new thermostat now the ac not working

More info needed to help.

Brand and model of thermostat. Type,brand and model number of equipment for starters.

it's a honeywell Model Pro 3000 single stage Honeywell thermostat TH3110D1008

How was the old one wired up and how is the new one wired up.

The same

Here is your wiring diagram fir the new stat

http://customer.honeywell.com/techlit/pdf/PackedLit/69-1846.pdf

What is the model and brand of the old thermostat?

With that info we can compare wiring.

NOTE: Is the jumper still on RH and RC?

There is a time delay for the A/C to come on. Did you leave the thermostat set to A/C for 10 minutes or more before saying it did not work?

Does the blower in the furnace come on when switched to A/C at the thermostat?

Did you check the breakers inside and the fuses outside to make sure there is power to the outside unit?


Thermostat note from the instructions.

Cooling system
does not respond
(“Cool On”
appears on
screen)
• Check for 24 Vac at the equipment on the secondary side of the transformer
between power and common. If voltage is not present, check the
cooling equipment to find the cause of the problem


• Check for 24 Vac between the cooling terminal (Y) and the transformer
common. If 24 Vac is present, the thermostat is functional. Check the
cooling system to find the cause of the problem.

Check for loose or broken wires between the thermostat and the cooling
equipment.

when shows 300psig. pressure when supply runining but compressor is not working?

when compressor is turn off so what is problem?