Modification of a/c thermistor readings for colder operation

I have an 02 pre runner with 3.4l and I would like to modify my a/c thermistor resistance reading to my a/c control head so I can get it an extra 5-10 degrees colder without freezing up my evaporator. The coldest reading that I can reach with my stock unit is 40f on max and 45f-50f on normal and that is with a 90 degrees ambient temp . refrigerant circuit is charged at 1.43lbs and I have evacuated and flushed the system so I can have a correct measurement when I replenished the oil amount. High and low side pressures are within specs and all the components except the a/c control head are less than a year old, I am the original owner and I know the system can get colder than what it is giving today , I have researched this and I tried a 20k ohm resistor but did not see the results I was looking for. I am thinking of installing a variable resistor switch in series but I figured it would never hurt to ask if anyone out there has had success with this and could share the correct ohm resistor readings or some where in the ball park. This is my first time on any Forum but Any feed back would be appreciated if it can help me reach that temperature goal......

 

Is your 40* at the center nozzle?

If so the face of the evap is likely at 34-36*

I dont think you have enough slack to drop the thermistor value w/o causing icing.

 

Welcome!

 

Welcome to TW !!

 

Welcome to TW!

 

Thank you for the warm welcome fellas. Thank you for the input Clearwater Bill. To answer your question... Yes I have taken all the readings from the center vents with the side vents closed. If I am reading 40f at the center vents and if the evaporator face is 34f-36f then could there be a possibility of the heater case flaps not engaging completely causing warmer air to blend in with the cold making that extra 5 degrees difference. I have never removed the heater case but I have function tested the blend air flap actuators and they seem to have full range of motion and don't seem to be binding. I have noticed bleed off through the defroster vents when the humidity level is high causing condensation on the windshield. I have been contemplating removing the heater case and replacing the foam sealer. The only reason I am assuming this is the amount of black spongy foam that has come flying out of the vents in the pass couple of years. When I get a chance to actually rip out the heater case I will replace the heater core and whatever actuators are accessible. Would you happen to know if there are any cable adjustments that can be made to make up any of the slack on the heater case flaps? If so your input would be much appreciated. Thank you