Symptoms
- Display is blank or shows a low-battery symbol
- Reading shows zero or 'OL' when a value is expected
- Readings seem inconsistent or fluctuate randomly
- Meter worked fine before but now gives odd results
Likely causes
- CommonDead or weak internal batteryA low battery is the most common reason for a blank or erratic display.
- CommonBlown internal fuse (common after measuring current incorrectly)Accidentally measuring current in the wrong mode or range can blow the meter's protective fuse.
- CommonWrong function or range selected on the dialReading voltage while set to resistance mode, for example, gives a meaningless result.
- PossibleWorn, broken, or poorly connected test leadsFrayed leads or a loose connection at the meter body causes intermittent or false readings.
- Less commonMeter probes not making good contact with the test pointsCorrosion or a poor connection at the test point itself can look like a meter fault.
What to do
- Replace the internal battery, referring to the manual for the correct type and access panel.
- Check whether the display shows 'OL' or a fuse warning, which usually points to a blown internal fuse; check and replace it if accessible.
- Confirm the dial is set to the correct function (voltage, resistance, continuity, current) and appropriate range for what's being measured.
- Inspect the test leads for cracks, fraying, or a loose fit at the meter's input jacks.
- Test the meter on a known reference, like a fresh AA battery on the voltage setting, to confirm it reads correctly.
- Clean the probe tips and the test points on the circuit to ensure a solid connection.
- Replace the meter if it still won't read accurately after a fresh battery, fuse, and leads, since internal circuitry faults usually aren't user-repairable.
Tools and parts
- Replacement battery
- Replacement fuse (correct rating)
- Known reference source (battery)
Replacement multimeterSearch: “digital multimeter”
When to call a pro
Not typically a professional repair; multimeters are inexpensive enough that replacement is usually more practical than internal repair.
Safety
Use caution
Never measure voltage while the meter is set to current or resistance mode; this can blow the fuse or damage the meter and pose a shock risk.