Glad to hear you are back up and running.
As I’ve suffered 2 failures myself, and also I’m an electronic engineer, I wondered 3 things:
A) why the water gets in (if it does)?
B) is repair possible?
C) when the supply of used units will begin run out?
Answering these in a random order hopefully without rambling on excessively:
The answer to (C) will of course be when the rate of A2s getting broken up for parts begins to exceed the rate of failures of the module of cars still in the road. Since the module is an A2-specific part (8Z0 prefix part number), presumably no other models fan controller module can be used, though it would’ve interesting to know other views on this.
As to (A), I disassembled both failed units.
To do this, lift the ends of the label showing the connectors and remove the 4 Torx screws from the plate underneath. This allows the plate to be levered out, destroying the mastic seal. Then, underneath is a spring steel clamp which clamps 3 transistors to casting rib as a heatsink to cool them. There is a thermal pad for electrical insulation (but thermal conduction) between the transistor tabs and the casting rib. The clamp can be levered up This then allows the plastic clips around the top to be peeled up gently a few at a time, wedging with toothpicks or similar until the whole connector/PCB can be slid out.
The mastic plate seal is pretty good, I didn’t see this as a route in for water. I think the only other routes in are:
1) Seal failure around the wires
2) Seal failure between the on-wire connector housing and the plastic part of the case.
3) Breakage of connector latches, resulting in no seal compression.
4) Seal failure between the plastic and metal parts of the case.
5) Porous casting.
6) Effect of pressure washing engine???
Both of my failed units had clear signs of water in the bottom of the case casting, with corrosion to the PCB traces and surface mount resistors and ceramic capacitors. I couldn’t see any issues with the connectors or seals in either module of mine, so it is still a mystery.
As to question (B), although I could have attempted repair, I decided to get a used one in both cases because of reasonable cost currently, and also the risk of overheating due to no fan operation leading to other much more expensive problems like a blown heat gasket if my repair did not last.
@RZX I’m not sure if you’re interested in disassembling your failed module, (no worries if not), but if you are able to get it apart it would be good to know if it had also suffered water ingress.
All the best,
Matt
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