Performed diagnostic on 4 year old unit. Homeowner states downstairs unit is not cooling, has not been cooling since Saturday. Cycled system for cooling. Indoor unit kicks on, outdoor unit is unresponsive. Outdoor unit is not recieving low voltage command. Found low voltage wire to condenser had came off the indoor circuit board. Re-stripped wire and re-connected to board. Cycled system, condenser kicks on normally. System is cooling upon departure. Recommended adding surge protectors to units to protect from any electrical failures or possible problems. Needs to talk it over with husband. Renewed ESA maintenance program, wants to keep it on yearly basis.