Low Solar Panel Output Troubleshooting with UNI-T UT381PV Malaysia

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Low solar panel output does not automatically mean that the photovoltaic panel is defective. Reduced generation may be caused by changing sunlight, high panel temperature, shading, dirt, incorrect installation angle or an electrical fault.

The UNI-T UT381PV Solar Irradiance Meter helps technicians separate environmental and installation factors from potential PV system problems.

Confirm the Available Solar Irradiance

Start by measuring the solar irradiance reaching the panel surface.

The UT381PV measures from 0 to 1400 W/m². Position the sensor in the same plane as the solar panel and ensure that it is not shaded by the technician, test equipment or nearby structures.

If irradiance is low, reduced solar output may be expected. Possible environmental causes include:

Cloud cover
Haze
Early-morning or late-afternoon sunlight
Temporary shading
Rain or high atmospheric moisture
Incorrect sensor positioning

Do not compare the panel output with its rated power without considering the actual irradiance during the test.

Check for Partial Shading

Even a small shadow can affect the output of a panel or an entire solar string.

Inspect for shadows caused by:

Trees and vegetation
Antennas
Water tanks
Roof structures
Nearby buildings
Accumulated leaves
Maintenance equipment
Other rows of solar panels

Measure irradiance at several positions when uneven sunlight is suspected. A significant difference between locations may indicate partial shading across the array.

Measure the Panel Temperature

Solar panels can become much hotter than the surrounding air during strong sunlight.

Use the supplied surface-temperature probe to measure the panel temperature while recording the ambient condition. High panel temperature can reduce voltage and overall power output.

A system showing strong irradiance but lower-than-expected power may therefore be affected by heat rather than a defective panel.

For a useful record, note:

Solar irradiance
Panel surface temperature
Ambient temperature
PV voltage
PV current
Measurement time
Weather condition

These values should be recorded at approximately the same time.

Inspect Dirt and Surface Contamination

Dust, bird droppings, leaves and other contamination can block sunlight from reaching the solar cells.

Before cleaning, record the irradiance and electrical output. After the panel has been cleaned safely, repeat the measurement under similar sunlight conditions.

An improvement after cleaning can help confirm that surface contamination was contributing to the low output.

Do not compare readings taken under significantly different weather conditions because the result may be misleading.

Verify the Panel Inclination

The UT381PV measures inclination from −90° to +90°.

Check whether the panel angle matches the project design and whether adjacent panels have been installed consistently. A panel with an incorrect tilt may receive less solar energy during certain periods of the day.

Also inspect the mounting structure for:

Loose fasteners
Shifted brackets
Uneven panel alignment
Roof movement
Installation differences between rows

Inclination measurement is especially useful when one section of the solar array performs differently from another.

Confirm the Azimuth Direction

The UT381PV provides azimuth measurement from 0° to 360°.

Use it to verify the direction in which the panel is facing. Incorrect orientation may reduce solar exposure during the most productive hours.

For more reliable azimuth readings:

Complete the compass calibration
Keep away from strong magnetic sources
Avoid measuring directly beside large metal objects
Allow the reading to stabilise
Repeat the measurement for confirmation

When the Environment Is Not the Cause

If the irradiance, panel temperature, inclination and azimuth readings are reasonable but the electrical output remains low, the system may require additional electrical testing.

Possible causes include:

Loose MC4 connector
Damaged PV cable
Incorrect string connection
Panel mismatch
Failed bypass diode
Insulation problem
Inverter fault
Defective solar module

The UT381PV cannot directly measure all electrical faults. A suitable PV multimeter, insulation tester, clamp meter or I-V curve analyser may be required for further diagnosis.

The UT381PV can also be integrated with the UNI-T UT541 15kW Photovoltaic I-V Curve Analyzer for more detailed PV performance testing.

Use Data Logging for Intermittent Problems

The UT381PV stores up to 12,800 sets of data, with recording intervals from one second to 60 minutes.

Data logging is useful when output changes only at certain times of the day. Technicians can compare irradiance and temperature trends against the PV system’s generation record.

This can help identify problems associated with:

Moving shadows
Afternoon overheating
Intermittent cloud cover
Changing panel orientation relative to sunlight
Differences between morning and afternoon performance

Bluetooth connection to the UNI-T iENV mobile application also supports convenient review of measurement records.

A Practical Troubleshooting Sequence

For low solar panel output, follow this sequence:

Inspect the panel and surrounding area.
Measure the available solar irradiance.
Check for partial shading.
Record ambient and panel temperatures.
Verify the panel inclination.
Confirm the azimuth direction.
Compare the environmental readings with electrical output.
Continue with electrical testing if the output remains abnormal.

This approach reduces the risk of replacing a solar panel before confirming whether the real cause is environmental, installation-related or electrical.

For assistance selecting the UNI-T UT381PV for solar panel installation and troubleshooting in Malaysia, contact MTM Precision.

MTM Precision Sdn Bhd
Showroom & Service Centre: No. 29-1 & 29-2, Jalan Bandar 18, Pusat Bandar Puchong, 47160 Puchong, Selangor, Malaysia
Tel: 03-8080 7172
WhatsApp: +6016-660 7346
Email: mtmpre@yahoo.com
Website: www.mtmpre.com.my

Low Solar Panel Output Troubleshooting with UNI-T UT381PV Malaysia