Pressure switches aren't that expensive, and installing/replacing doesn't require a degree. 12 years is long enough to consider a heater "old". Having said that...
Did they inform you immediately when they broke it? Or did you discover it. THAT would be one of my considerations on deciding whether or not to go after the company.
Winterizing is a service where you go in assuming everything is working properly, unless otherwise informed. As a tech, It can be a virtual "mouse trap". Sometimes it is unavoidable, you may have to give the benefit of the doubt here.
WADR, It is easy to place blame by saying "It worked before".
You/we need more information about the circumstances surrounding the break. What were they doing that caused it to break? Were they handling the switch properly? or did it get hit or knocked. Sometimes you can't tell something is going to break until you begin to work on it. If they were in fact working on the switch, and it fell apart, maybe the company would be willing to split the cost in the interest of good customer relations? If it looks as though it was hit or knocked while working on something else, you have to look at the condition of the switch, was it corroded and look like it would break if you touched it? Or did it break due to mishandling?
There really is a lot to consider. Without pictures, or both sides of the story, none of us here can really comment responsibly one way or the other.
