Have an 18000 btu ac unit that quit working....try's to come on, but wont...now wont do anything. It was bout in 2004

You have to try resetting the system. First turn the breaker off for the condenser and wait about 20 seconds. After you turn it back on the system should reset. Air Conditioning Tamarac

R22= 70-80psig
R410a=120-130psig
Depending on many variables such as blower speed, coils clean, indoor/outdoor temps.

This is a fix it site. check your local kijiji or craigslist.

Read your manual

All Window A/C Units have the Model inside on top
of the evap fan housing

Look through the front grill on the left side

It's requires clean up , it's all covered with dust and that caused it to freezes and iced. It will consume more electricity when gets iced.

1) Test the main switch, can be shorted, or defective contact you must replaced .see the diagram attached. God bless you

divide your btu rating by 12000. (1 ton = 12000 btu)
For example - a 24,000 BTU Air Conditioner is a 2 ton unit. 24000 divided by 12000 = 2
A 18000 btu air condtioner is a 1 1/2 ton unit 18000 divided by 12000 = 1 1/2
you can find out your btu rating by looking on the tag on your unit.

Reverse the wires in the receptacle ,not the ground,this is most likely the problem the way the circuit is set up in the ac unit.Let me know if this helps.

The 18,000 btu A/C is 230 volts, are you sure the 12,000 btu unit is 230 volts most are 120 volts.
Usually 12,000 btu is the biggest 120 volt A/C you can buy.