Our Geo unit will run a few cooling cycle in the morning normally - quiet and cool air, but then starts running loud and has little to no cool air. The unit looks to be freezing up as you can see the frost on fittings and on opening the unit up its covered in frost. The HVAC unit that supplies air to it has clean filters - my only guess is that I don't think the unit is kicking into high speed when we turn the air conditioner on. Could that be it?
This needs some clarification. You have a compressor and a fan (and a bunch of other stuff). The fan can happily blow air around all on its own - whether or not the compressor is running. Is the compressor running well and some point then not well at others? Or is it only running noisy? Air flow is one issue (dirty filter, too many vents closed, etc.). Refrigeration leak is the other issue.
The compressor seems to be running fine. The first few times it runs in the morning, the system runs nice and quiet and generates cool air, but as the temp rises outside the unit struggles to keep up and begins to freeze over. The fittings in the unit frost over as does the cooling fins in the air handler (not sure what the right term is for it). My technician feels like its an airflow issue and wants to speed up the air handling unit. How is that done? Is the speed adjustable? Doesn't appear to have a gas leak as the first few cycles seem fine.
I hope the technician has measured refrigerant circuit high and low side pressures and temperatures and calculated superheat and subcooling. Absent that data, he / she is not entitled to "feel like" anything, let alone air flow. If he / she has assessed refrigerant circuit conditions (2 pressures + 2 temperatures) and found them to be within spec then it is appropriate to consider air flow issues. The investigation would start by assessing static pressure across the air handling unit, followed by inspection of coil and air filter for excessive fouling. If both are clean but static is high then undersized ductwork (supply, return or both) may be to blame. If the system worked well in the past but has now deteriorated, then the problem is most likely not duct-related, unless Larry the cable guy got up in the attic and stomped flat some ductwork. Most icing problems this far along in the cooling season, absent horribly fouled filter, coil, or blower wheel, arise from refrigerant circuit problems - charge or metering device causing depressed saturation conditions at air coil. Any tech able to fog a mirror, see lightning, and hear thunder ought to be able to work through the above analysis in under an hour and set forth necessary repairs. if not, find another.
