How To - A/C Compressor Replacement and Refrigerant Recharge

[maschinenbauer]

This is a write-up on how to replace your air conditioning compressor in the event the clutch coil fails. The clutch coil takes in a signal from the computer to tell the compressor to turn on or not. When it's off, it acts as an idle pulley. You can see the hub is stationary while the pulley spins. When it's on, the hub and pulley spin together, now pumping refrigerant through the system and putting extra load on the engine. Our compressors are not meant to be serviceable, so you can't replace the clutch easily. If the actual compressor pump fails, it often puts metal chunks into the system which requires a flush. This does not include how to flush your A/C system, which is a much more involved process. This is only for the blown clutch coil, which requires replacement of a perfectly fine compressor pump

Total cost of special tools (gauges + tap + pump): $157 ($77 cheap pump)
Total cost of parts needed: $294.68
Total cost of repair: $451.68 ($371.68 cheap pump)

Dealer quote: $621.94 for the compressor, $965.07 including labor! And if they find any metal chunks in the line indicating pump (not coil) failure, it would be a whopping $1,431.28!!! Yikes, no thank you.

Diagnosis:

1. A/C system on, starts blowing warm air. You should not hear funny clunking sounds, which may indicate a bad compressor pump.
2. With A/C and engine on, visually inspect the hub of the compressor. If you see the hub stationary, the clutch is not engaged. Proceed to 3. If the hub is spinning with the belt, the clutch is engaged and you have a different problem. Probably a leak in the system or bad compressor pump.
   
3. Check the signal to the compressor. Unclip the electrical connector from the compressor. Hook up a voltmeter to the car-side of the connector. With the A/C and engine on, you should read 12V or -12V depending on how you hooked it up. If you get a voltage reading and the hub is not spinning, it is almost definitely a blown clutch coil. If you get no voltage reading, check for a blown fuse. If the fuses are intact, it is probably the pressure switch. The car will protect the compressor by not allowing it to click on when the refrigerant is too low.
   
4. Check the refrigerant pressure. This can be from the low-pressure port near the firewall on the passenger (timing belt) side of the engine bay. The proper way to check is with the compressor running, but we're just checking to see if there's pressure at all. Should be pretty high, around 100 psi without the compressor running. If there is no pressure, you have a different problem, most likely system leak.

Tools:

• E10, E16 Torx sockets (female) - for compressor removal
• T27 Torx socket (male) - for airbox removal (optional)
• 12-point 19mm socket - for accessory/serpentine belt removal. Cannot use 6-point hex socket!
• Socket extensions, u-joint
• Measuring cup or graduated cylinder - for filling compressor with oil
• A/C manifold gauges - about $50 at Harbor Freight, but try to opt for nicer ones because the HF ones are terrible.
• Pressure can tap - $7 at parts stores.
• Vacuum pump - must hold 29.99 in-hg for sustained time. Be cautious of the cheap $20 air-powered ones. You must have an industrial-sized air compressor for it to work, otherwise you won't pull the right pressure. Electric ones are preferred, which can cost about $100.
• Digital cooking scale - for measuring R134a added to system.

Parts and supplies:

• Air Conditioning Compressor - ACDelco 93168628, $264.84 shipped from Amazon
• A/C system seals and o-rings - GPD 1321260, $9.84 shipped from RockAuto.
• 0.45 kg of R134a refrigerant - $10 per 12oz (340 g) can at Walmart, two cans total. Avoid stuff with "leak sealer" because it can harm compressors.

*ignore the leak sealer refrigerant I originally bought. Ended up going back to the store for the normal stuff. Also not pictured: u-joint, cheater bar, scale.

