter capability

Meter limits:

Most handheld meters: 10A or 20A maximum
Often time-limited (10A for 30 seconds max)
Continuous use may be limited to 3A-5A

If measuring >10A:

Display shows “OL”
This is correct – meter protecting itself
Don’t force it – can damage meter

Solutions for high current:

Use 10A jack and range (if <10A)
Use clamp meter for currents >10A:
- Clamp meters measure up to 400A-1000A
- Non-contact measurement (safer)
- Cost: $30-200
Use current shunt + voltage measurement:
- 100A shunt = 50mV per 100A (typical)
- Measure voltage across shunt
- Calculate current: I = V / R
Use in-line current sensor:
- Hall effect sensors
- Output voltage proportional to current

Cause 4: Measuring AC current instead of DC (or vice versa)

Problem:

Dial set to DC current (A-)
Measuring AC current source (A~)
May show “OL” or very low reading

Solution:

Switch to correct mode:
- DC current: A-, DCA (batteries, DC power supplies)
- AC current: A~, ACA (AC outlets, motors, transformers)
Some meters have separate positions
Others use button to toggle

Cause 5: Connected in parallel instead of series

Most common current measurement mistake:

WRONG (parallel connection):

[Power Supply +] ────┬──── [Load] ──── [Power Supply -]
                     │
                [Multimeter]
                     │
                    └──────────────────────────────────

Meter connected across load (like voltage measurement)
Creates short circuit through meter
Blows fuse immediately
May show “OL” if fuse blown or before blowing

CORRECT (series connection):

[Power Supply +] ── [Multimeter] ── [Load] ── [Power Supply -]

Meter inserted in current path
Break circuit, insert meter in-line
Current flows through meter

How to measure current correctly:

Turn off power
Break circuit at one point
Insert meter in the break (in series)
Connect:
- Meter COM to one side of break
- Meter A to other side of break
Set meter:
- Current mode (A)
- Correct range (start with 10A if unsure)
- Correct jack (10A for >200mA)
Turn on power
Read current

🔊 Problem #4: “OL” in Continuity Mode

This usually means “OPEN CIRCUIT” – which is often correct!

What’s happening:

Continuity mode tests if two points are electrically connected (low resistance path). “OL” means no connection or very high resistance.

When “OL” is correct (expected):

Testing for opens (breaks in circuit):

Testing unplugged cord: “OL” at break point = found problem ✓
Testing broken wire: “OL” confirms wire is cut ✓
Testing switch (off position): “OL” = switch is open ✓
Testing blown fuse: “OL” = fuse is blown ✓
Testing relay (not energized): “OL” between NC terminals ✓

Examples where “OL” is good information:

Wire test:
[Probe] ───── Wire OK ───── [Probe]  → Beeps (continuity)
[Probe] ──X── Wire Broken ── [Probe]  → "OL" (open) ✓ Found problem!

When “OL” is a problem (unexpected):

Cause 1: Poor probe contact

Symptoms:

Intermittent “OL” and beeping
Changes when you press harder
Was beeping, now “OL”

Solutions:

Clean probe tips (sandpaper)
Clean test points
Press probes firmly
Check probe tips not damaged

Cause 2: Resistance too high for continuity

How continuity mode works:

Tests if resistance below threshold (typically 30-200Ω)
Below threshold → Beeps + shows resistance
Above threshold → “OL” + no beep

Problem:

Testing circuit with 500Ω resistance
This is “continuous” electrically
But exceeds continuity threshold
Shows “OL” even though path exists

Solution:

Switch to resistance (Ω) mode
Measure actual resistance
500Ω is low enough for most circuits
Continuity mode just too sensitive for this circuit

When continuity threshold matters:

Most wiring: <1Ω (continuity should beep)
Long wires: 1-10Ω (may or may not beep)
Circuit traces: <0.1Ω (should beep)
Resistive paths: >50Ω (probably “OL” in continuity)

Cause 3: Capacitor in circuit

Problem:

Testing circuit with capacitor
Initial reading: “OL” (cap charging)
Then beeps as cap charges
Then “OL” again

This is normal:

Capacitor blocks DC (appears as open initially)
Capacitor charges through meter’s test current
While charging, appears as low resistance (beeps)
Fully charged, appears as open (“OL”)

Solution:

Discharge capacitor first
Or remove capacitor from circuit
Or switch to resistance mode (shows charging behavior clearly)

Cause 4: Diode in circuit (one direction)

Problem:

Testing circuit containing diode
One direction: Beeps
Reverse probes: “OL”

This is normal:

Diodes conduct one direction only
Forward: Low resistance (beeps)
Reverse: High resistance (“OL”)

Solution:

This confirms diode is working correctly
Not a problem, just how diodes work
If beeps both directions → diode shorted (failed)

🔋 Problem #5: “OL” When Measuring Capacitance

What’s happening:

Capacitor value exceeds selected range, capacitor is open (failed), or capacitor is charged and needs discharge first.

