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2 2005 Chevy Trailblazer extended climate control and AC questions

I have two questions, if anyone is willing to answer them, about a 2005 Chevy Trailblazer extended.

  1. My AC reads 45psi on the low side, which my can of r-134a says is ‘full’, yet the air isn’t coming out very cold. Under the hood, it says I need 1.8 lbs for front and 2.65lbs for front and rear. What is ‘front’ and ‘rear’? I thought I just put the r134a in the low end until it reads about 40-45 psi. The can of r134a I have is only 1.2 lbs I think, but the car is at 45 psi when running max cold AC. Can someone please explain how this works and how much to add and how the psi figures into all of this?

  2. I believe there is something wrong with my climate control system in this trailblazer, but am not sure what it is or what to do since I have never had a car with dual climate control. The drivers side always spits out hotter air than the passenger side. What would this be and is it something that I could fix myself fairly simply? I assume it is just a sensor. Am I correct?



Front and rear means the vehicle has two evaporators. One in front under the dash and one at the rear of the passenger compartment. If it does have two evaporators the system will require more refrigerant because of the extra evaporator.

When charging an AC system, the idle speed should be raised to 2,000 RPM’s and a large fan blowing on the condenser at the front of the vehicle. This simulates the vehicle being driven down the road.

The difference in temperature between the passenger and driver side might be caused from a malfunctioning blend door/motor.


Is your AC working at all?? I ask because that 45 psi is with the compresser engaged. If the compresser is not turning on, you will not get am accurate reading.