Introduction: The Backbone of Your RV's 12V Power System

Your RV's electrical ecosystem is built around a silent workhorse: the power converter. If you own a modern travel trailer, fifth wheel, or motorhome, there is an incredibly high probability that your rig relies on either a standalone wf 9855 converter or an integrated wf 8955 converter power center. These 55-amp power systems are responsible for taking 120V AC shore power or generator electricity and converting it into clean 12V DC power to run your lights, slide-outs, water pump, and refrigerator, while simultaneously charging your house batteries.

However, as RV technology evolves—especially with the widespread transition to Lithium Iron Phosphate (LiFePO4) batteries—many owners find themselves struggling with outdated charging profiles, dead units, or finicky "Auto-Detect" features. Whether you are troubleshooting a failing wf 8955an power converter, trying to figure out if your 8955pec converter can handle a new lithium battery bank, or planning a complete replacement, this guide provides the expert-level technical knowledge, step-by-step instructions, and hard-to-find hacks you need to keep your RV's power system running flawlessly.

1. Decoding the WFCO 55-Amp Family: WF-9855 vs. WF-8955 Series

To effectively upgrade or troubleshoot your power system, you must first understand exactly which unit is installed in your RV. While both supply 55 Amps of DC current, their physical form factors, installation locations, and wiring are fundamentally different.

Standalone Deck-Mount: The WF-9855 Converter

The wf 9855 converter is a "deck-mount" converter/charger. It is a standalone metal box that is physically separate from your RV's main breaker and fuse distribution panel.

• Location: Typically tucked away in a pass-through storage compartment, under a cabinet, or behind an access panel near your battery bank.
• Connections: It features a standard 15-Amp 120V AC power cord that plugs into an outlet, and two heavy-gauge DC output terminals (positive and negative) that connect directly to your 12V bus bars or battery.
• Purpose: It is used in larger RVs or setups where the electrical distribution panel is located far away from the batteries, allowing the converter to be mounted closer to the batteries to reduce voltage drop.

All-in-One Power Centers: The WF-8955 Series

The wf 8955 converter series refers to an integrated "power center" or distribution panel. This is the plastic-faced box you see inside your RV's living area containing your AC circuit breakers and 12V DC fuses.

• WF-8955AN: This is the older generation 55-Amp power center, featuring a classic brown or textured plastic front door. It contains the AC breakers on the left, DC fuses on the right, and the lower main board converter section at the bottom.
• WF-8955PEC: The wf 8955pec converter is the updated, modern iteration of the 8900 series. It features a sleeker, decorative door and bezel designed to blend in with modern RV interiors, but uses the same internal electrical logic and 55-Amp output capacity.
• The Main Board Assembly (MBA): Inside both the AN and PEC models, the actual "converter" is a slide-out lower section known as the Main Board Assembly (such as the WF-8955-MBA). This modular design means that if your converter fails, or if you want to upgrade its charging technology, you do not have to replace the entire distribution panel—you only need to replace the lower MBA.

2. The Lithium Upgrade Challenge: Why Your Old Converter Falls Short

One of the most common reasons RVers search for a wf 9855 converter or a wf 8955pec converter is because they are upgrading their house batteries from traditional lead-acid (flooded or AGM) to Lithium Iron Phosphate (LiFePO4).

If you hook up a brand-new LiFePO4 battery to an older, standard WFCO converter, you will run into several significant problems. This is because lead-acid and lithium batteries require completely different charging profiles to operate safely and reach full capacity.

The Three-Stage Lead-Acid Profile

Standard legacy WFCO converters utilize a three-stage automatic charging process designed for flooded lead-acid and AGM batteries:

1. Bulk Mode (14.4 VDC): Designed to fast-charge a significantly discharged battery. It runs at a high voltage for a maximum of 4 hours to push current into the battery.
2. Absorption Mode (13.6 VDC): The standard nominal operating mode. It slow-charges the battery and powers your RV's 12V appliances.
3. Float Mode (13.2 VDC): A low-voltage trickle charge designed to maintain the battery during periods of storage without boiling the electrolyte.

