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Jan Andersson
Jan Andersson, ASE Master Tech
Category: Chevy
Satisfied Customers: 834
Experience:  20 years of general automotive repair & modification. Chevy owner.
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Chevrolet Tahoe LT: My 2002 Tahoe rear a/c blowing hot air.

Customer Question

My 2002 Tahoe rear a/c blowing hot air. Front a/c working ok
Submitted: 1 year ago.
Category: Chevy
Expert:  Jan Andersson replied 1 year ago.
Hi, I start all AC diagnostic work by checking the charge level. I evacuate the system and see how much (by weight) refrigerant was in it. In some vehicles a low charge would show up first in the rear AC unit. Since you have replaced the orifice tube and accumulator (receiver dryer) I can assume that the charge level is ok? I have also replaced several rear expansion valves on this series GM vehicles. They seem to get stuck over time or just quit working, not allowing refrigerant to pass. The orifice tube only makes cold for the front AC. The rear has an expansion valve of it's own for making cold. I would guess this is what your problem is, just based on the number of expansion valve failures I have seen. It could also be the cold/hot blend door that isn't working. When you adjust from hot to cold and back, does the temperature change? I mean, do you get HOT air when its set to hot, and just warm, ambient air when its set to cold? Or is the air HOT in both settings?
Customer: replied 1 year ago.
Have not checked that
Expert:  Jan Andersson replied 1 year ago.
OK well let me know what you find, and we'll go from there. I will be online off and on tomorrow, depending on my day job workload.
Customer: replied 1 year ago.
Where is the valve located and can you send a picture
Expert:  Jan Andersson replied 1 year ago.
The rear AC and heater cores are behind the left rear interior panel. Get the panel off, then you will see the housing. All the instructions say you need to REMOVE the whole assembly and take it apart to get to the expansion valve, but I could swear its possible to replace it without taking the housing out (and thus needing to remove the heater core and heater hoses to do it). I am not 100% sure. It has been a while. The front AC does not use an expansion valve, it uses a fixed size orifice tube, which has a screen that can get clogged up with dirt. It is located inside a refrigerant line, at a joint where two lines are connected together. Its one of the lines going to teh evaporator through teh firewall, the O-tube split will be in the engine bay. The location is not marked, but if you look closely, you will find a section at the joint where there's a straight part of pipe, and maybe 3-4 inches from the joint the pipe has two small dimples on it. Those are there to prevent the orifice tube from sliding in too deep inside the pipe. They are often hard to get out, there is a special tool but very thin needle nose pliers will pull them out. They sit tight in the pipe, sealed by an o-ring thats part of the orifice tube.
Expert:  Jan Andersson replied 1 year ago.
I'm sorry, RIGHT rear interior panel, when you are looking at it from the rear of the vehicle.
And the expansion valve is indeed hidden inside the evaporator housing, as this video will show you:
https://www.youtube.com/watch?v=WjzsdQGdxN4
Jan

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