I have a 250 watt ceramic metal halide that uses a high pressure sodium ballast it shut off the other day and now it will re light but only for about three or four minutes then it shuts down it will fire again when it cools down what would it be bulb cap starter or ? It is all close to new any way to test any of these parts ? Thanks Rad

Are you saying you are using a MH lamp in an HPS fixture?

If so then that is your problem.

No it is a ceramic metal halide it is built to run on a hps magnetic ballast it is a retrofit it will fire but it will go out about the time it seems to reach full power and it will attempt to fire several times before it will fire everything looks good no burning on the lamp or ballast the bulb still looks new inside not that it means much

Can you provide the make and model number of the lamp and ballast?

I don't know about the ballast it was a kit that I bought used it is a magnetic hps ballast with a starter, cap and transformer it did work right for a couple of months, the bulb is a ceramic metal halide phillips 250 watt horizontal burn and I am running it horizontal. It will fire and just when it reaches full illumination it shuts down, maybe the bulb is bad Idk the bulbs are about 70 bucks to buy so I kind of didn't want to spend the money and find out it's not the bulb maybe I will just spend the money on a hps bulb for it to test the ballast they are only about 12 bucks and I could just put it into use but it don't work as well as the ceramic metal halide I do indoor vegetable gardens during the winter and supplement my small greenhouse with hid lighting and a small kerosene burning smudge pot to keep it warm, the ceramic metal halide works much better than hps or standard metal halide I need to get this fixed because my spring starts are just around the corner and all my t8 are being used to replace cmh anyone know how to test the ballast I have a very nice multi meter I just don't know how to do it thanks in advanced Radralph

Cannot mix types of lamps and ballasts, need to be a matched set, either metal halide or HPS.