How-To Repair Your Air Conditioning

MRRSM

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This kind of repair involves more than just an R&R of a damaged compressor, since the old refrigerant must be removed from the system and stored in a proper container. Also... once the new compressor is installed, the system MUST have a near perfect vacuum established or the A/C will not ever cool properly. To avoid any woes (Whoas!) for your A/C repair, here are some suggestions for the fix that are "The Universal Baker's Dozen of Auto A/C Repair" :

1. Change the Accumulator at the same time the Compressor is swapped out. The reason is because the PAG oil that lubricates the system passes through the accumulator along with the return line refrigerant vapor and nested deep inside of the aluminum canister should be a packet of Silica Gel that acts as a hygroscopic sponge to absorb any traces of moisture/water vapor. As soon as you open any A/C system... ambient air loaded with water vapor will migrate not only into the Silica Gel pack,,, but the PAG oil will also sop or sponge up all the available moisture by literally yanking out of the exposed air. In short...any moisture not captured by a bone dry accumulator will freeze somewhere down in the lines and plug everything up with ice.

2. If you are NOT going to flush the A/C lines with the old compressor removed to flush out any residual dirt or metal particles from a FUBAR'd compressor... just cap all the lines as soon as you loosen and remove them to prevent the introduction of atmospheric air and non-condensable gases. Don't flush the A/C with the old compressor installed... all you will wind up doing is forcing more of any left over metal mung from inside the busted compressor deeper inside the liquid and vapor lines and have that crap lodge inside the evaporator coils and condensing coils units. Take the time and modest expense of flushing the lines of all this junk and the system will work better and get much cold(er).

3. Replace the pale green "O"Rings on all fittings with those of an exact thickness and diameter. If you use the ones that come from Autozone...there might be enough variation for them NOT to seal ...since they tend to be thinner and less "beefy" than the factory ones. You can use the old ones in a pinch as long as they show no signs from pressure erosion, wear or tearing. Just clean the interfaces between the hose piping fittings and lightly lube them with some fresh PAG oil. Be sure to recap your bottle of PAG oil...or it will be useless in twenty minutes from water saturation if left open to the air. Go light on the torque...these aluminum fittings and hosing are very touchy to accidental damage...its the "O"Rings that do the sealing... not excessive pressure on them from their fittings.

4. Before you install the new compressor... follow the manufacturer's recommended amount of PAG oil to be poured in. As a general rule of thumb... You should pour two (2) ounces inside the compressor and two (2) ounces inside the new accumulator...and sometimes it calls for two (2) more ounces to be poured inside the top of the condensing coil before the A/C Vapor Return Line is buttoned up at the top of the condenser coil.

5. *** It is very important to make sure you HAND TURN THE COMPRESSOR BEFORE INSTALLING THE PULLEY/SERPENTINE BELT(S) AT LEAST TEN (10) COMPLETE REVOLUTIONS, This will cycle the PAG Oil properly, correctly distribute the lubricant and prevent the compressor from hydro-locking. Then just install the Serpentine or V-Belt(s) and prepare to vacuum down the system. This is all done AFTER you attach the A/C hose manifold just after the compressor is bolted properly in place. A flashlight, mirror and 3/8" drive with long extensions will also help you down there, too.

6. It is worth it to head over to Harbor Freight and buy a 2.5 - 3 CFPM Vacuum Pump for around $150.00... If you own more than one car with A/C problems... fixing them yourself will surely recoup the $$$ with this item on hand. The important thing about the pump is that it be of the scroll design and be able to pull a double vacuum down to about 25 microns. It Is more important to use the most refined Vacuum Pump Oil that you can buy (about $7.00-$10.00 a quart and available via eBay) than it is to have a super-expensive unit like a Robinair or a Yellow Jacket Vacuum Pump pulling 6 CFPM). Harbor Freight also sells an inexpensive set of Auto Refrigerant Gauge Manifolds with all three pressure lines and High/Lo quick connectors, too.

