If they are run at a higher voltage they burn out faster.
Low voltage lights not working. Post a picture if you are not sure. It is common for landscape lighting to stop working and usually a simple repair can bring yard lights back to life. One of the lamps stopped working and I bought a new one and now the whole system does not work.
Cut cable or short. If they run at a lower voltage they are dimmer and tend to go black because the Halogen Cycle does not work well and tungsten is deposited on the bulb glass. If you do have power at your transformer and the lights still arent turning on there is likely a short causing the transformer to shut off.
If they do replace the. Is this a transformer problem. Transformers can also use a fuse and or a reset circuit breaker switch.
Installing high watt lamps that are not specified for the track light head. Do you mean low voltage eg 230vmains or extra low voltage eg 12volt. Have 12 low voltage hampton bay spot lights hooked up to a hampton bay transformer also have 3 rab lighting brand flood lights that are not low voltage hooked up to the same transformer.
The customer said the bulb burnt out and then they replaced it. And debug the circuit. Is this controlled by a dimmer.
If one appears loose you must disconnect the power source and then unscrew the wire-nut connector. The Entire Lighting System Is Down. It worked for a while and then stopped working then started again and now it died completely.

