Toby Wint_rmuteMar 23

I'm struggling to fix an electronic circuitboard -- can anyone offer suggestions?
It's a circuitboard from a motorcycle instrument panel, manufactured in 2019. It has a layer on each side. I don't know if it has any internal layers.
There are two push switches, and the controller seems to think one of the switches is continually pressed.
Testing the switch with a multimeter, it looks fine. It's normally open, and when pressed, closes the circuit with very low resistance. This is identical to the other, working, button.
The circuitboard has some test points, including for GND and the switches.
When my multimeter is connected to GND and the test point for the bad switch, the results appear good.
ie. No connection normally, and then a very low resistance connection when pressed.

I'm trying to work out what else could be the problem. Maybe the connection to the microcontroller has shorted out against a neighbouring connection?
I can't visually see anything like that, but I don't have a circuit diagram and the circuitboard has a layer on top of it obscuring the tracks.

Maybe a track has somehow broken inside the circuitboard and shorted to ground? I can't see any visual damage, and I guess I wouldn't know how to fix this even if there was.

Are there other possibilities I'm missing?

Show threadzl2tod

@wintrmute

What is the switch meant to do?

It sounds like the circuit board and the switch are OK.

Try measuring voltage on the switched line to make sure the switch is changing the voltage all the way up or down. Water damage could be creating leakage stopping the voltage from falling away.

If it's turning something on and off via the microcontroller the output switching device could be unwell, or either the input or output parts of the microcontroller could be stuffed.

Mar 23 at 5:53amWeb
Show threadToby Wint_rmuteMar 23

@zl2tod Motorcycle UX designers are awful, so these two switches do many things, depending on whether you press one, or hold one, or press one while holding the other, or hold both at once.

Because of how the unit behaves, I'm pretty sure the error is on the input side of the controller, not the output.

Show threadzl2todMar 23

@wintrmute

Have you had the switch apart or tried another switch?

Show threadToby Wint_rmuteMar 23
@zl2tod the switch is maybe 4x4 or 5x5mm and is soldered directly to the board. I don't think it really comes apart.
Show threadToby Wint_rmuteMar 23
@zl2tod That's a good idea re voltages when running. Unfortunately I don't really have a good test rig to check voltages when running on the bench, and it's too awkward to get at test points when it's assembled on the bike. Maybe I can get hold of a compatible plug for the all-in-one socket so I can power it on the bench though? (The instrument panel has ~20 wires on its single plug)