Cause 1: Range too low

Manual ranging meters:

Selected range lower than capacitor value
Example: 2μF range, measuring 100μF cap = “OL”

Solution:

Select higher capacitance range
Typical ranges:
- 20nF (0.02μF)
- 200nF (0.2μF)
- 2μF
- 20μF
- 200μF
- 2000μF or 20mF
Read capacitor marking to estimate range needed

Capacitor markings:

104 = 100,000pF = 100nF = 0.1μF
10μF = 10μF (direct marking)
100μF 25V = 100μF capacitance, 25V rating

Cause 2: Capacitor charged

Problem:

Capacitor has voltage across it
Meter tries to measure but voltage interferes
Shows “OL” or incorrect value

Solution: Discharge capacitor first

For small caps (<10μF):
- Short leads with insulated screwdriver
- Brief spark is normal
For large caps (>10μF):
- Use resistor to discharge (1kΩ-10kΩ, 5W)
- Touch resistor leads to cap terminals
- Wait 5-10 seconds
- Check voltage with meter (should be <1V)
For very large caps (>1000μF):
- Use 100Ω resistor or 12V light bulb
- Lamp will light briefly as cap discharges
- Wait until lamp goes dark
Then measure capacitance

Cause 3: Capacitor failed open

Capacitors can fail:

Electrolytic caps especially prone to failure
Fail open (infinite capacitance = 0 capacitance)
Fail short (zero resistance)

If “OL” in capacitance mode:

May indicate failed open capacitor
Confirms capacitor needs replacement
This is useful diagnostic information

How to verify:

Measure resistance: Should show high resistance (>100kΩ)
If low resistance (<100Ω) → shorted
If “OL” in both capacitance and resistance → definitely open/failed

Cause 4: Wrong polarity (electrolytics)

Polarized capacitors (electrolytic, tantalum):

Have positive and negative terminals
Must be inserted correctly into meter

Some meters require correct polarity:

Red probe to positive terminal
Black probe to negative terminal
Backwards may show “OL” or wrong value

Solution:

Check capacitor markings:
- Negative stripe on one side
- Or + symbol near positive lead
- Longer lead is positive (new caps)
Connect red to positive, black to negative
Measure again

Cause 5: Capacitor too large for meter

Meter limitations:

Budget meters: 20μF-200μF maximum
Mid-range: 200μF-20,000μF maximum
High-end: Up to 100mF (100,000μF)

If capacitor exceeds maximum:

Shows “OL”
This is correct – meter can’t measure that large
Need specialized capacitance meter or LCR meter

🔌 Problem #6: “OL” in Diode Test Mode

What’s happening:

Diode test mode applies small voltage and measures current flow. “OL” in one direction is normal (diodes block reverse current). “OL” in both directions means open diode or wrong test method.

When “OL” is correct (normal diode behavior):

Diodes conduct one direction only:

Forward direction: Shows voltage drop (0.3-0.7V typically)
Reverse direction: Shows “OL” (blocked)

Testing diode correctly:

Normal Diode:
Forward:  Meter shows 0.5-0.7V (silicon diode)
Reverse:  Meter shows "OL" ✓ This is correct!

Failed Diode:
Both directions: "OL" = Open (failed)
Both directions: 0V = Shorted (failed)

LED voltage drops (higher than regular diodes):

Red LED: 1.8-2.2V
Green LED: 2.0-3.0V
Blue/White LED: 3.0-3.5V
If “OL”: May need resistance mode (LED drops >meter’s test voltage)

When “OL” is a problem:

Cause 1: Wrong polarity

Solution:

Reverse probe connections
Red to anode (+), black to cathode (-)
Should show voltage drop
If still “OL” both directions → diode failed open

Cause 2: Diode failed open

Symptoms:

“OL” in both directions
No voltage drop either way

This confirms:

Diode is defective
Needs replacement
“OL” is useful diagnostic information

Cause 3: Testing in-circuit

Problem:

Other components provide parallel paths
Meter measures multiple components at once
May show “OL” if parallel paths all high resistance

Solution:

Unsolder one lead of diode
Test out of circuit
More accurate measurement

Cause 4: LED requires more voltage than meter provides

Problem:

Some meters provide 1.5V test voltage
Blue/white LEDs need 3.0-3.5V
Meter’s voltage insufficient to light LED
Shows “OL”

Solution:

Not really a problem – LED is fine
Use resistance mode (may show resistance value)
Or use higher-voltage diode tester
Or simply test by connecting to appropriate voltage source

📋 Step-by-Step Troubleshooting by Function

For Voltage showing “OL”:

