Tri Cities Temperature Control

We had a maintenance problem with an air-​conditioning system they installed years earlier. Our cooling system was only blowing hot air, but on an intermittent basis.
Over the course of six months, we had four different maintenance calls for the same issue. Their techs could not diagnose the problem the first three times, even replacing parts that were obviously not broken, and charging for everything. After several hundred dollars, the fourth visit finally fixed the problem.
We protested having to keep paying in full each time they charged us with no results. We were more insistent after the fourth visit, and finally the agreed not to charge us for the last visit, but told us to take our business elsewhere in the future.
I feel they do not stand by their work.