08 Tahoe Rear AC not blowing cold

[Dustin Jackson]

Hello guys, I have the temp controlled AC for the front and rear but I realized that the rear is just blowing warm air unless I turn on the heater then it blows hot air, but ever AC.

After doing some research I checked to see if the rear AC lines are getting cold after running the truck AC for a while and I found that the AC lines going to the rear of the Tahoe do not get cold at all.

What does this mean?

Is this is symptom of the expansion valve or orifice tube getting clogged? Or is this an indicator that the rear AC lines have been cut from the AC system?

I will be crawling under the truck this weekend to make sure that the AC lines look ok.

Any insight into how this system works would be greatly appreciated.

 

[Jolly Roger]

If Im not mistaken, the AC lines run under the pass side step bar and are notorious for corroding and leaking. Id start there.

 

[Dustin Jackson]

If Im not mistaken, the AC lines run under the pass side step bar and are notorious for corroding and leaking. Id start there.

@Jolly Roger If there was a leak wouldn't the AC for the front stop working also? Are the lines connected between front and rear? When I do my brakes I am going to inspect the AC lines but I just don't know enough about how the system works yet to properly diagnose it.

 

[swathdiver]

Hello guys, I have the temp controlled AC for the front and rear but I realized that the rear is just blowing warm air unless I turn on the heater then it blows hot air, but ever AC.

After doing some research I checked to see if the rear AC lines are getting cold after running the truck AC for a while and I found that the AC lines going to the rear of the Tahoe do not get cold at all.

What does this mean?

Is this is symptom of the expansion valve or orifice tube getting clogged? Or is this an indicator that the rear AC lines have been cut from the AC system?

I will be crawling under the truck this weekend to make sure that the AC lines look ok.

Any insight into how this system works would be greatly appreciated.

There are two actuators back there that need checking with a scan tool.

 

[Dustin Jackson]

There are two actuators back there that need checking with a scan tool.

@swathdiver I understand that actuator moves the blender door for the rear, my problem is that the cold does not make it to the rear AC system. The rear AC lines never get cold. Am misunderstanding what an actuator is?

 

[swathdiver]

@swathdiver I understand that actuator moves the blender door for the rear, my problem is that the cold does not make it to the rear AC system. The rear AC lines never get cold. Am misunderstanding what an actuator is?

No, I don't think so. The actuators control the modes and temperature but I think the lines should be cold. @91RS @Scottydoggs

 

[Dustin Jackson]

No, I don't think so. The actuators control the modes and temperature but I think the lines should be cold. @91RS @Scottydoggs

@swathdiver I tested the Rear AC and I can switch between HOT and luke warm (supposed to be cold) and switch between top and bottom vents so I am confident the blend doors all work but the lines definitely do not get cold.

My next step is to verify that the AC lines are intact and haven't been spliced off by a previous owner, if everything looks OK I was going to replace the rear expansion valve and Orifice tube and recharge it from there. Any additional input would be great, thanks for the help.

 

[swathdiver]

@swathdiver I tested the Rear AC and I can switch between HOT and luke warm (supposed to be cold) and switch between top and bottom vents so I am confident the blend doors all work but the lines definitely do not get cold.

My next step is to verify that the AC lines are intact and haven't been spliced off by a previous owner, if everything looks OK I was going to replace the rear expansion valve and Orifice tube and recharge it from there. Any additional input would be great, thanks for the help.

Called in the guys who know more about AC systems than I do, which is not much! Do you have a subscription to AllDataDIY for the shop manual and troubleshooting guide?

 

[Doubeleive]

@swathdiver I tested the Rear AC and I can switch between HOT and luke warm (supposed to be cold) and switch between top and bottom vents so I am confident the blend doors all work but the lines definitely do not get cold.

My next step is to verify that the AC lines are intact and haven't been spliced off by a previous owner, if everything looks OK I was going to replace the rear expansion valve and Orifice tube and recharge it from there. Any additional input would be great, thanks for the help.

so did you remove the rear passenger side kick panel and visually watch the actuator? or did you simply adjust the controls?
the rear ac lines will not be very cold at all one will be warm and one will be very slightly cool, they are the metal lines
best thing to do is to simply pull the panels off in the back and look at the actuator to see if it is really moving or not, the one closest to the blower motor is the one that controls hot/cold
the center portion has a hole and notch in it, the notch should move all the way forward/backward to the corresponding marks on the outer casing, see attached photo for reference

 

[91RS]

If you're front A/C is working then the rear A/C should as well because the lines are all connected to the same system and the refrigerant flows whether the rear HVAC is on or not. It is possible someone bypassed the rear system for whatever reason so make sure the lines are actually connected to something under the hood. They're not super common to leak in the south but they are really expensive to replace so I could see someone just buying two pickup truck A/C hoses and bypassing the rear A/C if they didn't want to fix it.

Either way, you more than likely have an actuator problem. I just replaced one in a friend's 14 he just bought. You can check for codes with a scan tool and command the actuators and see if they're doing what they're supposed to. If you have a short wheel base, the actuators will be on the inside of the case against the body so you will have to unbolt the case from the body and slightly roll it to get to the actuators (you don't have to disconnect the A/C or heater hoses to do this).