Magnum MS and ME Series Inverter Troubleshooting: Status LEDs and Fault Codes
Magnum MS and ME series inverter/charger troubleshooting
This guide covers the green status LED on Magnum MS series (pure sine wave: MS2000, MS2012, MS2812, MS2024, MS4024, MS4048) and ME series (modified sine wave: ME2012, ME2512, ME3112) inverter/chargers, and the fault messages shown on the ME-RC and ME-ARC remote controls. It is based on the official owner's manuals, now published on dmx-power.com (the former Magnum Dimensions website redirects there). The MS-PAE models have their own owner's manual, which is not covered here.
Safety first
- These inverters produce lethal 120 VAC and connect to battery banks that can deliver very high current.
- Switch off and disconnect both the AC input (shore power, generator) and the DC battery supply before any inspection or work. Magnum's maintenance section says to switch off both AC and DC circuits before performing any checks.
- There are no user-serviceable parts inside. Board replacement and internal repairs should be done by a qualified technician.
Status LED on the inverter: MS series
Watch the green charging/inverting LED next to the power button for at least 10 seconds before deciding what it shows.
| Code | Meaning | What to check |
|---|---|---|
| Off | The inverter is off, and there is no AC power at the output. If the LED stays off after you press the ON/OFF button, the unit has a fault: low battery, high battery, overload, over-temperature or internal fault. | See "LED off: fault conditions" below. |
| Slow flash (4 seconds on, 4 seconds off) | Float charging. AC input power is passing through to the loads. | Normal. |
| Medium flash (once every 2 seconds) | Inverting: running the loads from the battery. | Normal. |
| Fast flash (once per second), no AC input | Searching: waiting for a load at or above the Search Watts setting (default 5 W). | Turn on a load larger than 5 W, or turn off Search with a remote. |
| Fast flash (once per second), AC input connected | Absorb charging. AC input power is passing through to the loads. | Normal. |
| Very fast flash (flutters) | Equalize charging (only if enabled from a remote), or the inverter is continuously resetting. | If no one started an equalize charge from a remote, the inverter is probably in reset. Follow the reset steps below. |
| On (solid) | Bulk charging. AC input power is passing through to the loads. | Normal. |
Status LED on the inverter: ME series
| Code | Meaning | What to check |
|---|---|---|
| Off | The inverter is off, and there is no AC power at the output. If the LED stays off after you press the ON/OFF button, there is a fault (low battery, high battery, overload, over-temperature or internal fault). | See "LED off: fault conditions" below. |
| Slow flash (4 seconds on, 4 seconds off) | Float charging. AC input power is passing through to the loads. | Normal. |
| Medium flash (once per second), no AC input | Inverting, or searching for a load (default Search Watts setting: 5 W). | If there is no output, turn on a load larger than 5 W, or turn off Search with a remote. |
| Medium flash (once per second), AC input connected | Absorb charging. AC input power is passing through to the loads. | Normal. |
| Fast flash (flutters) | Equalize charging (only if enabled from a remote), or the inverter is continuously resetting. | If equalize was not started, do an inverter or power reset. If the fault continues, the unit needs service. |
| On (solid) | Bulk charging. AC input power is passing through to the loads. | Normal. |
LED off: fault conditions (no remote connected)
| Code | Meaning | What to check |
|---|---|---|
| Inverter switched off | The inverter is simply off. | Press the ON/OFF button lightly. It is a small momentary switch, so do not press hard. |
| Low battery | Battery voltage stayed below the Low Battery Cut Out (LBCO) setting for more than one minute. The default LBCO is 10.0 VDC (12 V models), 20.0 VDC (24 V) or 40.0 VDC (48 V), with an immediate cutout at 8.5 / 17.0 / 34.0 VDC. | Check fuses, breakers and cable connections. Measure the battery voltage at the inverter terminals and charge the batteries. The fault clears when the voltage rises to the Low Battery Cut In (LBCI) level, 12.5 / 25.0 / 50.0 VDC, or when AC power is connected and charging begins. |
| High battery | Battery voltage went above the High Battery Cut Out (HBCO) level. The inverter restarts by itself when the voltage drops to the High Battery Cut In (HBCI) level. | Usually caused by another charging source (alternator, solar, other chargers). Reduce or turn off the other charging sources. |
| Over-temperature | The internal temperature went above safe limits, usually from too much load or poor ventilation. The unit restarts by itself after it cools down. | Reduce the load. Check that cool air can flow through the inverter and that the vents are not blocked. |
| AC overload | The loads are larger than the inverter's output capacity, or the output wiring is shorted. | Reduce the AC loads, or remove all AC output wiring, then restart the inverter. |
| Internal fault | The inverter detected an internal fault and needs a reset. | Remove DC power, or hold the power button for about 15 seconds (see the reset steps below). If the fault does not clear, the unit needs service. |
Fault messages on the ME-RC and ME-ARC remotes
When the red FAULT LED on the remote lights, the display shows a fault message. Many faults clear by themselves once the cause is gone. Some need a manual restart: press and release the ON/OFF INVERTER button on the remote. If a fault still will not clear, do an inverter reset or a power reset (steps below).