7. After the proper vacuum period... anywhere from 30 minutes to a few hours depending upon how long and how open the system was prior to this repair... then its time to introduce the R-134A refrigerant into the clean and vacuumed system. This coolant should only be put into the system through the LOW SIDE (BLUE FITTING) LARGE CALIBER ALUMINUM LINE. NEVER install the gas from a can by just turning it upside down and allowing it into the LOW SIDE as a LIQUID! And likewise...NEVER allow either refrigerant vapor or liquid to be filled on the HIGH SIDE SMALLER CALIBER LIQUID LINE (RED FITTING). People have been killed when trying this and holding a can that exploded in their face because of excessive high pressures involved during compression. Only charge R-134A on the LOW SIDE fitting!

8. Don't be too macho about not wearing eye protection and heavy leather gloves while charging the system. If the lines or can should leak, burst or break and this super-cooled liquid splashes in your eyes or on your hands and arms...it will instantly freeze and permanently destroy those tissues. Be Careful With This Stuff!

9. After a proper vacuum of the system... With the engine OFF.... If you are not using your own A/C Manifold Gauge Set... Then use the type of service unit that comes with a built-in hand-squeeze control valve and its own Pressure Gauge to screw into the top of your various cans of R-134A and use the short hose Quick Connector valve and attach it to the LOW SIDE (BLUE) A/C Service Valve. Tighten down the connector. Then, start the engine at idle and turn on the A/C settings to HIGH COOL with the air blower set on HIGH. Slip an inexpensive analog A/C Thermometer inside one of the center vents to measure the temperature drop.

10. Don't be alarmed if the A/C compressor clutch does not instantly cycle on ...With the engine turned off, you will have to allow at least one can of R-134A to get inside the system and distribute itself for ten minutes or so. Then start the car and see if the LOW PRESSURE CUT OFF VALVE goes into detente and allows the compressor to engage with the electromagnetic clutch. With enough R-134A to get the pressure up, it will cycle on and off rapidly until there is enough coolant in the system to keep the clutch running continuously. As the Freon gas is going into the LOW SIDE LINE service valve... move the can from the 12:00 to 3:00 position and shake it gently to stimulate the liquid to vaporize sooner and enter the system. DON'T BE TEMPTED TO RUSH THIS PROCESS BY TURNING THE CAN UPSIDE DOWN... If you do this...you could "SLUG" the compressor and damage it badly since the COMPRESSOR IS DESIGNED TO COMPRESS VAPOR...AND ALL LIQUIDS ARE IN-COMPRESSIBLE!!!

11. Allow the system to normalize for three to five minutes after each injection of R-134A and prop the can/hose into the upright position if you are SOLO when checking the thermometer and feeling for changes in the interior of the car with all windows closed. AVOID PUTTING IN TOO MUCH REFRIGERANT! R-134A does not cool as efficiently as R-12 used to and Autozone sells a small yellow container of extra PAG Oil and a "Freeze Helper" that can make a big difference. This small can of stuff goes in EXACTLY like the regular cans of R-134A and at the very same LOW SIDE PORT (BLUE)

12. If you have to resort to using the small can of Special Sealer to stop any leaks that happen afterward, MAKE CERTAIN TO IMMEDIATELY PUT THE R-134A CHARGING HOSE RIGHT BACK ON AND PUMP SOME MORE FREON THROUGH THE SERVICE VALVE OR THE SEALER WILL PERMANENTLY PLUG UP THE SERVICE PORT!

13. KEEP YOUR COOL...and lay out your tools, parts and lubricants in an organized way and this job will be a BREEZE! Wash your hands and do NOT get any PAG OIL on your skin or in your eyes. This stuff is very irritating to them.... and with all that said....Best of Luck!
 
