Problems with tubular fluoresecent light

[RetiredAt63]

One of my grow lights is not working properly.  It hums, the bulbs don't always come on - sometimes I loosen and tighten and they come on, sometime I turn it off and back on and it comes on, sometimes it takes both and a lot of playing with it to get the tubes on.  Is this old bulbs, bad ballast, bad connections, more than one of the above?  It is difficult to get the light unit out of the plant stand, so I am hoping it is an easy fix.

The other light unit in the stand works fine.  Same age, same age bulbs, etc.

[paddedhat]

If the lamp is starting to turn black on the ends of the glass portion, it's probably near the end of it's life. Easy way to find out is to switch the lamps and see if the problem goes away. If not it could be anything from loose wires, or lampholder, which is unlikely, to a bad ballast or starter. If you have starter(s) they will be evident. You will see round openings in the fixture with small aluminum cylinders in the openings. They come out by turning them slightly counterclockwise, and pulling. They are not too common in newer fixtures, but the first thing to fail, in older ones. If it's the ballast, new ones are available, and reasonably easy to change.

[Arktinkerer]

Used a lot of these in the garage/shop.  Hate the darn things.  When they get cold they have trouble starting.  Cheap units in the big box stores blow the ballasts when they get too hot or too cold. 

Went over to the LED bulbs from Sams or Costco.  Not much more expensive but they turn on every time and I haven't had to replace a bulb.

[guitar_stitch]

If the metal shield is too far from the bulb, it won't fire.

If the starter (if equipped) is bad, it won't fire.

[PlainsWalker]

Dust build up on the bulbs with a bit of moisture to make it conductive can make fluorescent lighting not work right. Quick and easy issue to check for and fix.

[RetiredAt63]

My temporary plant stand is shop lights, but this is a dedicated plant stand, should not be these issues.  Plus it is in the main living area, not too hot, not too cold, and the other unit is fine.  LED bulbs look fine for our eyes (and I have lots in the house) but not enough light for plants.  Eventually, I hope.

Used a lot of these in the garage/shop.  Hate the darn things.  When they get cold they have trouble starting.  Cheap units in the big box stores blow the ballasts when they get too hot or too cold. 

Went over to the LED bulbs from Sams or Costco.  Not much more expensive but they turn on every time and I haven't had to replace a bulb.

[RetiredAt63]

Nothing has moved physically.  Sometimes it starts, sometimes it needs encouragement, and sometimes it makes a loud hum.  Does that sound like the starter?

If the metal shield is too far from the bulb, it won't fire.

If the starter (if equipped) is bad, it won't fire.

[RetiredAt63]

It is the bottom unit, so it could be collecting more dust (and fine soil dust from the top unit).  Apart from the bending and twisting and careful kneeling (bad knees) that make it less easy, what should I do to check?  Take the tubes out and clean them and the ends?  Turn the unit off and clean where the tubes go in?

It is a plant stand, the plants get watered, the humidity is fairly high, so the moisture would definitely be present.

Dust build up on the bulbs with a bit of moisture to make it conductive can make fluorescent lighting not work right. Quick and easy issue to check for and fix.