The Lithium Dilemma

Lithium (LiFePO4) chemistry behaves very differently. A lithium battery operates at a higher resting voltage than lead-acid (typically 13.2V to 13.3V when fully rested). To charge a lithium battery to 100% capacity and, crucially, to trigger its internal Battery Management System (BMS) to balance the individual cells, the battery must receive a constant voltage of 14.4V to 14.6V.

If you use an older standard wf 8955 converter (non-AD, non-Li):

• Under-charging: The converter will quickly drop from its 14.4V bulk mode down to its 13.6V absorption mode because it misinterprets the high resting voltage of the lithium battery as being "nearly full."
• Stuck at 70-80%: Because 13.6V is below the voltage required to fully charge LiFePO4, your expensive lithium batteries will never charge beyond roughly 70% to 80% of their actual capacity.
• No Cell Balancing: The cell-balancing circuitry in most LiFePO4 battery BMSs only activates when the charging voltage crosses 14.2V to 14.4V. Over time, unbalanced cells will drift, reducing the overall lifespan and performance of your battery pack.

3. Upgrading to Lithium: Step-by-Step Replacement Options

To unlock the full potential of your lithium battery upgrade, you need to swap out your legacy converter for a model that provides a dedicated lithium charging profile. Fortunately, you have several excellent options depending on whether you have a deck-mount or a power-center configuration.

Option A: The WFCO Auto-Detect (AD) Series

WFCO's flagship solution is their Auto-Detect line, which includes the WF-9855-AD (deck-mount) and the WF-8955-AD (or the replacement main board assembly WF-8955-AD-MBA for your existing 8955pec converter).

• How it works: These units use a microprocessor to analyze the charging behavior of your battery. It automatically detects whether you have lead-acid or lithium batteries connected and adjusts its charging profile accordingly.
• Lithium Profile: When it detects lithium, it switches to a two-stage profile, outputting a constant 14.4V to 14.6V to charge the batteries to 100%, then dropping to a 13.6V maintenance float.
• Pros: Clean, drop-in replacement; no switches to manually flip.

Option B: The WF-9855LiS (Remote Switch Series)

For those who prefer absolute manual control over their system, WFCO manufactures the WF-9855LiS.

• How it works: This deck-mount model bypasses the automated detection logic entirely. It features a physical connection port on the back. By placing a simple jumper wire across this port (or wiring a remote switch), you can force the converter to lock permanently into a dedicated Lithium profile.

Option C: Aftermarket Upgrades (Progressive Dynamics or Powermax)

Many seasoned RV electrical DIYers choose to bypass WFCO entirely and upgrade to aftermarket brands like Progressive Dynamics (e.g., the PD4655V) or Powermax Boondocker series.

• For WF-9855: You can swap it with a Progressive Dynamics PD9260 or a Powermax PM4-55.
• For WF-8955: You can buy a designated "lower section replacement kit" (such as the PD4655V) that replaces your WFCO main board assembly. These units often feature a physical switch or manual pendant that lets you choose between lead-acid and lithium modes with 100% certainty.

4. Troubleshooting the WFCO Auto-Detect "Green Light" Issue

While the theory behind WFCO’s Auto-Detect (AD) technology is excellent, in the real world, it is notoriously finicky. Go onto any RV forum, and you will find hundreds of frustrated owners complaining that their brand-new wf 9855 converter or wf 8955pec converter upgrade is stuck in "Lead-Acid" mode.

On these newer AD units, there are small status LEDs located on the circuit board:

• Green LED: The converter is running its standard Lead-Acid/AGM charge profile.
• Blue LED: The converter has successfully detected a Lithium battery and is running the high-voltage Lithium profile.

If your converter's light remains stubbornly green even though you have connected lithium batteries, you are charging at a slow 13.6V. Here is why this happens and how to fix it.

Why Auto-Detect Fails: The Voltage Drop Trap

The Auto-Detect microprocessor makes its decisions based on the current and voltage feedback it receives from the battery. However, most RV manufacturers install thin-gauge wiring (typically 8-gauge or even 10-gauge wire) over long distances (15 to 30 feet) between the converter and the front-mounted battery box.

