Thread: Cooked ECU

Originally Posted by djam1

That I do
I should be able to retire by selling them

I hope your not planning on retiring anytime in the next few decades...

Matt's ECU turned up in the mail today and I was a bit curious so see if I could find evidence of why it failed.

Matt says that the ECU was in it's current state when he bought the Deefer.

The first thing I noticed was that the ECU has been swimming at some point:


The back side shows that the water/mud had splashed over one (possibly two) of the six vent holes on the back of the ECU:



The inside of the base shows that mud, and most likely water had entered the ECU housing:



This isn't a great shot but you can see a white residue between the circuit board and case in a couple of places. The residue completely spans the gap in one place. I'm assuming these residues are salts and minerals left behind when water evaporated. You can also see a burnt patch just to the left of centre where an additional resistor has failed.



The blown underside resistor is connected to the hexfet transistor with the purple paint dot. You might be able to make out the while residue on the circuit board connecting the three legs of the transistor. My guess is the residue may have provided a leakage path for current which has eventually caused the resistors to fail.



The worst damage is under the resistor/zero ohm link on the topside. The board is burnt and one pad has come loose from the surface, although there is still continuity with a nearby via.

I suspect the moral is that water and electronics don't play nicely. If you go swimming with your Td5 you need to take precautions to ensure the ECU isn't submerged. Sealing the vent holes on the back might be a good idea too.

cheers
Paul