John Graham-Cumming has a couple of fancy Dyson fans that do cooling (or at least blowing air around) and heating. They use a little IR remote control that attaches to the top with magnets. One of the remotes decided to stop working; its failure mode was: consume an entire CR2032 battery in a few days. Apparently, others also experience this problem.

Using a multimeter I discovered that the resistance across the battery terminals was 2.5kΩ when I was expecting it to be very, very high or even infinite.

But why was there 2.5kΩ across the battery? The culprit is the capacitor C1 which is in parallel with the CR2032. It’s decided that it would prefer to be a resistor! Sometimes capacitors fail like this.

I didn’t have a spare surface mount capacitor around so I simply removed C1. With C1 removed there’s no current drain when idle and the remote works fine. Unfortunately, Dyson didn’t design the remote to be opened and so the case didn’t survive.

Check out the complete diagnostic in the post here.