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MRRSM

MRRSM

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MRRSM

MRRSM

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Very soon now… some of us will encounter a situation involving unbearable discomfort and difficulty that will affect the quality of life for our families. Over the winter and spring months, ambient air that has been circulating endlessly through our Heat Pump and Air Conditioning Air Handlers has been passing likewise over and over through what are probably completely useless filters. Nested inside of the various air grills all around the house will be a myriad number of Air Filters of various shapes and sizes that have long since given up to the “Ghost of Neglect”... in part because they may be hidden behind furniture cabinets that have not been moved years! With the arrival of Summer, these filters are now completely clogged with Dirt, Pollen, Fungi, Mold and with the help of moisture have a mat of Gray Dirt seriously obstructing the AC Air Flow and become a battleground for pathogenic organisms yearning to break free and lodge themselves in the warm confines of our lungs... Such as the ones that can cause "Legionnaires Disease".

However, just beneath the skin of these Filters lies an even Bigger Problem. Because as the months have gone by and the “Change By Dates” have come and gone without observation, these Air Filters have long since failed to function. Meanwhile, everything that manages to slip by into the air stream of a particulate matter along with tiny organisms that are in the form of spores have completely coated the Evaporator Coils. This unhealthy stuff obstructs the flow of the ambient air passing over these cold coils where the original idea of losing the collected heat from the Air Stream has long since been defeated and keeps getting more and more clogged with dirt, acting as an insulator that can diminish the removal of "Latent Heat " and "Sensible Heat" from the obstructed Air Stream... thereby defeating its function and allowing warm, humid air to move through the air Ducts in the Home.

In the meantime...inside our homes, the “Lil' Women” are listening to the complaints of our uncomfortable kids... just now home from school for the summer and having the awful realization that even though the AC Thermostat was set to 72 Degrees… the actual Room Temperature reads 88 Degrees… which will explain why all the wives are sporting beads of sweat running down their collective temples. And to the last woman, they are cursing our names... because they feel helpless to a damned thing about it.

Her first inclination is to call for an Air Conditioning Technician to come by the house and do a Basic Service Call ($100 - $250) whose standing orders are to maximize each opportunity as profit for his company. And so these families will have to shell out the money necessary to do what even the most incompetent man on two legs can accomplish on his own if he simply does the following things:

(1) Make a “Body Count” of absolutely every In-Flow Air Duct Aluminum Grill panel and discover the dimensions of all the various air filters inside the house, noting this data on short Shopping List prior to visiting either Home Depot or Lowes for the necessary items. It will be important to purchase much Better Quality of Air Filters than you eventually pull out of these Air Boxes and none should ever be purchased if you can hold them up to the light and clearly see through them.

(2) If you are fortunate and live in a home or an apartment that has ground access to the Air Handler instead of the Attic, removing its access panel to the in-dwelling Evaporator “A” Frame Coils so that you can see first hand how much dirt and crap has been collecting forever on the front and backsides of the body of the coils... will be easy. The coils will be “Beer Can Cold” underneath that Dirt Blanket that has been obstructing them essentially forever. This is the tricky part… If there is enough Animal Hair collected around and on the coils and fins... carefully collect and immediately bag it up very gently. This action MUST be done without touching or squashing or bending the myriad Aluminum Fins on the Evaporator Coils.

(3) DO NOT EVER SCRUB OR TOUCH THE RAZOR SHARP ALUMINUM COILS!. They will easily collapse from the slightest impact and you won't know how badly cut you are until much later in the day when they start to get infected by all of the dirt in the wounds that gets picked up at the same time you get injured! WEAR RUBBER GLOVES!

(4) Home Depot and Lowes sell some very effective Hand Squeeze Spray Bottles of “NON_ACID Evaporator Coil Cleaner” that you will need to use to start spraying the coils from the Top Down...and from the Back to the Front in line with the Coil Fins… allowing the material to loosen and dissolve all that “Old HVAC MUNG” from the fins and coils and cascade downwards into the Plastic Condensate Collection Pan... and as long as the Drain in that Pan is NOT CLOGGED...the residual liquefied dirty solution will drain down from the Evaporator Coils and drain away outside of the house.