Compressor replacement:
With engine off:

1. Discharge system (should still be fully charged if it's just the clutch coil). Try to find a shop that will scavenge it for free. Just call around. It's technically a federal offense to vent this stuff out yourself, and a big mess at that.
2. Take off accesory (serpentine) belt. Use a 12-point 19mm socket and a long hollow tube over the wrench to get a good mechanical advantage. There is a pin hole that can hold the tensioner open with a small allen key, but I didn't use it. You may have to remove the airbox, but you shouldn't have to.
3. Unplug the wire from the compressor. Remove small harness clip from the pressure line. The clip will stay with the harness.
4. Unbolt the pressure lines from the compressor (E10 socket + extensions + u-joint).
   
5. Unbolt the 3 mounting bolts (E16 socket) from the compressor and carefully remove the compressor. It helps to support the weight with one hand and use a socket wrench on the other. Lie on your back with legs pointing away from front of car and stick your head between the radiator and grill, plenty of room there for comfort and vision.
   
6. OIL BALANCING. These next steps are critical. Empty the old compressor's oil into a measuring cup. Hold it upside down, rotate the hub to pump it all out. Try to get every bit of oil out. Make a mark on the cup. Dispose of this oil. Note: if you find metal chunks in the oil, you have a compressor pump failure and need to flush the system.
   
   No metal bits!
7. On the new compressor, unbolt the plastic port cap (E10) and dispose of the oil that came with it. Try to get it all out again.
   
8. Pour in fresh PAG 46 oil, measured up to that same mark made earlier. Use the big hole. While pouring it in, slowly spin the compressor hub clockwise, but not too fast that it comes out the other hole.
   
9. Put the port cap back on and stand the compressor on its hub to let the oil spread to the rest of it, about 10 minutes.
   
10. Install the new compressor in reverse of step 5.
    
11. Take off old line seals and put new ones on the pressure line manifold.
    
12. Take off the port cap (E10) and bolt on the pressure line manifold with new seals installed.
13. Give the hub a good 10 spins or so.
14. Plug in the wire harness clip.
15. Put the accessory belt back on.

[maschinenbauer]

Evacuate and charge the system:
With engine off:

1. Hook up the low and high pressure lines to the manifold gauges (blue and red respectively). The red (high) is hard to get on, because the port is behind the grill. I detached the quick-release from the red line and threaded the line through some stuff behind the radiator, then screwed it back on.
   
   
   
   Looking up from under the grill
2. Open both pressure port valves. Open both gauge valves.
3. Hook up the vacuum pump to the yellow line and draw vacuum at 29.9 mm-hg for at least 30 minutes. At this vacuum level, water, old refrigerant, and contaminants will boil out of the system. The PAG will not boil out.
   
   This is when I first hooked it up. I let mine sit for about an hour, after which it was just on that 30 mark. A weak pump won't get more than 28 mm-hg.
4. After at least 30 minutes and with the vacuum still running, close the red and blue valves on the gauges. Then disconnect the vacuum pump. RED GAUGE VALVE STAYS CLOSED FROM NOW ON.
5. Wait 10 minutes or so to make sure the vacuum level does not drop. If it does, you have a leak and more work to do. Keep gauge valves closed.
6. Grab a can of refrigerant and screw the tap into place. Hook up the yellow hose to the can tap.
7. Tap the can by screwing the knob in and backing it out. You should hear the yellow line get filled.
8. Depress the pressure relief quickly with a screwdriver or something small. This forces air out of the line. You are now ready to charge.
   
9. Keeping the engine off and red gauge valve closed, open the blue valve while shaking the refrigerant can and alternating between sideways and vertical. Get the pressure to about atmospheric and then close the blue valve.
   
   With engine on:
10. Turn the A/C to max cold.
11. Using the same shaking method, open the blue valve again and empty the first can into the system. Should start blowing cool.
12. When the can is empty, close the blue valve. Close the tap and uncrew the old can. Screw a new can on and repeat the tapping and pressure relief procedure.
13. The required mass of R134a is 0.45 kg, as indicated on top of the grill. Put the full can on the cooking scale and zero it.
    
