Battery Voltage Above Controller Upper Limit
What does PERKINS-168-3 mean?
The PERKINS-168-3 (Kohler RDC2) diesel fault code means: Battery Voltage Above Controller Upper Limit. This is a moderate severity code.
Common Symptoms
- Panel displays fault code 168-3 and triggers a warning alarm
- Yellow or amber warning light stays on during engine run
- Battery voltage reading on the controller display climbs above 15V (12V system) or 30V (24V system)
- Generator may continue to run but logs the fault in its fault history
- External battery charger feels unusually hot or shows a fault light of its own
- Lights or accessories powered from the generator battery appear brighter than normal
- Controller intermittently resets or reboots during a run cycle
Probable Causes (Ranked by Likelihood)
- Faulty or unregulated external battery charger outputting voltage above the set threshold Very Likely
- Failed or stuck-open alternator voltage regulator on the engine-mounted charging alternator Very Likely
- Wiring fault creating a false high voltage reading at the controller battery sense input Likely
- Incorrect battery charger float voltage set too high for the installed battery bank Likely
- Failed battery unable to absorb charge current, causing voltage to spike (sulfated or open-cell battery) Possible
- Controller battery sense wire shorted to a higher voltage supply rail Possible
- Software or configuration error with controller voltage threshold set too low for the application Less Likely
Step-by-Step Diagnostic Procedure
Step 1. With the engine stopped, measure DC voltage directly at the battery terminals using a multimeter. A healthy fully charged 12V battery reads 12.6V to 12.8V at rest. A 24V system should read 25.2V to 25.6V. If the resting voltage already exceeds 13.5V (12V system) or 27V (24V system), your external charger may be the culprit.
Step 2. Check your external battery charger, if one is fitted. Look for a float or absorption voltage setting dial or DIP switches on the charger. Confirm the float voltage is set to 13.5V to 13.8V for 12V systems or 27V to 27.6V for 24V systems. Reset if it is higher. Replace the charger if it has no adjustment and is reading high.
Step 3. Start the engine and let it idle. Measure DC voltage at the battery terminals again while the engine runs. Voltage should rise to roughly 13.8V to 14.4V on a 12V system. If it climbs above 15V and keeps rising, the engine-mounted charging alternator regulator is likely failed. Note this reading and shut down.
Step 4. Inspect the wiring from the battery positive terminal back to the controller battery sense input (typically a small-gauge wire labeled B+ or BATT+ on the controller harness). Look for chafe points, bare wire contacting a higher-voltage rail, or corrosion creating a false voltage rise. Repair any damage found.
Step 5. Check the battery itself. A badly sulfated or internally open battery cannot absorb charge current normally, which can drive terminal voltage high even from a correctly set charger. If the battery is more than four years old, test it with a battery load tester or take it to an auto parts store for a free load test. Replace it if it fails.
Step 6. If you have access to Perkins EST (Electronic Service Tool) or the PowerWizard 1.1/2.0 controller display, navigate to the battery voltage parameter and compare the live reading shown on the controller to your multimeter reading at the battery. If the controller reads significantly higher than the multimeter, the sense wiring or controller input is the problem, not the actual battery voltage.
Step 7. Clear the fault code using the controller STOP or RESET button (refer to your PowerWizard panel label), then restart and monitor. If 168-3 returns immediately with a confirmed high voltage from your multimeter, proceed to replace the external charger or charging alternator regulator. If the multimeter shows normal voltage but the code returns, have a technician inspect the controller sense circuit or recalibrate the threshold using Perkins EST.
Frequently Asked Questions
What does Perkins code 168-3 mean?
It means the controller measured the battery voltage rising above its upper programmed limit. On a 12V system that limit is typically around 15V, and on a 24V system it is around 30V. The most common reasons are a faulty external battery charger set too high or a failed voltage regulator on the engine's own charging alternator.
Can my generator still run with this code?
Usually yes, at least in the short term. Code 168-3 is a warning, not a hard shutdown fault on most PowerWizard and FG Wilson controller configurations. However, running with consistently high battery voltage will damage the battery, the controller, and any DC-powered accessories over time. Diagnose and fix it as soon as practical.
How much does it cost to fix?
If the problem is just the external float charger, a replacement quality charger runs $50 to $150 and you can swap it yourself in about 30 minutes. If the engine charging alternator regulator has failed, parts are $80 to $200 and a technician will typically charge $150 to $300 in labor. Full pro diagnosis and repair is generally $150 to $600 depending on what failed.
Will the generator start the next time the power goes out?
Most likely yes. Code 168-3 is a warning-level fault and does not block an emergency start on typical PowerWizard controller setups. The bigger risk is that if the high voltage has damaged the battery, the battery may fail to crank the engine when you need it most. Check the battery condition as part of your diagnosis so you are not caught off guard during an outage.