Just installed 2ton 16 seer keeprite i ho set the t stat to cool but the unit won't start... I press the contactor outside the unit and the unit work , change the t stat still not working made a jumper still not working. Appreciate all the help you guy's could give me
Did you give enough time for the t-stat to respond? Some have a delay up to 10 minutes before letting it start... Did you try putting the two wires together at the t-stat that would normally close the contactor? That's one way of ruling out wiring faults?
You could also try disconnecting both the low voltage wires at the contactor and twisting them together and then doing some continuity checks at the other of the wiring. Look for any splices.
How many low voltage wires are going to the outdoor unit? Some units require the R wire as well as the Y and C. Also there could be a pressure switch fault that's preventing the AC from starting.
Also check the terminals on the subase. If there is a RC and RH terminal make sure to put a jumper between them or there won't be 24volts going to the contactor coil outside.
'Trainerguy