AC Compressor Replacement

  • 2.4L
  • 4 CYL
  • AWD
  • 125,000 MILES
2007 Toyota Highlander with 2.4L engine. AC Compressor shot. Mechanic wants $900 to do complete job. Sounds about right, but I dont have the scratch. I am fairly mechanical. I know there are "tricks to the trade" with replacing AC compressors. Would anyone be able to provide "detailed" instructions or reference a "detailed" video on how to replace the compressor, crossing all the "T's and dotting all of the "I"'s? Thank you.
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Thursday, May 21st, 2015 AT 9:59 AM

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You're asking for something we can't deliver. For big jobs like this you need a copy of the manufacturer's service manual. There would be way too much to retype. My fingerprints would be worn off! The next problem is this is a very basic job for a professional, and as such, how to replace the compressor would be covered, but not the entire job. Another similar job would be mounting and balancing a set of new tires. That is covered in a mechanic's basic training. It too is not covered in service manuals.

The next problem is this is definitely not a do-it-yourself project. The first thing you have to do is remove, recover, and recycle the refrigerant. That requires very expensive equipment, the operator must have a federal license, and the shop must be licensed.

You might be able to replace the compressor yourself once the refrigerant has been removed, but then the system has to be sucked into a vacuum for at least half an hour. Longer is better. Moisture from humidity in the air gets into the system while the hoses are removed from the compressor. If that isn't removed, droplets will circulate with the refrigerant, and they'll freeze and block flow at the port where the compressed refrigerant expands and gets real cold. You'll get warm air for up to 20 minutes until that droplet melts. Also, moisture mixed with refrigerant forms an acid that attacks metal parts. What you think you're saving on labor costs you'll spend many times over replacing leaking condensers and evaporators. When under vacuum, water boils at 77 degrees F. And vaporizes so it can be sucked out.

Once the system has been under vacuum, the mechanic will watch the gauges to see if it stays that way. If the vacuum is lost rather quickly, it's because there's a leak that must be addressed. If it loses vacuum slowly, it could mean there's still water in the system that's still expanding. The system needs to be put under vacuum for a longer period of time for that.

Once the system holds vacuum long enough to show it's ready to receive the new charge, the refrigerant will be sucked in by that vacuum. You can buy cans of R-134, but the vacuum will be lost when you disconnect the hose to the vacuum pump. That brings new moisture into the system. To avoid this you need a charging station that has the vacuum pump built in. You don't have one of those and you can't rent one. Even if you had the machine, which is expensive, no one will sell you a tank of refrigerant unless you show them your license or have it on file.

The charging stations get programmed to pump in the correct amount of refrigerant, by weight. You can't tell by looking at the gauges how much you've put in. Compressors can only pump a vapor which can be compressed. If the system is significantly over-charged, liquid can slosh into the compressor and damage it. Also, over-charging it means there's too much liquid refrigerant in the evaporator in the dash. It will boil and turn into a vapor too late, meaning under the hood where it's on its way back to the compressor. Where it turns into a vapor is where it gets real cold. You want that to take place in the dash where the air is blowing through, not under the hood where it won't do you any good.

When any part is replaced, there is a specified amount of oil that must be added. That oil circulates with the refrigerant so the two fluids must be compatible. There is a plug on the compressor to remove, then the correct amount of oil is added there, or you pour it into one of the hose connections. You have to buy a container of oil, and you'll be paying for a lot more than you need.

The most important detail is refrigerant is extremely dangerous to work with. It can cause frostbite and blindness. At a minimum a professional will wear safety glasses and gloves, and experienced specialists also wear a face shield.

The best you can hope for, if you have a willing mechanic and shop owner, is they will suck out the refrigerant, then send you home to do your compressor replacement, then you bring it back to have the system evacuated and charged. The problem is while they will check your work, they will not be responsible if there's a leak. That sounds unlikely but you'd be surprised at how often we have to install a hose a second time to get it right. By law, no one can legally add refrigerant or charge a system with a leak, and no mechanic will risk his reputation by doing that or risk getting his boss in trouble. That means if they find a leak, you'll be charged for checking the system, which involves adding refrigerant, so you'll be charged for the refrigerant too, and for recovering it again. Then you get to go back home, do the work again, and bring it back again. At this point your cost savings has gone out the window.

Some shop owners don't allow their employees to do parts of the job just for this reason. They know too well that the chance of saving a customer a few dollars by letting them do part of the job them self has a low chance of success, and there's a real good chance the car owner is going to end up unhappy and blame the mechanic or the shop. This would be similar to having tests done by one doctor, then taking the charts to a different doctor for a diagnosis, then to yet a different one for treatment. You know the total cost will be higher than if you let one doctor do everything.

$900.00 seems a little high so you might want to get a second estimate from another shop. It depends though on how hard the compressor is to replace. Some vehicles are designed to get them off the assembly line in a hurry with no regard to future serviceability. Replacing a compressor can take an hour on one model and half a day on another one. You might also want to ask at a radiator repair shop or air conditioning specialty shop. Naturally anyone who specializes in one area such as this is going to be faster and more efficient. They are also more likely to have anything they unexpectedly need in stock, like special gaskets and seals.

If I still haven't convinced you to avoid these potential headaches, go to a nearby community college with an Automotive program. They'll have copies of recent textbooks in their libraries that you can look through. Read through the chapters on recharging the system, then see if you still think it's a good value to take this on. Note too that in my school, we had an 8-week class, 22 hours per week, just for heating and air conditioning. The kids were halfway through their training before they even got to replacing parts and charging the systems. You're wanting to bypass all that training and jump right to replacing parts. You have to know you'll be missing something. That's where reading the textbook could be enlightening.
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Thursday, May 21st, 2015 AT 4:24 PM

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