Another busy weekend of MIEV repair here, after far too long a wait for parts. The tombstone form factor of the resistor is quite unusual, and I was unable to find a 33 ohm one anywhere, so I decided to go higher rather than lower and substituted a 47 ohm resistor. It, and a replacement relay arrived late last week, so this weekend I got into the repair itself.
I got myself a vacuum desoldering station, as I wanted to get the pair of boards completely apart and also was a little frightened of damaging the board with excessive heating. This proved to work fairly well - much easier than solder wick, or the clapped out station I had access to at work.
Removal of the relay and resistor was officially Hard Work. They were effectively stuck down underneath by the potting compound, as well as being soldered in on heavy tracks, and it took lots of applications of the desolderer to get the pins mostly clear. I used a fine scalpel to cut under the relay once I'd desoldered the pins, and that then let me lift it. Once removed, and after a bit of board and pad clean-up, fitting the new components and reassembling the module was fairly straightforward.
Plugged it back into the car, put things mostly back together, triple checked my wiring, crossed fingers and toes, and then applied mains.
The joy of hearing the charging process start was rapidly dissipated when I saw smoke rising from the charger - I cut the power hurriedly.
I then disassembled it all again. The resistor is once again open circuit, so lots of current must be being drawn right from power on. There is no sign of any other damage on the top board, but there's a smoking crack in the potted module underneath. The sad/annoying part of this story is that when I looked back on the photo I took of the module and mezzanine board from when I had it apart the first time the crack was already there - I'd overlooked it because I was too focussed on the resistor failure on the top board. Below is the original photo - the problem crack is in the middle of the four epoxy squares at the top left. The blackening is a little more obvious now.
So now it all gets a little more complicated - it looks like I'll be doing some epoxy mining. I'm wondering if it is worth trying to get an X-ray of the module first to try and get an idea of what's happening there.