We are a small HVAC company. Received a certified letter today stating that one of our customers homeowners insurance company is suing us.

We live in Iowa with very cold winters. Our customer goes to Florida and leaves house vacant. We preformed a service call on his thermostat -(just switched fan control to auto from on position-did not touch furnace. This was in April.

February of following year while they were in Florida for winter, the heat quit (25 yr old furnace-and told them 5 years ago they should replace) and the water pipes burst (they did not winterize house)

Their insurance company letter states that we are at fault since we serviced furnace. Suing for 93,000 in damages.

Can they do this and are how can we possibly be liable??

Thank You in advance for your help.