When your lithium battery demands a high current, this thin wiring creates a significant voltage drop. The converter might be outputting 14.4V, but due to resistance, only 13.6V is reaching the battery. Conversely, the high resistance tricks the converter's microprocessor into thinking it is charging a lead-acid battery, preventing it from ever switching the LED from green to blue.

How to Force the Switch: Three Proven Hacks

Hack 1: The Heavy Discharge Method

To trigger the auto-detect logic, the converter needs to see a massive current draw that only a discharged lithium battery can pull.

1. Run your RV's 12V appliances (slideouts, jacks, lights, fans) with shore power disconnected until your lithium batteries are drained down to roughly 10% to 20% capacity (usually around 11.5V to 11.8V).
2. Plug your RV back into shore power.
3. The sudden, high-amperage bulk charge demand will force the Auto-Detect microprocessor to recognize the fast energy absorption curve of lithium, triggering the blue light.

Hack 2: The "Fool the System" Battery Disconnect Trick

If you don't want to deeply drain your batteries, you can trick the logic by removing battery resistance from the startup cycle.

1. Turn off the AC breaker to your converter.
2. Disconnect your house battery completely (either by turning off your master battery disconnect switch or removing the negative terminal cable).
3. Turn the converter's AC breaker back on. With no battery connected, the converter registers a completely open line.
4. Wait 10 seconds, then reconnect your battery. The sudden rush of voltage often shocks the microprocessor into immediately switching to lithium mode (blue light).

Hack 3: The Hardwired Jumper Solution (The Ultimate Edge)

If you have a newer revision of the WF-8955-AD or WF-9855-AD board, there are physical header pins on the circuit board that the factory uses for testing and programming.

1. If you contact WFCO tech support and explain your auto-detect is failing due to factory line resistance, they will often mail you a small physical jumper block.
2. Placing this jumper block across the designated pins (or soldering a 1k-ohm resistor between the test jumpers as detailed by advanced RV techs) bypasses the auto-detect algorithm completely, forcing the converter to stay locked in Lithium mode permanently. The LED will immediately turn blue and stay blue.

5. Step-by-Step Guide: Replacing a WF-8955PEC Lower Converter Section

If your current converter is dead (no 12V output when plugged into shore power), or if you are ready to swap your old board for a lithium-ready WF-8955-AD-MBA assembly, you do not need to pay an RV technician hundreds of dollars. This is a highly manageable DIY project that takes about 45 to 60 minutes.

Tools and Parts Required:

• Replacement Main Board Assembly (e.g., WF-8955-AD-MBA)
• Phillips head screwdriver
• Flathead screwdriver (or slot driver)
• Wire cutters/strippers (if splicing is needed, though most are slide-in terminals)
• Multimeter (to verify voltage)
• Electrical tape

Safety First!

Before touching anything inside your distribution panel, you must de-energize the entire system. Failure to do so can result in severe electrical shock.

1. Unplug the RV's shore power cord from the pedestal.
2. Turn off your generator (if running).
3. Disconnect your RV house batteries (remove the negative cables).
4. Use your multimeter to verify there is 0V AC on the main breakers and 0V DC on the fuse board.

Step 1: Open the Panel Cover

Press the latch at the top of your wf 8955pec converter door to open it. Remove the screws securing the plastic outer faceplate/bezel and set it aside. You will now see the metal breaker enclosure on the left, the DC fuse board on the right, and the lower converter compartment at the bottom.

Step 2: Disconnect the AC Wiring

Locate the three AC wires coming from the lower converter assembly:

• Black (Hot): Wired to a 15-Amp breaker (often shared with another circuit). Loosen the breaker screw and pull the black wire out.
• White (Neutral): Wired to the neutral bus bar. Loosen the screw and remove it.
• Green (Ground): Wired to the ground bus bar. Loosen the screw and remove it.

Step 3: Disconnect the DC Wiring

Locate the thick DC output wires coming from the back of the converter board:

• Red or Blue (Positive): This runs up to the back of the 12V DC fuse board. Loosen the lug screw on the fuse board and pull the wire free.
• White (Negative): This runs to the negative DC ground bar. Loosen the terminal screw and pull the wire free.

