I have a two year old Ruud heat pump 3 ton outside unit that's giving me a high pressure shutoff light. The outside unit stops operating while the handler just runs nonstop.

When the unit was first installed, it ran perfectly for 6 months. I installed a programmable stat on my own and had some issues getting all the settings correct. I take responsibility for that. In the meantime of getting it all straight, my HVAC guy said that the thermal expansion valve was bad, and he replaced it and added freon. Since then, starting about a year ago, I've had trouble with this shutoff deal. It only happens in mild weather (40-75 degrees)where we have cool nights and warm days that require the use of both the heat and AC in a short period of time. It's the switch from one to another that seems to make it angry.

Once the summer starts, it runs problem free for months. At first it seemed like something I could live with, but it's getting pretty annoying and I don't want any further damage. I also can't afford to keep paying him to come out and not fix it properly. I have another 2 ton equivalent unit in my house, and I've never had a problem with it.

I've done some searching and others with similar issues were told it could be that the system was overcharged, or a switch was bad. Any suggestions on what could be causing this?