my closed loop system has 3 wells and normally works very well. System very effectively heats and cools my home wonderfully, however, every summer since it was installed approximately 4 years ago it stops cooling without warning. The installer comes out and tell me that the "pressures were off" and they had to adjust them. My thoughts are that if the pressure is constantly getting low, there must be a leak of some type somewhere. He tried to tell me that I need to get regular maintenance as this is just like owning a car. I explained that maintenance is one thing, but if my car completely stopped working every summer, I would trade it off, but kind of stuck with my geo unit. Is anyone else experienced anything like this.

Get on a semi-annual preventive maintenance contract with a knowledgeable provider. Presumably your car gets regular oil and filter changes, tire rotation, etc.

That said, a periodic loss of loop pressure needs to be addressed; we'd need to know a fair bit more about your system to advise.

Is the unit showing any faults on it?

"Pressures were off".....That could be a couple things.
If it is low on coolant "AKA Freon" then that is a fixable leak.
If it is a leak in field, that might not be fixable unless it is at a connection. If it is a unfixable field leak you could add a pressure tank that would store extra field antifreeze and makeup the loose over time so it doesn't shut off so often.

Also if there is a gauge you could watch that so note its pressures over time and maybe guess when it is going to stop next and fill it first.

I would also like to apologize for the comments in the other thread you posted....pretty frustrated with the unprofessional responses.

Have a great day.

Loop or refrigerant pressure issues is nothing regular maintenance would prevent, nor should it recur.

Also not sure how extra loop field antifreeze would prevent shut offs in A/C mode?

Does it stop at initial start-ups? a GT contractor has used johnson variable speed control on a dual pump, having one pump off in cooling and varying another pump by connection to refrigerant pressure/temperature - conditions . This controlling device is attached to the refrigerant port off of a 'T' and works nicely just like a regulator for loop flow when the loop starts in summer way too cold . That mentioned, reason here, the GT starts way too cold at the loop for starting cooling is it is on a 230+ ft per ton loop that is better than average for heating running efficiency and savings.

About reservoirs mentioned above: late 1980's Tom Dellinger of TETCO, then Delaware, OH- did have dealers put only a reservoir off of the line coming in from the loop. A 'T' fitting not only caught air bubbles to eliminate nuisance re-flushing and re-pressurizing/filling entrapped air usually associated with new-ly introduced fluids- - Pumps received fluid from the low end of the side-ways-mounted 'T'. Reservoirs- those 5 gallon - 'carboy' plastic tanks up in joists easily allowed for observing speed of any unwanted (should not have been allowed-to) occurring 'leaks'. -Later some noticeably slower leaks of like refilling a gallon a year were thwarted by a couple tablespoons of common fine table pepper... -Reservoir at about 5 to 6 ft above the pumps seemed workable up to within 16 feet BELOW the highest part of a ground-loop (or interior loop plumbing) in-position relative to the reservoir tank. Loops operated as still today with very nice net pressure(s) in to pumps, and are found at only 2 or 3 pounds of 'standing' liquid pressure. When "on" the pump always has a nice positive inlet pressure.

GT contractors still retrofit these to 'closed- higher - pressure - loops' for a few hundred dollars.