| Code | Meaning | What to check |
|---|---|---|
| AC Backfeed | AC voltage from an outside source was detected on the inverter's AC output. Needs an inverter reset or power reset. | Recheck all wiring so the incoming hot and neutral wires cannot connect to the AC output. |
| AC Overload | The AC load exceeded the inverter's current protection limits. Under 10 seconds, the unit restarts by itself. Over 10 seconds, it shuts down and needs a manual restart. | Reduce the loads. Check for a short or incorrect wiring on the output, then restart manually. |
| Breaker Tripped | The inverter's AC input breaker opened from too much current flowing through to the loads. | Reduce the AC loads, then push in the input breaker to reset it. |
| Dead Batt Charge | The unit is trying to charge but sees less than 9 V (12 V models), 18 V (24 V) or 36 V (48 V): the bank is deeply discharged or not connected. | Compare the voltage at the inverter's DC terminals with the voltage at the battery. They should be within 0.5 VDC. If not, check all connections and the DC fuse or breaker. |
| FET Overload | The temperature of the internal FETs rose abnormally fast. Needs a manual restart. | Let the unit cool, then restart. If it returns, do an inverter reset. If it continues, disconnect the AC output wires and do a power reset. If it still does not clear, the inverter needs service. |
| High Battery | Battery voltage is above the HBCO value. It clears by itself once the voltage drops 0.3 VDC (12 V), 0.6 VDC (24 V) or 1.2 VDC (48 V) below HBCO. | Turn off any other charging source (solar, alternator, other charger) so the voltage can drop. |
| High Batt Temp | The battery temperature sensor (BTS) is above 54°C (129°F). It restarts by itself once the sensor cools to 49°C (120°F) or lower. | Make sure the BTS is not near a heat source and the batteries are not overheating. If the reading stays high, unplug the BTS. If the reading goes to 25°C (77°F), replace the BTS. If not, check the BTS port or have the inverter serviced. |
| High Speed Bus (ME-ARC) | Communication error between the inverter's internal microprocessors. | Do an inverter reset or power reset, then turn the inverter on. If it does not clear, the inverter may need service. |
| High Volts AC | Very high AC input voltage (above 150 VAC) was detected, so the charger or AC input is disabled. | Remove all AC input power for at least 15 minutes to clear it. Make sure only 120 VAC is connected to each AC input. |
| Low Battery | Battery voltage stayed below the LBCO setting for more than one minute. Shown only while inverting or searching. | Charge the batteries. It clears by itself when the battery voltage reaches 12.5 / 25.0 / 50.0 VDC (12 / 24 / 48 V models), or when AC power is connected and charging begins. |
| Overcurrent | Shutdown to protect internal power components, often from an excessive AC load. Under 10 seconds, the unit restarts by itself. Over 10 seconds, it needs a manual restart. | Reduce the loads. Check for a short or incorrect output wiring, then restart manually. If it continues, do an inverter reset. |
| Overtemp | The internal FETs and/or transformer went above their safe temperature range. Clears by itself after cooling. | If it happens while inverting, reduce the load. If it happens while charging, lower the charge rate. If it happens often, check for a hot location, poor ventilation, or cooling fans that are not working. |
| Stuck Relay | The internal AC pass-through relay is closed while the unit is inverting (it should be open). Needs an inverter or power reset. | The relay contacts are probably damaged. They are rated for 30 A AC continuous and should be protected by an input breaker of 30 A or less. Turn off large inductive loads (pumps, motors) before removing the AC source. |
| Tfmr Overtemp | The transformer temperature cut-out opened to protect the power transformer. Restarts by itself after cooling. | If it keeps happening, disconnect all AC output wires and reset the inverter. If it still does not clear, the inverter may need service. |
| StackClock Fault | A stacking cable problem, or one stacked inverter is losing sync with the other. | Use a genuine Magnum stacking cable (it is not a phone/data cable). Unplug and reconnect both ends until they click. If an accessory is plugged into the Stack port on a non-stacked system, do an inverter reset. |
| Stack Mode Fault | The other stacked inverter has a problem. | Check the other inverter for a fault. This clears once that fault is fixed. |
| StackPhase Fault | Incorrect AC input wiring, a lost input phase, a bad internal transfer relay, or an open AC input breaker. | Check those four items. If the fault does not clear, do an inverter reset. |
| Internal Bridge | The FET bridge shut down after inverting. The output circuit no longer detects any AC output voltage or current. | Do an inverter or power reset, then turn the inverter on. If the fault stays or returns, the inverter needs repair. |
| Internal Charger | The FET bridge shut down because the charger was trying to deliver full current but saw no rise in battery current or voltage. | Do an inverter or power reset. If the fault stays or returns, the inverter needs repair. |
| Internal NTC | The internal temperature sensor (NTC) reported a very large, unexpected temperature change. | Do an inverter or power reset. If the fault stays or returns, the inverter needs repair. |
| Internal Relay | The internal AC transfer relay is not closed while charging. | Do an inverter or power reset. If the fault stays or returns, the inverter needs repair. |
| Unknown Fault ## | The inverter sent a fault code that the remote cannot identify. | Note the number and contact technical support. |
ME-RC remote LEDs
- PWR (green): on = AC power (from the inverter, shore or generator) is present at the inverter's AC output. Off = the inverter is disabled, the remote is in Power Saver mode (press any button), the remote has no power, or there is no AC at the output.
