Wfco8900 not providing 12 volt power

Ghannan
Ghannan Member Posts: 45
edited October 7 in Battery/Electrical & Solar

My 2023 tab400 has avWFCO8900 converter. With battery switch off, no 12 volt equipment turns on, and the battery does not get charged. With battery switch off, the lugs that the red and white wires that come from the converter box at the bottom of the WFCO unit reads zero volts. These lugs are at the top left of the 12 volt fuse panel. Of course, with battery switch "on", those lugs read 13 volts. Is my 130ac to 12v dc converter dead? All connections are tight. TIA

Comments

  • Grumpy_G
    Grumpy_G Member Posts: 784

    Is there 120V at all in the trailer ? Outlets, AC working ? Otherwise switch the breakers off and on to make sure they are not tripped.

  • Ghannan
    Ghannan Member Posts: 45

    Oh, yes, all 120v is working. 12 volt coming only from battery, not the Wfco.

  • Ghannan
    Ghannan Member Posts: 45

    Fuses and breakers all OK.

  • qhumberd
    qhumberd Administrator, Moderator Posts: 899
    https://tab-rv.vanillacommunity.com/discussion/comment/223357#Comment_223357

    No expert here but just curious about the 12V systems. I was not aware the WFCO needed to convert anything when disconnected from shore power. I thought the battery voltage would just pass thru the WFCO and power each fused 12 circuit when the battery is on. So how does that work?

    2019 T@B 400 Boondock Lite towed by 2016 5.7L Toyota Tundra

  • Ghannan
    Ghannan Member Posts: 45

    Yes, that is true. We are getting 12 volt power from the battery. When I turn the battery switch off, the Wfco should provide 12 v power to everything, but it is not powering any 12 v circuit right now. It looks like the Wfco converter might be dead. I think there are lots of complaints about the reliability of the Wfco converter on this forum

  • Ghannan
    Ghannan Member Posts: 45

    There are wires coming from shore power to the 120 volt circuit breaker panel (feeding 120 volt circuits and the 120 to 12 v converter, 2 wires connecting the 12v output from the converter to the 12volt fuse panel (supplying all 12 volt circuits including charging the lithium battery) and another 2 wires from the battery connecting to the same 12 volt fuse/distribution panel as the converter output is powering.

  • qhumberd
    qhumberd Administrator, Moderator Posts: 899
    edited October 7
    https://tab-rv.vanillacommunity.com/discussion/comment/223364#Comment_223364

    OK I understand now. I have messed with mine during my lithium battery upgrade and so I am a little familiar. This test sequence seems reasonable but we have a lot of very experienced members who can critique and assist as well. The reverse polarity fuses are a bit hidden and are worth a look too.

    Step-by-Step Diagnostic Checklist

    Before ordering a replacement converter section, verify these three potential points of failure:

    1. Confirm 120V AC Power Is Reaching the Converter

    Test Shore Power: Plug a lamp or hairdryer into an interior 120V outlet to ensure shore power is live inside the camper.

    Reset the Converter Breaker: Locate the 120V breaker panel on the WFCO. Find the breaker labeled CONV or CONVERTER, flip it firmly to OFF, and then back ON.

    2. Check the Reverse Polarity Fuses

    WFCO panels have two (sometimes three) 30-amp (green) or 40-amp (orange) reverse polarity fuses on the 12V fuse board, usually set off to the side or positioned vertically.

    If these fuses blow (often caused by a temporary short or backwards battery hookup), they isolate the converter output from the distribution board.

    Pull both fuses out and test them for continuity with your multimeter.

    3. Measure AC Input Directly at the Converter Deck

    Turn off shore power, remove the lower WFCO cover, and locate the 120V input wires powering the converter section (the bottom deck unit).

    Re-engage shore power and carefully measure the AC voltage where the black wire connects to the converter breaker and the white wire connects to the neutral bus bar. It should read ~120V AC.

    Verdict

    If you have 120V AC entering the converter, the CONV breaker is ON, and the reverse polarity fuses are intact, then the converter's internal circuit board (Main Board Assembly) has failed.

    Replacement options:

    Direct Swap: WFCO Main Board Assembly (MBA) replacement deck corresponding to your WF-8900 series model (e.g., WF-8955-MBA or WF-8955-AD-MBA with Auto-Detect for Lithium).

    Upgrade: Progressive Dynamics PD4000 series converter replacement section (e.g., PD4045MBA), which is widely favored in the T@B community for its reliable multi-stage charging algorithms.

    2019 T@B 400 Boondock Lite towed by 2016 5.7L Toyota Tundra

  • MuttonChops
    MuttonChops Member Posts: 2,072

    @Ghannan If I'm reading your posts accurately it indeed sounds like the WFCO Converter has failed. While not a common failure it is frequent enough that Amazon (and others) sell replacement converter assemblies.

    These figures might help you visualize the wiring (note: no solar to battery shown)

    BadConvertorChart.jpg

    '18 320 S, pitched axle, 3020HE; PNW based

    TV: '17 Colorado V6 Z71 4x4, Tow Package, GM Brake Controller
    TV: '25 Canyon AT4
    Adventures: 50 Nights: 415 Towing Miles 50,650

  • Ghannan
    Ghannan Member Posts: 45

    Is the PD4045 unit the popular replacement for the WFCO 8955? Installs without modification?

  • Ghannan
    Ghannan Member Posts: 45

    Meanwhile, I put a 10 amp battery charger on the battery, with negative cable on the downstream side of the Victeon shunt. Now reading 100% state of charge

  • GregR
    GregR Member Posts: 17

    My 2022 400 had a similar issue with its' WFCO 8955 a couple years ago and I ended up replacing the Main Board Assembly (MBA).

    There is a "Troubleshooting Flow Chart" in the "WF-8900-AD SERIES" Operator's Manual that should be available at wfcoelectronics.com. My copy of the manual is the older version (orange and blue in color) and WFCO revised the manual in 7/24 (blue and white in color). My copy includes a page on "Replacing The Converter Section (MBA)" while the newer manual does not include that page.

    If you can't find the manual(s) online, private message me with your email address and i will send you both manuals.

    2022 T@B 400 BD, 2018 Toyota Tundra, Palisade, CO
  • Binghi
    Binghi Member Posts: 416

    My WFCO 8955 PEC failed and I had a Progressive Dynamics PD4655V converter installed as a replacement. I believe it slides into the WFCO converter housing with only a slight modification. The PD converter has worked flawlessly. I had the installer increase the gauge of the wire between the converter and the battery, and the PD charges the battery in a jiffy.

    2021 400 BD / 2023 Ford F150 / Austin, TX

  • Ghannan
    Ghannan Member Posts: 45

    Go figure ... Last night at about midnight, the 120 outlets in the bedside cubby and the TV lost power. This morning, I found that the circuit breaker for the converter and those two outlets (all on the same breaker) had tripped. I had previously tripped all breakers off then on. I tripped then on the converter breaker on, and the converter powered on and it's fan started, as normal. 9 amps flowing into the battery, which had dropped to 77% overnight, as expected. Mysterious, but I will take it. At least I now have a backup battery charger to add to the trailer supplies. Thanks for everyone's help, as always.

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