Fluorescent Light Fixtures-Inconsistant Operation

Great question! In general, the 8' lamp has no starting aid except for high voltage. If you still have magnetic ballasts, then the "flick" (when done near the peak of the AC sinusoid) will cause an inductive transient that boosts the voltage for a few microseconds. Unfortunately, that is difficult to do by hand because the incoming power is a moving target at 50 or 60 cycles per second.

The newer electronic ballasts don't provide this little boost.

There are two things you can try to help the situation. The first one is easier and cheaper than the second.

First, you can provide your own starting aid directly to the lamps. Some manufacturers have actually sold lamps with this applied and many people had no idea what it was all about. So, first I'll tell you what it is and then I'll explain it. You can read about starting aids in lots of technical literature if you like. It consist of a conductive (metallic) strip applied directly to the lamp from one end to the other (but not touching the metal base) in the form of a tape. This is the same tape used to detect broken window glass. Or you can get some copper tape from your local stained glass store.

The way this works is to allow a build up of ionized gas by capacitively linking from each coil (electrode) through the glass, and then through the tape down to the other end where it capacitively links back to the other coil. The wider the tape, the better the linkage. But I have also done this with a piece of wire taped on from one end to the other. A lot depends on the proximity of the coil to the conductive surface on the outside so you might want to shadow box the ends of the lamp to figure out where the ends of the coils are closest to the glass. Capacitive linkage depends on distance and surface area.

The second way to do this is more likely to work but it may cost a little more unless you just happen to have this stuff lying around. What you need to do is to temporarily or permanently boost the supply voltage to the ballast circuits. This will help even as the humidity rises (more on that in a second). If your line voltage is supposed to be 120 VAC there is a 10% tolerance band which the power company is supposed to keep within. That means that all your devices should operate anywhere from 108 VAC to 132 VAC. Your ballast is also supposed to be designed to operate without any problems within that range as well. But the lamps always start faster when you are in the higher end of the tolerance range. So if you increase the line voltage to the nominal value +10% they will always start. They may also be a little brighter and run a little warmer due to the increased supply. Once they start, you could drop back down to nominal. It all depends on what you want to do.

If the glass accumulates water vapor from high humidity it can offer a capacitive linkage (when attempting to start) with a high enough resistance from one end to the other so that it has the opposite effect of the starting aid mentioned above. One of the ways to combat this humidity problem was to apply a chemical similar to silicone (or car wax) that would cause the water to form droplets that were not connected, thereby preventing the starting problem.

Either solution mentioned above should help but the voltage boost will work best.

Before a lamp starts, the open circuit resistance in in the mega-ohm range. As it begins to light by ionizing gas inside, the resistance drops very rapidly to just a few hundred ohms. The trick is getting enough ionization to happen so that it creates a more conductive path from one end of the lamp to the other. I'll be watching to see how you do.

You didn't mention whether your fittings had iron core ballasts and starters or electronic ballasts,,did you?

Assuming the former....

The lightswitch flick trick is the big clue here.

I reckon some of your starters are stuffed and will need replacing, or some of the tubes have open circuit heater elements which can be remedied by reversing the tube in the fitting so the heater element at the other end (unless both ends are expired) can do the starting preheat.