I'm dealing with a frustrating issue on my 2017 Prevost coach equipped with an Outback VFX2812M inverter/charger system. The unit appears to be getting power since the cooling fan kicks on and runs, and when connected to shore power, 120VAC passes through just fine. However, when I disconnect from shore power and shut down the generator, the inverter completely fails to produce any AC power output.
What's particularly concerning is that the MATE digital controller inside the coach never powers on - the display remains completely blank with no indicator lights whatsoever. I have a brand new 12VDC battery bank, so I don't believe it's a battery issue. I've already tried disconnecting both AC and DC connections and reconnecting them, but aside from the fan running for about a minute during startup, nothing else happens.
I'm wondering if there might be internal fuses within the VFX2812M that I should be checking, and also whether the blank MATE controller display might be related to the same underlying problem. What are the most likely culprits when you have fan operation but no inverter function and no controller display?
Check internal DC fuse first - common failure point. Located inside inverter behind front panel. Also verify battery voltage at inverter terminals and check MATE controller cable. No display with fan running often indicates blown DC fuse or control board failure.
Your 2017 Prevost's Outback VFX2812M inverter/charger is experiencing a complete DC-side failure despite having a new 12V battery and working pass-through AC power. The fact that your digital controller inside the coach never powers on with a blank display is the key diagnostic clue here. Yes, there are internal fuses you should check - the VFX2812M has internal DC protection fuses located inside the unit (see manufacturer specifications for exact type and rating) that commonly blow and cause exactly these symptoms. However, before accessing internal fuses, you need to check the external DC disconnect fuse first, which is typically a 150-200 amp ANL or MEGA fuse between your battery bank and the inverter. The brief fan operation you mentioned suggests the unit is getting some power but shutting down on fault protection.
The VFX2812M's complete DC failure with working AC pass-through indicates a problem in the inverter's DC input section rather than the AC components. This commonly occurs when DC input fuses blow due to initial power surges, battery connection issues, or internal component failures. The digital controller receives its power from the inverter's DC section, so when those internal circuits fail or fuses blow, the controller goes completely dead.
Your disconnecting and reconnecting AC and DC power was the right troubleshooting step, but if internal DC fuses are blown, this won't restore function. The momentary fan operation suggests the unit attempts to initialize but immediately shuts down when it detects the DC fault condition. Outback inverters have robust protection circuits that will shut down the entire DC section if they detect problems, even if the AC pass-through continues working normally.
Step 1: Safety First - Turn off all AC and DC power sources. Disconnect shore power, shut down generator, and turn off the main DC disconnect switch. WARNING: High-amperage DC systems can produce lethal voltages and dangerous arc flash. Verify zero voltage at the inverter terminals with your multimeter before proceeding.
Step 2: Check External DC Fuse - Locate the large DC disconnect fuse (usually 200-250 amp ANL or MEGA) between your battery bank and inverter DC input. This fuse is often mounted in a separate fuse block near the batteries or inverter. Test continuity across the fuse - if it's blown, replace it and determine why it failed before powering up.
Step 3: Access Internal Fuses - Access to internal DC fuses in the VFX2812M requires significant disassembly beyond the front panel. Consult the service manual for proper disassembly procedures and fuse locations. These are the main DC input protection fuses that commonly fail.
Step 4: Test and Replace Internal Fuses - Use your multimeter to test continuity across each internal DC fuse (see manufacturer specifications for exact ratings). If either shows no continuity, replace both fuses even if only one appears blown (blown fuses often indicate stress on the entire DC protection circuit). Clean the fuse holders with contact cleaner and ensure tight connections.
Step 5: Verify DC Connections - While you have access, inspect all DC connections inside the inverter for corrosion, looseness, or heat damage. Clean and tighten as needed. Check that your battery bank voltage at the inverter DC terminals reads 12.6-14.4 volts (depending on charging state).
Step 6: Power Up Test - Reinstall the cover, turn on DC disconnect, and power up the inverter. The digital controller should immediately come to life with display and indicator lights. Test inverter output by disconnecting from shore power and generator - you should now have clean 120VAC output.
If replacing both the external DC disconnect fuse and internal 30-amp DC fuses doesn't restore your VFX2812M to operation, you're likely dealing with internal component failure that requires professional repair or replacement. Outback inverters have complex internal circuits that can fail and aren't user-serviceable. Don't attempt to probe deeper into the inverter's internal components or circuit boards.
Also be aware that repeatedly blown fuses indicate an underlying problem - don't just keep replacing fuses without determining the root cause. Issues like shorted DC wiring, failed internal components, or battery bank problems can cause fuses to blow repeatedly. If fuses continue blowing after replacement, contact an Outback-certified service center or qualified RV electrical technician. The VFX2812M typically costs $800-1200 to replace if internal repairs aren't economical.
Help us improve this article by flagging technical issues or inaccuracies.
Was this guide helpful?
Try our free RV calculators and tools to help diagnose and plan your repairs.
Browse RV ToolsWeight calculator, electrical planner, propane estimator & more