I have an old GE heat pump (over 20 years old) that is I think about a 2 ton or 2.5 ton. The problem is that the A/C aspect is not working right now. I came home the other day to a very hot house. Seems the A/C was putting out heat.

So... I shut it off. Then tried it again later. It comes on cold. The pipe going into the house is adequately cold. However, after about 5-10 minutes, you'll hear a click... small at first, then every couple minutes, there's another... and the click will be louder, and I can feel a shock through that pipe. The click _I think_ is the solenoid on the reversing valve giving way just for a moment almost to the heating position... then re-enagaing. Well after about 3-5 times of that, the thing finally goes into complete reverse, back to heating... and tends to stay there. Shut it off... restart... is cooling again.

Solenoid is 24v, 12 watt, 50/60Hz

The solenoid is rather hot when all this is going on. Possible solenoid is just old and bad? Or.. Possible the guy rewiring the contactor has 120v going to it instead of 24v that's the spec? Low freon able to cause this? Defrost board bad? Bad ground? The horror... The horror... of not knowing. Something inside, under the house at fault? This installation has the coils inside the house in the crawlspace duct work, and unit, the heat pump is outside. I can repair a solenoid, or board, but not a reversing valve or recharge, etc, of course.