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I have an electric bike, which started to act strange a while back. The switches no longer function properly, possibly because things got moist. During the winter the cover of the bike was shredded by a storm, and it took a while for me to get a new one.

Now I've opened up the switch. Its a really simple board with just 5 switches on it.

These are the buttons enter image description here And this is underneath them. enter image description here

When I flip the board over I see this white stuff that resembles fungal growth to me. (Sorry for my background in agriculture I guess).

enter image description here

Now I know the board shorts as it acts continuously like the plus and minus button are pressed together, while none are actually pressed. The other 3 buttons function properly.

Now I highly doubt the white stuff to be a fungus, as I don't think it would conduct very well. What would be a likely explanation for this, and how to restore the functionality of this board.

I've looked at simply replacing the part, but there are only parts available with the attached computer included. That would set me back about €200+, so I would love to get this fixed.

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  • \$\begingroup\$ First post here, so any suggestions for improvement are encouraged! \$\endgroup\$ – Luuklag Apr 5 at 14:25
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    \$\begingroup\$ Far more likely than fungus is that what we're seeing there is some corrosion caused by a little moisture. Superficially it doesn't look bad, so I'd suggest giving that area a scrub with an old toothbrush dipped in isopropyl alcohol. Be generous with the alcohol so that anything you scrub loose gets washed off the board. \$\endgroup\$ – brhans Apr 5 at 14:31
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    \$\begingroup\$ That's not fungal growth, it's corrosion of the solder joint and flux residue around it. You can try to clean it off with normal cleaners like isopropanol. \$\endgroup\$ – Hearth Apr 5 at 14:31
  • \$\begingroup\$ Isopropanol and a toothbrush is your friend to get rid of the white residue. Can you measure the resistance across the switches when they are pressed? Does a drop of electronic cleaning spray in each button make any difference? \$\endgroup\$ – winny Apr 5 at 14:50
  • \$\begingroup\$ @winny my father in law measured the switches, and they all appear to function properly, that is the resistance changes. \$\endgroup\$ – Luuklag Apr 5 at 15:12
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That's not fungal growth; it's corrosion of the solder joints and flux residue around them. You can clean it off with normal cleaners like isopropanol.

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  • \$\begingroup\$ Are there any common household items that could be used in replacement of isopropanol? For example acetone perhaps? This would save me a trip to the stores :) \$\endgroup\$ – Luuklag Apr 5 at 15:05
  • \$\begingroup\$ Acetone should work, but I'm surprised you have acetone and not isopropanol. You might know it as isopropyl alcohol or just cleaning alcohol? Ethanol would work as well. \$\endgroup\$ – Hearth Apr 5 at 15:08
  • \$\begingroup\$ Well nailpolish remover is simply acetone, which I happen to have around :). Using alcohol for cleaning here isn't that common. \$\endgroup\$ – Luuklag Apr 5 at 15:10
  • \$\begingroup\$ That's fair! I would be careful since acetone dissolves a lot of plastics, though. If you have any on hand, just using vodka would be a viable solution as well. \$\endgroup\$ – Hearth Apr 5 at 15:11
  • \$\begingroup\$ Thanks for the tips. I'll go scavange tonight to see what is around. If acetone dissolves the board I better not use it I guess. \$\endgroup\$ – Luuklag Apr 5 at 15:14
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It seems possible that water has got in and some form of electrolysis has taken place and the white deposit you see that is remaining is some kind of salt (an electrolyte present in most water) that, with the presence of some moisture, will still act as a reasonably good conductor of electricity.

how to restore the functionality of this board

There's half a chance that if you removed the "salt" (or deposit) that the problem will be fixed. Then I suggest you lacquer the board but don't get the lacquer on the switches in case it seeps in. However, the switches may already be damaged internally but, luckily, they are common or garden switches and can be easily replaced.

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  • \$\begingroup\$ Thanks for your elaborate answer Andy. I think your answer would improve if you included (a reference to) how to best clean the board and how and which lacquer to aply. \$\endgroup\$ – Luuklag Apr 5 at 15:08
  • \$\begingroup\$ @Luuklag haha that wasn't elaborate at all especially as I didn't give cleaning instructions LOL. It's just a guess. I mean, what else could it be? \$\endgroup\$ – Andy aka Apr 5 at 16:21

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