Battery Charging Voltage Above Upper Limit
What does MAGNUM-5 mean?
The MAGNUM-5 (Magnum) diesel fault code means: Battery Charging Voltage Above Upper Limit. This is a moderate severity code.
Common Symptoms
- Fault code 5 appears on the Magnum CONNECTED controller LCD or operator panel LED fault display on older units
- Tower shuts down or refuses to start after displaying the fault
- Battery feels warm or hot to the touch even after the engine has been off for a while
- Battery terminals show white or bluish corrosion buildup more than usual
- Lights flicker or act erratic before the fault trips
- You notice the external battery charger was left plugged in while the engine was also running
- Unit alarms and will not reset even after cycling the panel to OFF and back to RUN
Probable Causes (Ranked by Likelihood)
- External battery charger left connected while engine is running, stacking voltage on top of the alternator output Very Likely
- Faulty engine alternator voltage regulator stuck in full-field, pushing charge voltage above the controller threshold (typically above 15.5V DC on a 12V system) Very Likely
- Failed or shorted alternator diode pack causing uncontrolled charging output Likely
- Loose or corroded battery negative ground connection causing a false high-voltage reading at the controller sense circuit Possible
- Controller battery voltage sense wire chafed against a positive source, feeding artificially elevated voltage to the input Possible
- Battery internally shorted, dropping internal resistance so the alternator drives voltage up unchecked Less Likely
- Controller voltage sense calibration drifted, triggering fault at normal charge voltage Less Likely
Step-by-Step Diagnostic Procedure
Start with the obvious. Check whether an external battery charger is plugged into the battery. If yes, disconnect it completely, clear the fault on the Magnum CONNECTED controller LCD or operator panel LED fault display on older units, and try restarting. If the fault does not return, that was your problem.
Measure battery voltage at the battery terminals with a multimeter while the engine is running at normal operating speed. A healthy 12V system should read between 13.2V DC and 14.8V DC. If you see 15.5V DC or higher, the alternator or its regulator is overcharging.
If voltage is high, shut the engine down and inspect the engine alternator for obvious damage, burnt smell, or melted wiring near the alternator output terminal. On Kubota D902 and D1105 engines, the alternator is belt-driven off the front of the engine and is easy to access.
Check the alternator drive belt tension and condition. A slipping belt can cause inconsistent charging and odd voltage spikes. The belt should have about 10-12mm of deflection under moderate thumb pressure midspan. Replace if cracked or glazed.
Inspect the battery ground cable at both ends, at the battery negative terminal and at the engine block ground point. Clean any corrosion with a wire brush. A poor ground can cause the controller sense circuit to read artificially high voltage.
Trace the controller battery voltage sense wire (usually a small-gauge wire running from the controller board to the battery positive terminal or fuse block). Look for chafing, pinch points, or contact with other positive wires. Repair any damaged insulation.
If alternator output voltage is confirmed high and the regulator is internal to the alternator, the alternator assembly will need to be replaced or rebuilt. This is a moderate job on these machines but does not require specialty tools beyond basic hand tools and a multimeter. If you suspect the controller sense circuit or calibration, contact a Magnum-authorized service dealer for recalibration or board inspection.
Frequently Asked Questions
What does Magnum code 5 mean on a light tower?
Code 5 means the controller measured battery charging voltage above its upper limit, usually above 15.5V DC on a 12V system. The most common reason is an external battery charger left connected while the engine is also running. The second most common reason is a stuck alternator voltage regulator pushing charge voltage too high.
Can the light tower still run with code 5 active?
It depends on the unit. Some Magnum towers will log the fault and continue operating in a limited state, while others will shut down to protect the battery and electrical system. Either way you should not ignore it. Sustained overcharge can damage the battery and the controller itself.
How much does it cost to fix Magnum code 5?
If the fix is simply unplugging an external charger, it costs nothing. Cleaning corroded cables and checking belt tension is a DIY job under $20 in materials. A replacement alternator for the Kubota D902 or D1105 typically runs $150-$250 in parts, plus $75-$150 in shop labor if you go to a dealer.
Will the light tower start again after I clear code 5?
Yes, once you address the root cause and clear the fault on the panel, the unit should restart normally. If the fault returns immediately after clearing, the alternator regulator or sense wiring problem is still active and needs to be fixed before the tower will stay running reliably.