Find contractors who are willing to guarantee their work. Most contractors are willing to give you a guarantee of work on things they install. However, not all contractors are so willing to give guarantees on repair work. You don't want to have to keep calling out contractors if issues arise. This means that you should specifically seek out contractors who will guarantee repair work to protect yourself against faulty repair jobs.

You should find online reviews for the contractor before you make a hiring decision. These online reviews will tell you a lot about the professionalism and skill of the contractor. If there are no online reviews to look at, ask the contractor for local references. Any professional boiler repair contractor should be willing to provide you with references. Any defensiveness over a request like this could indicate someone you don't want to work with.

Try to get an estimate before you let the contractor get to work. The estimate should cover everything from the cost of the project to how long it will take. Since repair work can be difficult to create estimates for, you should be willing to allow the estimate to slide around a bit.