(5) IF THE OUTSIDE PVC GOOSE-NECK DRAIN IS PLUGGED UP… ALL THAT LIQUID MUNG WILL BACK UP INSIDE THE DRAIN PIPE AND SPILL OUT INTO THE AIR HANDLER CABINET OVER THE EDGES OF THE CONDENSATE PANS AND MAKE ONE HELLUVA MESS! You would be wise to observe where the PVC AC Condensate Drain Pipe it exits at the foundation of your house...and see whether or not it is flowing with a steady stream of water. If not, twist the Goose-neck Pipe loose and pull it completely off the wall pipe. Then tap it against a hard surface and you will see a Disgusting Phlegm Plug being discharged.

(6) If needs be… Take a Small Wet or Dry Shop Vacuum and fit the small hose nozzle over the mouth of the Wall PVC Pipe. Hold it tightly & Turn it On while listening to the Mung further up inside of the PCV Pipe leading from the clogged Condensate Drain Pan underneath the Evaporator Coils as the plugs break loose and get sucked down into the Vacuum Hopper. Dump this crap in the toilet and flush the hopper outside with some Bleach and then flush it clean with a garden hose....do the same thing to the Vacuum Hose!

(7) Re-Install the Air Handler Panel...Air Tight! Use Aluminized HVAC Tape on the seams if you can hear any air escaping from within!

(8) If you open the panel and find the Evaporator or Outside Condenser FROZEN OVER ...there is no doubt about the cause being a LOW REFRIGERANT CHARGE. Do NOT be tempted to prop up the system by injecting R-22A or straight Propane Fuel into the system as these are Highly Flammable Gases that might ignite near any Leaking Copper HVAC Tubing ...and START A FIRE THAT WINDS UP BURNING YOUR HOUSE DOWN! At this point... calling a Qualified Service Technician to sort this problem out will be a MUST!


If you do all of these things...The Home Temperature will Drop like a Stone... along with your Electric Bill...The Air Velocity will Increase...The Air itself will be much Cleaner and More Breathable. And so, when the “Lil' Women” and the Kids are happy... WE are happy!

I like this First Video for its Instructional Value… BUT I DO NOT ADVOCATE USING ANY BRUSH ON THE EVAPORATOR COILS... EVER!
YOU DO NOT NEED TO DO THIS ACTION OF REMOVING YOUR EVAPORATOR COIL THEY WAY THIS MAN DID! You can just clean the coils inside your Air Handler in place! This next video gives a better overall view of the Evaporator "A" Frame Coil Design... but the problem with what the OP did was that he did FAILED TO BRAZE ON END CAPS TO HIS HIGH AND LOW REFRIGERANT LINES... and then pressurize the coil interior with around 100 PSI of Dry Nitrogen before doing all of this Dramatic High Pressure Cleaning... THIS IS A BIG MISTAKE!
 
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pell

Active Member
So having getting the blower going the A/C still not working. Just looking online as what I need to do replacement of compressor and other parts. Waiting on port adapters for my gauge set to check high pressure. But it seems"with rear air " comes up a lot in parts search. Out of the console in the rear seat area there is a power button there with vents does this mean rear air?
 
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MRRSM

MRRSM

Lifetime VIP Supporter
Since you are already an Experienced HVAC Technician... You have a decided advantage over most people with A/C problems..Now you just need to get your hands on the GM OEM Service Manual and research it for the Trailblazers and Envoys with Dual A/C Systems. You can find and Download what you need by visiting @Mooseman 's Thread, "Need Service Manuals? Get them HERE" linked below:

 

Mooseman

Moderator
Just to clarify, you have rear HVAC if it is an EXT/XL truck. Otherwise, it is a single system despite the rear vent and controls. This is important for the amount of refrigerant and for troubleshooting leaks.
 
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sunliner

Well-Known Member
is the clutch on the compressor removable by a DIY-level owner? mine has made a God-awful racket for the last few years, only when turned on so I *think* it's the clutch....still cools the inside of the truck pretty darn good, even in a Florida summer so I'm hoping to avoid replacing the whole deal
 

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