After some advice. So this is the telecommunications box from my car which is sat right under the aerial. This aerial is known for leaking water inside the car and potentially inside the box. I took it out and opened it and found some light rust on the top of a couple of components which looks to have been there for a while.
However near the connectors (not near the area that could have been compromised by water) one of the connectors has burnt out including the track it’s attached to. Even the casing is burnt. But seems to be contained to that one pin which I have determined as the 12v+ from the main car computer
I want to know your thoughts on if you think this damage could have come from the ingress of water? Or maybe overloading the 12v+? Or anything else.
I know there is since of water ingress from the rush on other components (well away from the terminals) but the unit itself is bone dry so struggling to believe it is because of that. Any thoughts welcomed. Thanks.
I wonder whether the circled black component (Tantalum cap? Diode?) is shorted?
The adjacent route to the ground plane also appears to have been burned away.
The board seems to have a few things like that on it. I’ll attach a picture of the whole board. There was nothing inside the housing that fell out. Could it be something on the reverse of the PCB? I am unable to get it out of the housing without breaking the housing so will be a last resort
Don’t see any signs of water on the board. If there had been water you would see a bit of residue left when the water evaporated. The antenna connection and power connections are normally water proof, so automobile electronics are pretty resistant to water. You are seeing normal component failures! Did the box still work?
It was, until it went in for an oil service which shouldn't have damaged it, but they did disconnect the main battery to do it. Then they washed it and when I collected this unit was dead.
They want around £1500 for this little box and then recoding a new one to the car so would be nice to see if it can be fixed.
There is continuity around the board if ground (to the ground plug terminal) including to the battery backup compartment on the board.
I didn't see any water residue on it when I opened it. Apparently it is a known problem that the antenna leaks and floods the board but it really doesn’t look water damaged.
So they returned it to you in this state and now they want £1500 to fix it?
its difficult to tell, but that looks like impact damage?
On your high res version It looks like there is a crack that tracks back to where the fixing bolt is.
Given the proximity to the antenna connector and the voltages marked on the silkscreen, it would seem that this is 3.3V and 5V circuitry. That something happened at the power supply end of the board is evident from the first image. One might speculate that this same event might have also caused a cascade of failures further down the line in the lower voltage parts of the board (i.e. these parts of the board also got 12V).
Of course this is only speculation and IMHO.
Do those connectors in the first image have polarity keys (notches or tabs) to prevent the plugs from being inserted the wrong way around or into each other?
So it's a BMW. The oil service should have been £170 but they called me half way through and said the oil filter tore as they removed it and in case some of the paper went into the engine they need to change the whole housing which costs over £1500!! Thankfully BMW picked up the tab as it’s a known issue and was on a worldwide service bulletin in 2020.
So they fixed that and then when I went to collect I had an SOS error on the dash. They said that the oil filter change had nothing to do with it as they don’t go near that part and might be a coincidence. Unless it rained heavier than it ever has INSIDE their workshop I'm not sure how water could have leaked inside the unit to fry it like what they think the issue is. But of course not their fault.
This is also like a ££££ job so absolutely doing my head in.
I tried changing the battery backup in it as that can also fail and cause the same issues so bought a new battery (8v) put it in but nothing. That’s when I took the lid off and found these problems. There is continuity between negative on the terminal, battery negative terminal and certain components on the board, but obvs no continuity for the positive after that fried piece of track.
the connectors can only go in one way so cannot have been plugged in reverse.
Similarly the unit hasn’t been touched since fitting as it’s right under the rear headlining so blunt trauma on the PCB is unlikely, unless it was from before fitting.