    I just subtracted 110 from 540, so I was shooting for 430. You can also see the tap hooked up to the yellow line here.
14. Open the blue valve and charge some of the new can while shaking. Every few seconds, close the valve and weigh the can. The first can put 340g into the system. We are shooting for 110g now for a total of 450g.
    
15. Once the full 450g has been charged, close the blue valve. You may now turn the engine off.
16. Close both pressure port valves and remove.
17. Safely and legally discharge the refrigerant from the manifold gauges and lines. Don't forget the dust caps on the ports!

[emg77]

Thanks for the great write-up and all the photos. I hope to never have to do this, but if I do, this seems like a great write-up.

[maschinenbauer]

Thanks, I hope it's helpful but at the same time I hope no one needs it. A/C is complicated and costly if not done right. I'm still not 100% sure I did every little thing right, but it seems to be playing nice after almost a week. If anyone has some tips/tricks/advice feel free to post them. User fdryer was very helpful in figuring out how to proceed with this repair.

[fdryer]

Please, don't drag me into this!? This is all your doing, and done well! You did everything possible for the best outcome and repair. Only time will tell whether a/c season continues or needed next year. It's always a gamble with a/c repairs; did I do it right and nothing leaks, will the next hard bump in the road cause another leak or will it last for as long as I drive my car? I'm in the same boat with a second repair I missed the first time. So far, my repairs lasted all summer and no new leaks any where.......... That's a good thing for me. Next year will tell me more as NYC weather cools off and I use less a/c.

[smwalker]

Is it worth taking the extra step to add some dye for future leak detection? Is that stuff available in small quantities? Like for one application as in this example?

[fdryer]

Dye was added during factory assembly and permanently mixed with oil. Unless oil is completely drained from a system, adding more dye isn't necessary. There are single dose dye packets for this purpose or refrigerant w/dye at higher cost than regular refrigerant. A simple look under the service valve caps will usually show dye to indicate how easily it leaks out. Dye remains in circulation and has no 'freshness date' - it doesn't fade away in a system. Once it leaks out, it will take a few weeks for dye to fade away. While fresh dye leaks are visible, a small uv blacklight is all that's needed to find dye stains anywhere it leaks outs, even weeks later.

[smwalker]

Originally Posted by fdryer

Dye was added during factory assembly and permanently mixed with oil. Unless oil is completely drained from a system, adding more dye isn't necessary. There are single dose dye packets for this purpose or refrigerant w/dye at higher cost than regular refrigerant. A simple look under the service valve caps will usually show dye to indicate how easily it leaks out. Dye remains in circulation and has no 'freshness date' - it doesn't fade away in a system. Once it leaks out, it will take a few weeks for dye to fade away. While fresh dye leaks are visible, a small uv blacklight is all that's needed to find dye stains anywhere it leaks outs, even weeks later.

Thanks FD good info. Then tell me this when is it advisable to add new dye? After a total system flush?

And is that statement a universal? Dye is added to oil on all factory systems of all manufactures?

[fdryer]

If a system requires a complete flush then oil, dye, and anything else is removed so dye replenishment would be a good idea. My 11yr old L300 still shows fresh dye glow when I removed a line and inadvertently tilted it, with oil and dye dribbling out on the garage floor. No uv light needed as the green dye is obvious. Glows bright with a uv light. Dye is an aid to searching for leaks, not a guarantee.

I use service manuals for information and Saturns use dye. I cannot comment on whether or not dye is used on Ferrari's, Range Rovers, Fords, Toyota's, etc.. In my opinion, its a no brainer to add (approximately) 1/4 ounce of dye to any vehicle a/c system at factory assembly to make it easier for most a/c techs to find a leak to reduce troubleshooting time. I'm not paid to work on a/c systems and it took all of 1 minute to point my inexpensive uv blacklight and find the source of my leak. In a typical parking lot at night just before going into Home Depot.

[phatfire6]

Wow, this is impressive

[smwalker]

maschinenbauer did you investigate just replacing your clutch and coil since your compressor was in good shape?