Step 4: Slide Out the Old Converter

There are typically two mounting screws holding the metal converter tray to the bottom of the plastic outer housing. Remove these screws. Gently pull the old lower board assembly straight out of the housing, guiding the disconnected wires through the plastic rear cutouts.

Step 5: Install the New Main Board Assembly

Slide your new WF-8955-AD-MBA unit into the bottom compartment. Route the AC and DC wires through the same access slots to the upper compartment where your breakers and fuses live. Secure the tray with the two mounting screws.

Step 6: Reconnect All Wiring

1. DC Connections: Insert the thick Red (Positive) wire into the positive terminal on the back of the fuse board and tighten. Insert the thick White (Negative) wire into the negative ground bar and tighten. Ensure you torque these screws firmly (20 to 40 in-lbs is standard; do not over-torque or strip them).
2. AC Connections: Connect the Green wire to the ground bus bar. Connect the White wire to the neutral bus bar. Insert the Black wire into the 15-Amp breaker and tighten the screw.

Step 7: Reassemble and Test

Double-check all connections to ensure no copper is exposed and all terminal screws are tight. Reinstall the plastic front bezel and secure it with its screws.

1. Reconnect your RV house batteries.
2. Plug the RV back into shore power.
3. Turn on the main AC breaker and the converter's 15A breaker.
4. Use your multimeter to test the voltage at your battery terminals. If the unit has detected your lithium battery, you should see a healthy charge voltage between 14.4V and 14.6V.

6. Frequently Asked Questions (FAQ)

Can I run my RV's 12V appliances without a battery connected to my WF-9855?

Yes. Both the standalone wf 9855 converter and the integrated wf 8955 converter are designed to act as a constant voltage power supply. They can supply up to 55 Amps of clean, regulated 12V DC power to your entire RV even if no battery is physically installed in the rig. However, you will need a battery if you plan to operate heavy, high-surge hydraulic slide-outs or leveling jacks.

What should I do if my WF-9855 converter fan runs constantly?

The cooling fan on these units is temperature-controlled and load-controlled. If the fan is running constantly, it usually indicates:

1. High ambient temperature: The compartment where the converter is mounted lacks adequate ventilation.
2. Heavy electrical load: You are running multiple high-draw 12V appliances simultaneously.
3. Failing Battery: A failing lead-acid battery with a shorted cell will continuously pull maximum current from the converter, forcing the fan to run indefinitely. Test your battery's health if the fan refuses to turn off.

What fuses protect the WF-9855 converter from damage?

Both the WF-9855 and the WF-8955 are protected by Reverse Polarity Fuses. These are standard automotive ATC-style fuses (usually two 35-Amp fuses for a 55-Amp converter) located on the rear of the deck-mount chassis or directly on the DC fuse board of the power center. If you accidentally cross your positive and negative cables when installing a new battery, even for a split second, these fuses will immediately blow to protect the converter's internal circuitry. If your converter has no output, always check these fuses first.

Can I upgrade my WF-8955AN with a WF-8955-AD-MBA?

Yes. The upgraded Auto-Detect Main Board Assembly (WF-8955-AD-MBA) is fully backward-compatible. It is designed to slide directly into the lower housing of both the older plastic wf 8955an power converter and the newer decorative wf 8955pec converter power centers.

Why is my converter only outputting 13.6V when charging my lithium battery?

This means your converter is operating in lead-acid "Absorption" mode. If you have an older legacy converter, this is its maximum output and it cannot charge your lithium battery fully. If you have a newer Auto-Detect (AD) model, the system has failed to recognize your lithium chemistry due to voltage drop across the factory wiring. Use the troubleshooting hacks outlined in Section 4 to force the unit into its 14.4V lithium charging mode.

Conclusion: Powering Your Adventures with Confidence

Understanding how your wf 9855 converter or wf 8955 converter functions is crucial to maintaining a reliable, worry-free RV experience. Whether you choose to stick with the simplicity of an integrated wf 8955pec converter, upgrade to an Auto-Detect model, or completely bypass automated logic with a manual switchable unit, having a solid grasp of your 12V charging system prevents dead batteries and expensive repair bills. By choosing the right upgrade path and knowing how to bypass finicky sensors, you ensure your electrical system is always ready for the open road.