If you remove the computer from its handlebar mount, you will find two metal contacts (three for units with cadence function). When the magnet is not close to the 'sensor', the switch is open, so there is no connection between the two wires. When the magnet gets close enough, the switch closes, making contact between the two wires in the cable. What the manufacturers grandly call a 'sensor' is actually nothing but a magnetically-operated switch. First, you need to understand how these units work. The wiring is easy to check if you have an ohmmeter or a continuity checker (you should!). On the other hand, a front-mounted sensor doesn't do much for you when your bicycle is mounted on a trainer! Another area of potential difficulty with-rear mount units is that wiring under the chainstay can be damaged by mounting the bike in some trainers. The wire loop must also be kept safe from contact with the tire, which will wear it through in just a few miles. Rear-mount units require a bit more care, because you have to allow a loop of wire sufficient for the handlebar to be turned fully in both directions without overstressing the wire. Front-wheel reading also can be more accurate, because the front wheel does not 'creep' due to pedaling or skid when braking. The wire should go up the fork blade to the front brake, and follow the brake cable to the handlebars, without being attached to the frame at all. Front-wheel reading computers should be more reliable, because when they are properly installed there are no loose loops of wire. The usual problems occur around the headset, where the wire can be pulled too hard if the handlebar is turned farther than usual. Wiring ProblemsĮlectrical wiring on bicycles is often subjected to serious abuse, and it is very common to have breaks in the wiring, particularly if the wire is not properly routed and secured. A misaligned magnet can also result in odd or doubled readings - see the article on that topic. These are easy to align, but they also may rotate around a spoke, so the sensor does not respond. This trick is particularly useful when you have more than one set of wheels with different spoke patterns so you can't duplicate the magnet placement. I have sometimes used small button magnets from Radio Shack secured to the spokes with transparent tape. The magnet should preferably be mounted close to the hub, so it travels past the sensor at a low speed, giving the sensor more time to respond. Sometimes, substitution of a more powerful magnet can make the difference in getting a computer to work. The more powerful the magnet, the less fussy its alignment with the sensor.

Some magnets are more powerful than others. Also try sliding the sensor or magnet, one or the other, closer to the hub, or farther away. The sensor will not respond if too far from the magnet. Magnets and Magnet Alignment report this adīy and large, wheel magnets used in cyclecomputers are very ordinary, and may be interchanged from one brand to another. Some other units have a special procedure to 're-boot' the processor, usually by pushing all of the buttons at once. Genuine Cateye batteries, which are no longer available, came with a special little piece of thin plastic that can be inserted between the two batteries and then yanked out to establish contact cleanly. Many Cateye Solars have been discarded as defective, when they only need to have the batteries re-installed correctly. This is a particularly common problem with the Cateye Solar, which has very tight spring contacts and uses two small batteries that are a bit hard to install. The unit may show all 8's, or random fragments of characters, or may come up blank. This can cause 'garbage' readings to appear.

If the battery makes contact on a 'bouncy' way, the irregularities of contact as the battery is pushed in can send confusing messages to the circuit. Ideally, the battery should make instantaneous, solid contact with its terminals, but in some cases, this is not so easy to do. Some units are a bit fussy about how cleanly power is restored. When the battery is replaced, power is restored to the computer.

Cateye bike computer manual c137533