"Lights!" said Fred
Battery powered bike lights are notoriously unreliable and the Nightriders we use are no exception. After yet another failure within minutes of leaving home, even though the batteries where freshly charged, I decided to get drastic.
The problem lies with the switch and contact design. The switch works by pushing a contact onto the back of a blob of solder on the back of the bulb. Unfortunately, solder oxidises and forms a high resistance film, which causes the light to go dim even when the batteries are OK. Vibration makes this worse, as it spreads a thin film of solder all over the switch blade.
To add to the problem, the contacts from the batteries are held to the case with small plastic mushrooms. After a while these come loose, making the switch operation even worse.
The solution is to fix the contacts properly, replace the switch with a proper one and hard wire the bulb to the switch. You will need four 2mm nuts and bolts, a miniature slide switch and a length of wire, plus a 2 mm drill, a pair of cutters and a soldering iron.
Drill right through the case at the lower mushrooms and put in the 2mm bolts. Secure with nuts, cut off the excess thread and bash the end to stop it coming undone.
Now bend the end of the switch contact though 90 degrees and cut it off as shown. Prise out the old switch toggle and discard.
Place the toggle switch in the switch hole and ensure that it can move fully, opening the hole if required. If the switch toggle protrudes too much, trim it down so that it is protected by the plastic moulding - this will reduce the risk of it getting accidentally switched on in your bag. Mark and drill the fixing holes for the switch and bolt it into place, again ensuring that the bolts can't shake loose.
Solder a short piece of wire from the left hand contact to the centre contacts on the switch. Now solder a wire from the lower contacts to the centre of the bulb. Carefully put the whole thing back together and it should work. If you find you have a gap at the side of the new switch fill it with Blutack to keep the wet out.
The ideal light would be one where you just plug it into a holder when you get home and it automatically recharges the batteries overnight. (Manufacturers, please take note!)