- FAULT (red): on = a fault was detected. Read the message on the display.
- CHG (green): on = bulk, absorb, float or equalize charging. Blinking with "Charger Standby" = the charger was disabled with the ON/OFF CHARGER button. Blinking with "Full Charge" or "Silent" = Battery Saver mode. Blinking during a charge stage = charge current reduced because the inverter is hot or the AC input voltage is low. Blinking with no charge status = AC voltage detected on the input.
- INV (green): on = inverter enabled (supplying AC, or in Inverter Standby if CHG is also on). Blinking = Search mode (the load is below the Search Watts setting).
Charger will not start on shore or generator power
- If the CHG LED on the remote is not blinking, the charger does not accept the incoming AC. Measure the AC at the inverter input terminals: it should be 120 VAC ±20 VAC. Check that the VAC Dropout setting is 80 VAC or less.
- If the CHG LED is blinking, the transfer relay should close within 20 seconds and charging should start.
- If the transfer relay keeps closing and opening, the AC voltage is too low or dropping briefly. Try a VAC Dropout setting of 60 VAC. If cycling continues, lower the Charge Rate. Also check that the inverter's AC output is not wired back to its AC input.
- If charge current is low or zero, measure the input AC voltage. Charge rate is reduced to keep the input above 90 VAC. Also check the Shore Max and Charge Rate settings.
How to reset a Magnum inverter
Inverter reset ("soft reset"):
- Remove all AC power (shore power or generator) from the inverter. Magnum warns that resetting with AC connected may cause damage.
- Press and hold the inverter's Power ON/OFF button for about 15 seconds, until the status LED comes on and flashes rapidly.
- Release the button. The status LED goes off.
- Press the Power ON/OFF button to turn the inverter back on.
Power reset ("hard reset"), if the inverter reset does not work:
- Open the inverter's positive DC disconnect, or disconnect the positive battery cable. Do not remove any negative DC connection until all positive connections are off.
- Make sure the inverter and the remote are disconnected from all AC and DC power. The remote display should be blank.
- Wait 30 seconds, then reconnect the DC. A small spark when reconnecting the positive cable without a DC disconnect is normal, because the internal capacitors are charging.
If an internal fault does not clear after a reset, the inverter needs repair.
Replacement boards and parts for Magnum inverters
We stock replacement boards for MS and ME series inverters. Match the part number on your existing board or your exact inverter model before ordering. Board replacement should be done by a qualified technician.
- MS series control boards: TCB-MS2012, TCB-MS2812, TCB-MS4048, TCB-MS4448AE, TCB-MS4024PAE
- MS series FET boards: TFB-MS2000 / TFB-MS2012, TFB-MS4448PAE
- AC boards: TACB-ME/MS, TACB-MS-E, TACB-MSPAE, TACB-ME2000
- Filter boards: FB-MS/12, FB-MS-24, filter board for MS-AE and MS-PAE models
- ME series boards: TCB-ME2512 control board, tested FET board for ME2512, ME2000, ME2012 and RD2212
- Cooling fans: replacement fan A88-3203 (pack of 2)
- Remotes: ME-RC50, ME-ARC50
Owner's manuals for these products are listed on our Manuals and datasheets page.
Still not working? Contact our repair service — we repair marine inverter/chargers.
Source: MS Series Owner's Manual (64-0007, DMX Power); ME Series Owner's Manual (64-0002 Rev D, Sensata/Magnum Energy); ME-RC Remote Control Owner's Manual (64-0003, V2.9, DMX Power); ME-ARC Advanced Remote Control Owner's Manual (64-0030 Rev F, Magnum Energy).