Does your “parts unit”
have that same valve?
If so
measure the ohms of resistance between the two electrical spade lugs,
and from each of the 2 lugs to the metal body of the two valves.
The web link TJP helpfully gave you has the Troubleshooting on page 7.
From what you have written,
and what is on Page 7,
there is still a good chance the root of the problem is in the control board electronics or bad wire insulation.
Maybe do an internet search to see if any Forum somewhere contains Econar geo heat pump owners.
the resistance may vary between a charged system and one that is not
I would also think if the problem was on the board the fuse would blow whether the switch/valve was hooked up or not.
I do like the idea of checking the resistance between the each of lugs and the switch body.
If they are both open to the switch body, the check between the two lugs to see if they are open or shorted to each other.
One question that is important.
If the lugs are not grounded to the switch body, can you hook up the wire
FROM the control board while leaving the other disconnected and not blow the fuse?
I am thinking that is a "switch" that goes open or closed depending on the pressure it senses. By doing so it then turns on or off a relay or two that controls other components. 2 amps is not a lot so whatever is connected is not drawing a lot of current.
BTW I am not an A/C guy so i am flying by the seat of my pants on the above suggestions
