A/C starts Cold then goes warm

[gosforth]

2005 Sierra, started blowing hot on the passenger vents only. Now blows warm on all dash vents. The truck can  idle in  hot sun & the temp stays at 40f (I have a thermometer in a vent) & at night it will stay cold.

I have

1) Changed out actuators

2) changed out low pressure switch

 

Now looking to change out the outside ambient temp sensor

 

Any suggestions will be appreciated. TIA

[Hillwood]

If you had the right scan tool,  you could pull HVAC codes, look at your actuator and sensor data. If you replace an actuator,  it needs to be calibrated with a scan tool. 

Playing the guessing game, I would say it is a temperature actuator. 

 If you have dual control there are 4 actuators in the system. Mode, recirculation,  left temp, right temp.

My advice is to get a proper diagnosis.  How much time and money are you going to spend throwing parts at it?

 

[bg1988]

On 5/25/2019 at 3:20 AM, gosforth said:

2005 Sierra, started blowing hot on the passenger vents only. Now blows warm on all dash vents. The truck can  idle in  hot sun & the temp stays at 40f (I have a thermometer in a vent) & at night it will stay cold.

I have

1) Changed out actuators

2) changed out low pressure switch

 

Now looking to change out the outside ambient temp sensor

 

Any suggestions will be appreciated. TIA

 check the evaporator make sure it's clean a dirty one will start out cold and warm up the air after

 

 

Try the water test   spray water on the condenser and if it stays cold while doing it, the refrigerant is low  or the condenser is very dirty

 

 

Don't do it if the condenser is hot  only upon a cold start in the daytime is fine I used to do it on my Wbody before a long trip to get the a/c working i did not want  to bother throwing money at it