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Discussion Starter · #1 ·
2008 TB. AC works, but hardly cold. The compressor clutch is engaged and good, and the gauge I purchased shows refrigerant level being good as well. The one thing I have noticed is that when the AC running (and the car is parked), there is excessive amount of moisture buildup around the accumulator. I mean, like water starts running under the car onto the ground like there is an open faucet under the car... i mean i can probably bottle the water and sell it !!!! I don't mind changing parts one by one (starting form the cheapest and easiest) until the issue is fixed, but correct me if I am wrong, there are no parts in the system that can be changed without having to capture the refrigerant first, correct? I am not willing to release refrigerant into the atmosphere, in which case I guess i have to go to a shop when i am suspecting min $800 . .thanks in advance for any suggestions.
 

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Well, from your description of the moisture buildup around the accumulator, it sounds like your system is operating normally. If you live in a humid area, there will be a ton of condensation near the accumulator. Now if you live in an area with low humidity there will be less condensation.

Without knowing the high and low side pressures, it is tough to properly diagnose what is going on. However, if the AC compressor is not cycling on and off, and the low side lines are cold, and the high side lines are warm to hot, then it sounds like the system is properly charged.

(and now for another) However, there is one thing that could be occurring that could cause you to have non-cold air coming out of the air ducts. One or more of the HVAC actuators that controls if you get hot air, warm air or cold air could have gone bad and is stuck in a position that is allowing the chilled air to mix with the heated air, and the result is not cold air coming out of the proper vents when you have the mode set to AC, and the temperature set to cold.

The number of actuators you have depends on the type of HVAC system you have - manual vs automatic.

I'm attaching an image of the HVAC assembly and where the HVAC actuators are. Now, I am not sure if the part numbers are valid for a 2008 model. I know they are valid for 2004 models and a year or two on either side.

Now if you wish to pursue this avenue there are several write ups in the "02 - 09 How-To and DIY Section of this forum.

Good Luck!
 

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Discussion Starter · #3 ·
Well, from your description of the moisture buildup around the accumulator, it sounds like your system is operating normally. If you live in a humid area, there will be a ton of condensation near the accumulator. Now if you live in an area with low humidity there will be less condensation.

Without knowing the high and low side pressures, it is tough to properly diagnose what is going on. However, if the AC compressor is not cycling on and off, and the low side lines are cold, and the high side lines are warm to hot, then it sounds like the system is properly charged.

(and now for another) However, there is one thing that could be occurring that could cause you to have non-cold air coming out of the air ducts. One or more of the HVAC actuators that controls if you get hot air, warm air or cold air could have gone bad and is stuck in a position that is allowing the chilled air to mix with the heated air, and the result is not cold air coming out of the proper vents when you have the mode set to AC, and the temperature set to cold.

The number of actuators you have depends on the type of HVAC system you have - manual vs automatic.

I'm attaching an image of the HVAC assembly and where the HVAC actuators are. Now, I am not sure if the part numbers are valid for a 2008 model. I know they are valid for 2004 models and a year or two on either side.

Now if you wish to pursue this avenue there are several write ups in the "02 - 09 How-To and DIY Section of this forum.

Good Luck!

Thank you. Yes, i just learned about the actuators and will be looking into that. But trust me when I say a lot of water dripping from under the car, I mean A LOT. Compared to any other car I have seen or currently have. The first time I notices it I thought it was coolant and my radiator had a hole in it. Anyway, I appreciate you replying back. I'll be looking into the actuator, sounds like a pain to get to them.
Is there a way to test the actuator once I get to it? Can they be manually adjusted to test?

P.s. My 2008 TB has only 40K miles on it.. although that may work against me since the system wasn't used often enough for the refrigerant/oil to keep the system lubricated (I think?!!!)
 

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You are welcome. By the way, both our 1992 Olds 88 and 1999 Silverado cause minor street flooding when the AC is on so you aren't alone.

No real way to test the actuators or manually move/adjust them without using the HVAC system itself.

What I would do is to start the TrailBlazer, turn the AC on and then see where the air comes out - defroster ducts, heater ducts, AC ducts, or some combination of the three. If the air does not come out where it should, then the HVAC Mode Actuator is bad and needs to be replaced. Next, move the driver's side temperature selector from cold to hot and see if the temperature changes. If it does change and the air temp goes from cold to hot, then the Driver's Side Temperature/Blend Door HVAC Actuator is good. Next, test the Passenger side Temperature setting to see if that Actuator is working right. Finally, with the mode selector in AC and the fan speed on 2 or 3, and the temperature selector set to cold, engage the AC Recirculation and you should be able to tell if the fan speeds up about a half unit (like going from the #2 fan speed to #2.5 fan speed) and the air temp coming out of the ducts is a bit colder. If you can hear/feel the difference, the Recirc Actuator is working fine.

Now, when you perform these tests, if you hear any thumping or creaking, that likely indicates one or more bad HVAC actuators. Note what you were changing when you hear the noise as that will indicate which actuator is bad/going bad.

Another thing you can do is to perform an HVAC system recalibration by removing the HVAC related fuses from the underhood electrical panel and the fuse panel located in the rear fuse block underneath the driver's side rear passenger seat for a couple of minutes. DO NOT remove the negative battery cable to perform this test. Also, this is somewhat of a risky thing to do because the actuators are aged and the plastic used in the gears is likely brittle, and one or more of the HVAC Actuators can be broken doing the recalibration procedure.

Here is the recalibration/relearn procedure should you desire to attempt it:

Remove the HVAC B fuse for a minimum of 10 seconds.
#36 in the rear fuse block.
Install the HVAC B fuse.
Place the ignition switch in the RUN position.
Wait 40 seconds for the auxiliary HVAC control module to self-calibrate.

If you are lucky, and none of the HVAC Actuators break, and none are broken, you might just get cold air back. If not, then you have one or more bad HVAC Actuators.

I hope this helps.
 
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