My coil also recently went out (Thermal Fuse Blew) and I see they have the coil and clutch available separately: 93180340 - About $250 so probably better off just getting the entire new compressor for not much more.

I went ahead and went the very cheap route and fixed (modified) my coil, removed a spacer in the clutch and put it back together. Should get a few more years out of the set up.

Once I did the evacuation (had a shop do it) I then took off the AC line and compressor to work on it out of the vehicle. Do not think you could do this stuff while it was still on the car.

What I found was my clutch was too far away from by pulley due to the clutch material wearing away over time. The gap was about as thick as a credit card. I would imagine the coil trying to overcome this gap got a bit hot and thus that was the reason for the thermal fuse to blow.

I removed the clutch with the single torx screw in the center and underneath the the clutch on the arbor of the compressor there was a single washer in there acting as a shim. I removed that and reinstalled the clutch and checked the clearance to the pulley. It still spun freely and the gap I had before was gone. So this will make it much easier for the coil to suck in the clutch to the pulley. The amount of clutch material that was left before it hits the rivets that hold it together was minimal. That's why I say I can probably only get a few more years out of the clutch set up.



So then I had to fix my coil. I removed the pulley to reveal the door that hid the thermal fuse behind it. You will need a pair of snap ring pliers ($3.50 from Harbor freight) to remove the ring that holds on the pulley then just a couple of flat head screw drivers to pry it off. It is not pressed on or anything just tight from years of sitting there. If you are in a corrosion state this might be impossible (get a new compressor)



Then I got to the thermal fuse. Pried out the two silver clips that hold it in and replaced it with about three strands of copper wire wound together. It is a bit of a risk not replacing the fuse with another fuse but I figure I will just diagnose ac problems the old fashioned way when the compressor stares screeching something is wrong. Thermal fuses on AC compressors are a rather new thing. Compressors before them just went till they failed. At least then you could feel good about replacing the compressor because you knew you needed one. Who knows how many compressors have been replaced needlessly because the thermal fuse blew because of a problem with the clutch. Makes the re-builders jobs much easier. I bet 3/4 of the compressor cores they get back are in perfect shape.



Then put it all back together with new o-rings ac the compressor fitting as maschinenbauer described below. Got it recharged and good to go.

Costs:
Evacuate AC system - Free
Draw down Vacuum test and Recharge AC system - $100.00 shop labor
No charge for freon since they took out just as much as they put in.
Snap Ring Pliers - $3.50 Harbor Freight
Compressor Fitting O-Rings - $5.00 - Local NAPA Auto Parts Store

[maschinenbauer]

Nice work! I did look into the thermal fuse replacement, but the compressor didn't cost much more so I went that route just in case.

I actually still have my old compressor lying around because I wanted to take it apart to see how to fix it... thanks for doing the thinkin work for me. I know space is tight under the engine, but I imagine this could maybe be done without breaking the lines open and having to recharge.

Clever thermal fuse replacement. I recall a similar fix to my clothes dryer in college... I wonder if the clutch material can be replaced. Do you have a picture of the clutch disc? 55k miles just seems so short for compressor life.

I have changed my driving habits to try to lengthen the life of my new A/C clutch. I only engage/disengage the A/C compressor while at idle so there is minimal friction and heat. Turning on the A/C at 85 mph on the freeway is probably like dumping the clutch at a drag race. Not good for wear

[Astra08]

Good info maschinenbauer and SM! That #93180340 is one pricey piece - looks like it's the $300 range now!

SM, what did you use to hold the clutch while removing the single Torx bolt? I use an impact wrench for jobs like this, but I know there's a special tool for use without it.

[maschinenbauer]

Geez, $300? That's more than what I spent on my whole compressor, shipped!

I bet you could hook up a 12V supply to the clutch coil harness to hold the pulley against the hub.

[smwalker]

Originally Posted by Astra08

Good info maschinenbauer and SM! That #93180340 is one pricey piece - looks like it's the $300 range now!