✅ Check if voltage exceeds range – increase range
✅ Verify voltage doesn’t exceed meter max (600V/1000V)
✅ Check auto-range is working (turn off/on meter)
✅ Test with different voltage source
✅ If exceeds meter capability – need high-voltage probe

For Resistance showing “OL”:

✅ First: Is circuit actually open? (This may be correct!)
✅ Increase range if manual ranging
✅ Clean probe tips and test points
✅ Press probes firmly for good contact
✅ Verify power off in circuit being tested
✅ Test out of circuit if possible
✅ If measuring insulation – “OL” is good (high resistance)

For Current showing “OL”:

✅ Check fuse first – 80% chance it’s blown
✅ Verify leads in correct jacks (10A jack for >200mA)
✅ Verify dial matches jack (10A position with 10A jack)
✅ Confirm connected in series, not parallel
✅ Check current doesn’t exceed 10A meter capability
✅ Verify DC/AC mode matches source
✅ Replace blown fuse if found

For Continuity showing “OL”:

✅ First: Is circuit actually open? (May be correct!)
✅ Clean probe tips
✅ Press probes firmly
✅ Check if resistance above continuity threshold (switch to Ω mode)
✅ Discharge capacitors in circuit
✅ Check for diodes (one direction may be “OL” normally)

For Capacitance showing “OL”:

✅ Discharge capacitor first
✅ Increase range if manual ranging
✅ Check polarity (electrolytics)
✅ Verify capacitor value doesn’t exceed meter maximum
✅ If “OL” in both capacitance and resistance – capacitor failed open

For Diode Test showing “OL”:

✅ First: Check reverse direction too (OL in one direction is normal!)
✅ Reverse probe polarity
✅ If “OL” both directions – diode failed open (this is useful info!)
✅ Test out of circuit if in-circuit measurement
✅ For LEDs – may need resistance mode instead

🔑 Key Takeaways

“OL” is NOT always a problem:

Resistance mode: “OL” = open circuit (often what you’re testing for)
Continuity mode: “OL” = no connection (often expected)
Diode test: “OL” in reverse = normal diode behavior
Capacitance: “OL” = failed open capacitor (diagnostic information)

“OL” IS a problem when:

Voltage mode: Range too low or voltage exceeds meter capability
Current mode: Blown fuse (most common) or wrong jack/range
Expecting continuity but get “OL”: Poor contact or broken connection

Most common causes by function:

Function	#1 Cause of “OL”	Fix
Voltage	Range too low	Select higher range
Current	Blown fuse	Replace fuse
Resistance	Open circuit	Often correct – verify if expected
Continuity	Open circuit	Often correct – verify if expected
Capacitance	Range too low or cap failed	Increase range or replace cap

Quick fixes:

Voltage: Increase range (start with highest)
Current: Check/replace fuse, verify 10A jack
Resistance/Continuity: Check probe contact, verify circuit is actually closed
Capacitance: Discharge cap first, increase range
Diode: Reverse probes, check both directions

Prevention tips:

Start with highest range when value unknown
Use auto-ranging to avoid “OL” errors
Check fuse regularly if measuring current
Always verify mode before connecting
Understand “OL” meaning varies by function

💡 Understanding “OL” is Key to Using Multimeter

“OL” is communication from your meter:

“The value is beyond what I can measure in this mode/range”
Sometimes means “infinite” (open circuit)
Sometimes means “too high for selected range”
Sometimes means “internal protection activated”

Learn to interpret “OL” in context:

What are you measuring?
What did you expect to see?
Is “OL” plausible for this measurement?

Examples:

Testing wire continuity, get “OL” → Wire is broken ✓
Testing 9V battery, get “OL” → Range too low ✗
Testing blown fuse, get “OL” → Fuse is blown ✓
Testing current, get “OL” → Meter fuse blown ✗

The more you use your meter, the more “OL” becomes useful information rather than a confusing error!

💬 Still Seeing “OL”?

If you still see “OL” after trying solutions:

Verify what you’re measuring:
- Is the value truly within meter’s capability?
- Are you using correct function and range?
- Is the circuit actually open (and “OL” is correct)?
Test meter on known good source:
- Voltage: Test fresh 9V battery (should read 9.0-9.6V)
- Resistance: Test known resistor (read color code)
- Continuity: Short probes together (should beep)
- Current: May need test circuit setup
Check meter specifications:
- Maximum voltage, current, resistance ratings
- May need different meter for your application
Consider meter upgrade:
- Higher maximum ranges
- Auto-ranging (prevents range errors)
- Better suited to your work
Consult meter manual:
- “OL” may have special meaning on your specific meter
- Some meters display “OL” for battery low warning
- Error codes may resemble “OL”

In most cases, “OL” is either correct information (open circuit) or easily fixed (wrong range, blown fuse, poor contact). Understanding what it means in each mode is the key to effective troubleshooting!