How come I often have to turn a long tube fluorescent bulb for it to turn on Sometimes just tapping the bulb will make it turn on Is the bulb bad or the socket or the ballast?

If the tube always stays lit without any trouble after it has been "started" by tapping or twisting it then the problem is not likely to be inside the tube itself but its contacts may need cleaning. If the tube flashes but never stays properly lit then it needs to be replaced. The problem may also be caused by corrosion on the contacts of the tube's "starter" - a small white or metal tube that will be found screwed into its own special socket somewhere on the light fixture. If that is the cause of the problem, tapping anywhere on the light fixture - including the tube - can often get the starter to work. Or maybe the starter itself needs to be replaced?

The first thing to check is the tube's starter. Starters don't last forever, they can only be expected to have a useful life about the same as a fluorescent tube. Switch off the power supply at the main panel, take out the starter tube by twisting it slightly anticlockwise and shake it. If anything sounds "loose" inside then the starter tube may be faulty. Anyway it's worth doing this bit of cleaning: using a small craft knife or penknife, scrape the starter's two contacts to make them shiny all over, including all round the thinner "posts" under the mushroom-shaped tops. Also, if you can see them, clean the contacts inside the starter's socket, but that may be difficult to do if they are hidden inside the socket. Replace the starter in its fixture, turn on the power and switch on the light.

If that made no difference then the first thing to replace is the starter because they cost a lot less to buy than a new tube. It is always useful to have a spare starter in your spare parts box anyway! If that doesn't solve the problem the next thing to check is the tube. Switch off the power supply at the main panel, take out the tube and shake it. If anything sounds "loose" inside then the tube itself may or may not be faulty but it is worth cleaning its contacts before finally scrapping it. Using a small craft knife or penknife, scrape the tube's contacts and the contacts in the light fixture to clean them so that they look nice and silvery. Replace the tube in its fixture, turn on the power and switch on the light.

If the tube still needs tapping or turning to make it light up then it should be replaced.

If that doesn't solve the problem then the whole light fitting should be scrapped unless you really know what you are doing and want to check the internal wiring for bad connections or, if none are obvious, maybe try replacing the ballast choke. But, unless you already have a spare choke taken from a similar lamp, it's usually not worth doing all that work because it may be cheaper - and much less trouble - just to buy a new light fixture complete with new tube, starter, choke all coverd by a whole year's warranty period! <><><>

As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.