SM, what did you use to hold the clutch while removing the single Torx bolt? I use an impact wrench for jobs like this, but I know there's a special tool for use without it.

Yup the impact would be ideal. I just used the ol grip of death left hand method. Was not to tight. But mine was a non rust belt car so conditions may vary.

[smwalker]

Originally Posted by maschinenbauer

I know space is tight under the engine, but I imagine this could maybe be done without breaking the lines open and having to recharge.

I wonder if the clutch material can be replaced. Do you have a picture of the clutch disc? 55k miles just seems so short for compressor life.

As for doing it on the car, maybe through the wheel well, with the right snap ring pliers I think it could be done. May have to do some experimenting. The ring to get the coil off is significantly harder to remove than the one for the pulley. I would think you would want to at least take the coil out to do the tedious electrical work with that little thermal wire.

I did not get a pic of the face of the clutch, all I noted was that it was getting close to the rivets that hold it together. I have never seen a new one but I would imagine there is significantly more material there when new. Thus the reason for the gap the thickness of a credit card after 50k miles.

[fdryer]

Originally Posted by smwalker

......What I found was my clutch was too far away from by pulley due to the clutch material wearing away over time. The gap was about as thick as a credit card. I would imagine the coil trying to overcome this gap got a bit hot and thus that was the reason for the thermal fuse to blow.....
Then I got to the thermal fuse. Pried out the two silver clips that hold it in and replaced it with about three strands of copper wire wound together. It is a bit of a risk not replacing the fuse with another fuse but I figure I will just diagnose ac problems the old fashioned way when the compressor stares screeching something is wrong. Thermal fuses on AC compressors are a rather new thing. Compressors before them just went till they failed. At least then you could feel good about replacing the compressor because you knew you needed one. Who knows how many compressors have been replaced needlessly because the thermal fuse blew because of a problem with the clutch.......

From the service manual;

Important
Check reference gap between clutch and friction surface of the belt pulley at 4 points with feeler gauge and form mean value.

Adjust the reference gap for the compressor clutch.
Inspect reference gap of compressor clutch.
Specification
Reference value: 0.3-0.7 mm (0.012-0.028 in).

Correct the reference gap.

The air gap between clutch plate and pulley face allows complete disengagement when power is removed from the clutch coil. The clutch plate is designed for a certain amount of flex, acting as the mechanical equivalent of a hydraulic clutch without the complexity of a master/slave unit and oil. The minimum air gap prevents clutch plate slippage.

Thermal fuses serve a purpose, to open under certain conditions - typically 211-217°C (380-454°F). Overheating occurs if a system; a)is overfilled creating higher discharge pressures and temperatures causing compressors to work harder, heating up above expected operating temperatures, b)a break down occurring internal to a compressor possibly causing a seizure with the clutch plate slipping against the pulley face creating high enough temperatures from friction to heat up, detected by the thermal fuse to open and c)a dead short in the coil causing high current. Coils are around 2-3 ohms and can operate with around 7 amps - about 100watts, more current than high beams or HID lights. Thermal fuses provide another layer of protection for the a/c and electrical system and rarely fails. When they do open, its usually due to overheating situations.

The next time a/c is used, try feeling several places on the a/c system; the compressor body, discharge line from compressor to condenser coil and suction line return. Expect hot/very hot temps from the compressor and discharge line, cool to sweating suction line. Normal operating temperatures.

[smwalker]

God info, thanks fdryer. Wikipedia lists the thickness of a credit card at .76mm so I would imagine I was at the upper level of the acceptable margin. There was only one shim on the arbor so that is really the only adjustment I had.

I could feel the flex in the clutch plate but it did not seem anything could pull that down to the face of the pulley where it needed to be . Gap was just to big.

[Jerrycaterr]

Well thanks for the info but I call the experts, whenever i face such kind of problems!!!

[smwalker]

You are welcome Jerry and thanks for the entirely useless post.