cycyling usually occurs close to the end of a hid lamps life,when the pressure in the lamp rises too high,and the voltage needed to sustain the arc is higher than the voltage provided by the ballast,when the lamp cools down the pressure lowers enough for the ballast to strike the arc the lamp once again warms up and the process repeats itself.high pressure sodium lamps dont loose many initial lumens but cycle relentlessy at the eol until the lamp or ignitor fails,mercury vapor lamps usually cycle then continue burning for a long time.

It's more rare to see cycling MV and VERY rare to see cycling MH (they are shut off at EOL of they explode  ), but when they cycle, it's pretty similar to HPS lamps (example of cycling MV here ).

i've seen a metal halid ;De cycle in a high bay fixture at my school's gym,they replaced it fast.

cycyling usually occurs close to the end of a hid lamps life,when the pressure in the lamp rises too high,and the voltage needed to sustain the arc is higher than the voltage provided by the ballast,when the lamp cools down the pressure lowers enough for the ballast to strike the arc the lamp once again warms up and the process repeats itself.high pressure sodium lamps dont loose many initial lumens but cycle relentlessy at the eol until the lamp or ignitor fails,mercury vapor lamps usually cycle then continue burning for a long time.

Correct How ever Cycle Free HPS are becoming popular know so you can identify that a bulb is out or a ballast is out, (hint)the fixture need to be looked at for any problems.

In my job, sometimes I travel to other factories or small machine shops and notice that the 400w high bay MH is very popular. I also notice sometimes they cycle, and the reason for most of the cycling is because the arc in MH lamps is sometimes unstable...it seems to gyrate or swirl like a tornado. The swirl builds momentum until....poof! it goes out. Then has to restart and go thru the same thing again. Also, I have a 175w MH flood at work (horizontal bulb) that will cycle when lamp gets old. It's done that with a couple different lamps.

Metal Halide's cycling are becoming more common because i have seen about 5 cycling in the past week or so! My Westy MH lamp cycles!

when a metal halide start cycling its best to replace it as soon as possible,to prevent passive faliure.

it would of been easier to say "replace ASAP it before it goes boom" 

actually i've seen a metal halide lamp cycle,the arc started swirling more and more until the lamp went out.

I recently saw a cycling MH in a square recessed fixture over a drive thru window at McDonald's, weeks before it began cycling, it was doing a lot of fickering for a few weeks and just recently started the cycling mode...

At work I've seen plenty of cycling MH lamps, and at the same time plenty of ones that have exploded. I havent seen many cycling MV lamps.

My Caster 175W MV cycles in the Heath/Zenith bucket light it came with, but runs fine in one of the powr/bracket type fixtures I have.

My Caster 175W MV cycles in the Heath/Zenith bucket light it came with, but runs fine in one of the powr/bracket type fixtures I have.

i was thinking that happens because of magnetic saturation.

or possibly because these yardblasters typically run lamps around 150 watts.

Where I live in Queens, NY, cycling HPS lamps are an epidemic, and I HATE IT!!!!  It is SOOOO annoying.  That is why Mercury Vapor should NEVER have been banned!   

Where I live in Queens, NY, cycling HPS lamps are an epidemic, and I HATE IT!!!!  It is SOOOO annoying.  That is why Mercury Vapor should NEVER have been banned!   

some HPS Lamps i see dont Cycle....but instead Go a Dim Orange Color and just Flicker.