Sunday, March 10, 2013

Old dog learns a new trick (or Why men don't read instructions)

You would think that changing a bulb would be easy. After all I recently bought a couple of daylight bulbs, and installed one of them in seconds. The lounge is much brighter and the power consumption only a quarter of the previous incandescent bulb. So when Jo said the offside headlight had stopped working I was expecting few minutes work. How hard can it be? First find the book. OK, I lie! First open the bonnet and look at the connection, try to take it apart, and fail miserably.
There are three lights in the set, a side light, a dipped light, and a full beam light, each with its own enclosure. They are not visible, or at least not properly visible. I put the lights on to check that I was trying to disconnect the correct one - I was. The book says that disassembly is a three stage process.
  • Unclip the power supply by depressing the plastic clip and separating the connection. 
  • Turn the cover counter-clockwise and remove the cover.
  • Remove the connection to the bulb, if it is stiff wiggle it.
  • Unclip the bulb clip and remove the bulb.
(Count the steps carefully did you get three?) This process failed at the cover removal, until I realised that counter-clockwise meant clockwise the picture was from the back of the unit, I was working from the front. Once it was all removed I connected the circuit and the bulb lit. So I put it all back together properly, and the bulb failed to light.
Having no idea what the problem was, and having been working on it for an hour, I decided to go to Halfords to get a spare bulb. This served as a very good reminder of why I don't go shopping on a Saturdays. Queueing to get into the car park, and out of it is a big disincentive especially in March.
Once again I made a fatal error and looked in the book. I need a 472, but the 472s have three prongs and two filaments, the bulb I want has two prongs and one filament. I stood there pondering, and an assistant asked if she could help. I told her what I was looking for. "You need a 477." She found one and gave it to me, it was indeed what I was looking for.
Back at home I fitted it in 20 minutes and it worked. I had learnt just where to apply pressure, when and how far to turn the cover, the alignment of the prongs and a host of other things without ever seeing inside the bulb housing at all. I will probably remember 477 long after they've changed all the numbers too. I have also learn something about interpreting manuscripts, sometimes you can make sense of them sometimes you can't.

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