Nightmare repair on a 4206 XR

[Lemur]

A fellow local group member asked me to resolder the footpad sensor connector in the controller, he brought in the controller only, already taken apart, I replaced the footpad connector as it was too badly damaged and reflowed the hall connector.

A week later he had a code 16 and again asked me to repair his board, this time he brought in the complete board. The poblem was broken wire in the harness.
After reassembling the board, now a code 3 (over voltage) code came up, I had to open up the contrller and he had used thick silicone insted of flowable silicone.

It took an hour just to open the controller up and clean up the mess. It looked like he had damaged the 80v cap and the inductor during his assembly, but replacement of those parts did not cure the code 3. I now had to go into the battery box, no thick silicone on this, I used my test bms and the code 3 was gone, so the problem in in his bms, after consulting a bms repair expert, he advised to check the small capacitors to the left of the Max chip as they get knocked loose, however they looked fine, but the caps were coated with a real thick coat of conformal.
I used a toothpick and poked around the caps to remove the conformal and two caps came off with the conformal. I resoldered those back on and the code 3 was gone.
I rode the board for a few days and all seemed to be fine, but that is not to be, yesterday, I tried to test ride it again and a code 16 came up. I opened up the controller box again and test contiuity on the bms data wires and all was fine.
Then I used my test harness and the code 16 was still there.
I then used my test bms and the code 16 was gone, so the problem is in the original bms. I checked the bms write up and looks like the Vp1786 transceiver chip may be the problem, I had a few of those chips so no harm replaceing it, after scaping away the thick conformal, the chip pretty well fell off, two legs came unsoldered, replacement was straight forward but had be be careful not to lift the solder pads. No more cde 16 after that chip replacement.

I went for a long ride and turned the board on and off many times with no trouble codes.
Those early 4206 bms's were rumored to be troublesome, also if you need to replace the controller lid seals. I used thin double sided tape, but run your fingers over the part of the tape that you dont want to stick to the plasic case.

[Lia]

@lemur Amazing work, so much went into this and it's so cool to see it back running again!