RV Power Converter Replacement

Came home one day and heard the gas alarm screeching from inside the trailer.  2007 Funfinder X139 By Shadow Cruiser RV.
None of the 12V lights would come on. Checked the battery and found it nearly dead. (The alarm was screeching due to low voltage and not gas detection).
Even without a battery the 12VDC electrical should work.
Opened up the charge controller panel and found the 120V circuit breaker tripped.  Reset it but something on the charge controller went poof.

Not sure if the bad battery caused the charge controller failure or bad charge controller caused the battery to fail?  Battery was original 2007 so it had a good life (6 years).

The original charge controller / electrical panel is model WFCO 8945 (45 Amp 3 stage converter).

Looking at the Internet found that the replacement charge controller is really easy to find. To me that means there is high demand as they go out frequently.
I opted to upgrade to a bit better unit. Instead of WFCO, I went with a Power Max Boondocker.  Model PMPC-55-MBA (same as PM4B-55-MBA)

NOTE: The MBA designation is the 'open back' direct WFCO replacement shown here and is made to fit in the WFCO circuit panel enclosure. There are 3 MBA versions  45, 55, & 75 Amp.
Without the MBA means closed box surface mount versions shown here.

These are sold as 4 stage charge converters. The 1-3 stages are similar to other chargers. The 4th stage is the desulfation cycle. 

Key Features of the Power Max Boondocker Series

I got the new charge controller from here: Best Converter  They sell the original WFCO replacements as well.

This model was made to be a direct replacement for the WFCO unit. I chose the more powerful 55 Amp unit to replace my 45 Amp unit. (This is available in 45, 55, and 75 Amp).
If you choose to replace with the same model WFCO unit then you can still use these instructions as a guide.

The panel is made up of 3 compartments.

  1.  Breaker Panel (120 Volt AC)
  2.  Fuse Panel (12 Volt DC)
  3. Charge Controller (12 Volt DC)
The WFCO 8945 charge controller shown here

 Tools required

Remove old unit:
  1. Unplug AC power to the trailer and switch off all breakers. Turn off all light switches to minimize arcing at the battery terminals or fuse. 
  2. Disconnect the battery. (Remove main battery fuse which is in the battery cable near the battery OR if equipped turn the battery shutoff switch  OR disconnect cables from battery terminals)
  3. Open the access panel door and remove 1 screw from each side of the upper panel. 
  4. Tilt panel back slightly then pull the front panel up and out.
  5. Remove 2 screws from the base plate of the charge controller. Note screws are different than the other 2 panel screws. 
  6. Find the black wire from the charge controller and remove it form the breaker.
    Note that the black wire may be 'pigtailed' to another circuit. (Orange wire-nut in above photo). Remove the wire-nut to disconnect the other circuit if present.
  7. Remove the charge controllers white and green wires from the panel neutral and ground terminal blocks. 
  8. Dislodge the DC fuse panel board from the plastic clips.
  9. Find the white and red wires leading to the charge controller and remove them from the DC fuse panel.  Leave all other wires attached.
  10. Slide the old charge controller out of the bay and pull the wires through the holes and remove the charge controller. There is no need to remove the plastic baseplate from the bottom of the controller.

Install New Controller Unit:

  1. Route wires from the new controller through the holes and slide the new unit in place into the guide slots.
  2. Secure baseplate with 2 screws removed in step 5 above.

AC Connections:
  1. Connect the AC ground wire (green) wire to the ground bus. Note I had to move some of the other grounds to different locations as the green wire was a bit short to reach where the old one was. 
  2. Connect AC neutral wire (white) to the neutral bus.
  3. Connect the yellow crimp pin on the AC hot wire (black) to the breaker.
  4. Connect the other circuit with the included wire nut to the 'pigtail' as before. (If no 2nd circuit then just put the wire-nut over the single wire).
Note your breakers and wiring may be in different positions depending on how the circuits were installed at the factory.

DC Connections:
  1. Connect the DC (-) wire (white) to the terminal (-) terminal
  2. Connect the DC (+) wire (Blue) to the (+) terminal where the old red wire was.
  3. Snap the DC fuse panel back into place.

Final Assembly:
  1. Double check that all connections (set screws) are tight.
  2. Replace panel front cover with 2 screws.
  3. Connect battery & fuse

Completed install and wiring