A broken steam iron does not necessarily mean you need to buy a replacement. Most steam irons are relatively uncomplicated, and often the problem can be resolved with part replacement or even a thorough cleaning. Oster irons in particular feature a temperature indicator for safe storage, a non-stick soleplate and a variety of settings. Some also offer a self-cleaning option, though if you've been having trouble with your iron you should try cleaning by hand. If the problem is internal or electric, you should either consult a professional or replace your iron; it may be less costly than rewiring internally.
Unplug the iron and make sure it is cooled. Some Oster irons have indicator lights letting you know when it is safe to handle or store the iron.
Give the iron a deep cleaning. Iron cleaning gel is available to remove built-up grime from the soleplate. Apply the cleaning gel and use a sponge or steel wool to scrub the soleplate, allowing the iron to cool again and use a toothpick to remove any residue from the steam vents. For the steam valve you may need a needle to pick out mineral deposits.
Flush the water tank. Undistilled water can eventually damage the iron. Use equal parts vinegar and warm water to clean the tank by steaming over the sink or a strainer, then use filtered water in the future and drain between uses.
If your iron is still heating erratically, it may be a problem with the electrical cord or thermostat. Check several outlets and adjust the thermostat to determine the problem. Replacement cords and thermostats are available, ranging from $20 to $50 dollars depending on model. Contact Oster about replacement parts to decide whether it is more cost effective in your case to repair or replace.