window AC unit: what should the temp be at the evaporator and what should the low side pressure read?
Answers:
A direct answer to your question is 20 degrees below room temperature at the output port of the a/c and 65-75 lbs. on the low side.
The best test for any window air conditioner is the "20 degree test". With the unit turned on for at least 5 min. and the control set for high cool , check the temperature of the air coming out and the temperature of the air going in(room temperature). There must be a difference of at least 20 degrees between the two readings. If you do not get at least 20 degrees difference there is a problem with the a/c.
The last thing that you want to do is cut into the sealed system because you risk the possibility of contamination and create a potential source of a leak.
I would say that more than 75% of the window a/c calls that I go out on where the customer really really thinks that it needs "freezone"(the customer's name for the refrigerant) I find the unit is undersized for the "heat load" or improperly installed or the condenser or evaporator coils are blocked with dirt. Very few actually need to be recharged with refrigerant.
Other answers:
a better way to check it is by temp. drop. The air coming out should be 15 to 20 degrees cooler than the room air temp. if it falls within these temps, it's ok
a better way to check it is by temp. drop. The air coming out should be 15 to 20 degrees cooler than the room air temp. if it falls within these temps, it's ok
i agree with appelpro as long as you are getting at least a 20 deg drop across the coil . temperature & pressure will vary depending on the refrigerant.