Interactive Solar Diagnostic Tool for PWM Controllers
SafeGuard Survey: Understanding your vessel, ensuring your safety.
WHY: This tool is specifically designed for PWM (Pulse Width Modulation) charge controllers. It will guide you through diagnosing a complete failure, pinpointing an underperforming part of your solar array, and identifying wiring issues.
HOW: You will need a multimeter. Simply enter your system's details in Stage 1. Then, follow the guided tests in the subsequent stages, entering your measurements to receive an instant, tailored diagnosis.
Stage 1: Enter Your System Details
Stage 2: Your System's Calculated Target
Based on your inputs, here is the approximate Open Circuit Voltage (Voc) for your array. Use this as a baseline for the first test.
Target Array Voltage (Voc)
Stage 3: Test the Array (Open Circuit)
The Key Test: Turn your array's isolator switch OFF. Use a multimeter to measure the DC voltage on the terminals on the **panel side** of the switch.
Pro Tip: How to Get a Stable Reading
Wait for clouds to pass and ensure steady sunlight. Take the highest, most stable reading you observe.
Performance Check:
Your measured voltage of V is the expected target of V.
Stage 3a: Pinpointing the Array Fault
Step 1: Check Fuses. The most common cause of a partial failure is a blown inline fuse. Check the fuse for each of your parallel strings.
Step 2: Test Strings. If fuses are good, test the Open Circuit Voltage (Voc) of each panel/string individually at the combiner box.
Stage 4: Isolating the Fault (Switch or Controller?)
Test Under Load (PWM Logic)
Crucial Step: Turn the isolator switch back **ON**. Because you have a PWM controller, you should expect the high panel voltage to be pulled down to match the battery voltage when the system is operating.
Measure the voltage on **both sides** of the isolator switch:
- The Panel-Side terminals.
- The Controller-Side terminals.
Why this check is important: A high-resistance connection (like a corroded MC4) will pass the Open Circuit test in Stage 3, but when the controller tries to pull current, the voltage across that bad connection collapses. We must rule this out.
Please perform the physical check below:
- Disconnect: With the solar isolator OFF, safely disconnect each MC4 connector in the array.
- Inspect: Look for any signs of green or white corrosion on the metal pins.
- Tug Test: Gently but firmly tug on the cable where it enters the back of the MC4 connector to ensure it is secure.
Fault Found!
Repair the connection (re-crimp or replace connector) and then restart this diagnostic to confirm the system is working.
Connections Verified
Since the wiring is good, the fault lies further down the line. Proceed to the final verification check below.
Stage 5: Final Verification Before Replacement
Instruction: We need to check the fuse and connection between the controller and the battery. Keep the solar isolator switch **OFF**.
- Place your multimeter's black probe on the battery's main negative terminal.
- Place the red probe on the terminal on the **battery-side** of the controller's main fuse holder. Note the voltage.
- Move the red probe to the terminal on the **controller-side** of the fuse holder.
You should expect to see a reading close to your initial battery voltage of on both sides of the fuse.
Need Professional Advice?
This diagnostic tool provides an excellent starting point. For a detailed assessment of your vessel's specific needs or to book a survey, please get in touch.