Automatic ac system 2002 Trailblazer


Old 07-25-09, 05:18 PM
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Join Date: Jul 2009
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Automatic ac system 2002 Trailblazer

Hello I have a 2002 Chevy Trailblazer (rear ac) with CJ2 HVAC automatic air conditioning. Originally compressor will not cycle properly. High pressure would continue to grow until compressor cycled (disengaged) and low side would grow as well. I thought the compressor was bad I flushed the system and replaced orifice, compressor and filter dryer. That wasn't the problem. I've done countless ac systems but never an automatic system, is there something different in the procrdures. Chilton tells you that its above the home mechanic.
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Old 07-25-09, 07:36 PM
Unclediezel's Avatar
Join Date: Dec 2006
Location: Northeastern PA.
Posts: 2,230
Chilton has it right......

I have personally witnessed 3 separate instances where a "Do it yourself and save $" kit went horribly wrong.....Cold air in your vehicle doesnt matter if your blind and frostbitten to the point of disfigurement..

Now... Having said that , I will give you an opinion , Strictly for the purpose of making an Informed decision when you take it to the Mechanic......

One or both of your expansion devices (Either orifice tube or expansion valve for the rear) have failed, the condenser is restricted, or ....(I hope the system was evacuated after the flush) it is overcharged.....Which will be much more pronounced if you filled the system without removing the air/ flushing solvent. If you can "Pressurize the system beyond "HI-CUTOFF" limits...I would seriously doubt the compressor is at fault, But exactly the opposite...He is capable of doing his Job....

BUT....Prolonged operation at or near Hi pressure limits, WILL make short work of TRASHING a functional compressor.
Old 07-26-09, 04:39 AM
Join Date: Apr 2006
Location: Floriduhhhhh Us of A
Posts: 611
Gotta disagree Unc............If he had a restriction, as the high side climbed the low side would drop out...........BOTH sides climbing indicate either an overcharged system or a radiator fan not dispersing the heat........(or trash in front of the rad)

But I DO agree that A/C is not really a DIY kinda job safety wise
Old 07-26-09, 08:45 AM
Unclediezel's Avatar
Join Date: Dec 2006
Location: Northeastern PA.
Posts: 2,230

Sorry, I mis read that. I assumed the low pressure Climbed when the compressor disengaged..

Absolutely correct Wrench....Hi "Pressure" AND Hi "Suction" would Typically indicate lack of airflow or an "Inability" of the condenser to dissipate heat. Since Pressure and heat coincide , The extra heat turns to extra Pressure on Both Ends.....

A quick word about Charging......More is definitely NOT better, and can actually be much worse.....It is better to be 1/2 pound short, than 3 ounces over....Which is where the safety issue comes in, and without the "Shop Environment" or the necessary equipment...A "Guess" on a correct A/C charge can prove expensive at best, and can quickly turn to HAZARDOUS....

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