About 6-7 years ago we had two new heat pumps installed in our house. The house was about 20 years old at the time, with the original heat pump units. One of the heat pumps has worked very well, but the other one developed a leak in the coil after just a few years, and they had to replace the coil. The coil went out again last summer, and was replaced again. Both times I had to pay labor charges, even though the unit was under warranty.After the second replacement, the coolant was still leaking, and this time they blamed it on the lines, so we had them replace all the coolant lines to the unit. Again, a very large expense.So far, since then it's working well, but we have probably spent the equivalent of the cost of a new unit, mostly in labor charges, since the parts were under warranty.After the coolant lines were replaced, the technician said he couldn't figure out how to program the thermostat (that they installed originally), and the unit was only heating, not cooling. Another technician came out and replaced the thermostat, which seemed to have fixed the problem.Fast forward to fall. We turned the thermostat to heat, and it's still blowing cold air. They send out a technician, who does something to get it to heat, but now the weather is hotter, so we switch it back to cool. I come home from work, and one side of the house is nearly 90 degrees, and the other side must be close to 50 degrees. The heat pump was still heating in cool setting!Another technician is sent out, who spends quite a bit of time trying to diagnose it, and finally says it's some board that needs replaced. When I question that, he said he was sure it was that board, but that just didn't seem right, since it could heat, and it could cool, but the thermostat signal was not controlling it. He said it was going to cost nearly $500 for labor to replace the board, since the part was under warranty. I don't see how replacing a board could take more than 1/2 hour of labor, since they're all very accessible, so why so much?Since I wasn't convinced that it was some burned out board, I tried diagnosing it myself. After some research on the wiring diagrams for the units and on how heat pump controls work, it seemed like it should be the blue wire that controls switching from cool to heat that's the problem. Sure enough, the blue wire was always ~24V on heat or cool mode.I thought it might be the thermostat that they installed, so I reinstalled the old one, and it still had the same problem. In doing this, I noticed that the blue line had 24V on it, even when the thermostat was removed, which didn't seem right, so I disconnected the other end of the wire to see if it was coming from the compressor. The line still had 24V on it, even with both ends disconnected! Obviously it is being shorted somewhere along the run, probably caused by damage done to the wire when the coolant lines were replaces, which is when this problem started.I connected the blue wire to the compressor through an extra wire in that cable, and now it's working perfectly.I am better trained trained in electronics than your average home owner, but what I did is not rocket science, and any trained technician should have performed the same steps and come to the same solution. What really upsets me is that one of the technicians switched the unit to cool. The only way that could have worked is if the blue control wire was removed, or it was wired to some other random wire. They had to know that it would not work when switched to heat, but they did it anyway for some reason.I now have 0 confidence in Alaskan, and, even though I still have some time remaining on my warranty, I will be using another contractor from now on, which will likely save me money in the long run.