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Air Conditioning Evaporator Core Replacement
evaporator part number: 8D1-820-103-D

below are general instructions for getting into the HVAC box behind the dash to replace the AC evaporator core. The same instructions can be used to get at the heater core. Note I'm doing this writeup well after i performed the procedure so it won't be as step by step as some. Still, while this is a long job, it is not that intimidating. It took us (2-3 people) about a day and a bit to complete this job.

First you'll have to get the system discharged. A discharge and recharge (the latter after you're done the job) will run you just north of $100.

8?mm, 10mm, 13mm sockets
small torx bits
T55 torx bit
phillips and flat head screwdriver
8mm allen wrench
flex shaft (very handy, but you might get away without one)

r134-a refrigerant oil

First disconnect the battery. You'll be taking apart the entire dash, so there's plenty of stuff you'll be messing with you'd rather not have powered (airbags, anyone?).

First off remove the steering wheel, driver's side lower dash, gauge pod, glove box, and center console. From there remove anything that's securing the dash. Gentle pulling will reveal where it's still attached. Once you've got all the screws/bolts removed, the dash will slide straight away from the windshield and then you can take it out of the car. Careful to disconnect all the electircal plugs as you disassemble things.

Next, disconnect the coolant and ac lines (in the engine bay). Make sure the engine has been off long enough for the majority of the coolant to drain from the lines. I opened the cap of the overflow resivoir just to make sure there was no pressure left in the system.

Back the hoses off the connectors at the wall next to the battery. It's easier if you unbolt the battery restraint on the other end of the battery, so you have some room to maneuver. you'll likely spill a little bit of coolant no matter what you do.

The bolt on the AC line is an 8mm allen wrench.

Once the lines are disconnected, you can maneuver the hvac box out of the car. It's a tight fit, and probably will need some coaxing (read: yanking) to get it out. Try not to spill any coolant from the heater core, which is in the HVAC box and is still full. Basically, this means not tilting the box during extraction. If you're cleverer than i was, you could probably use a fluid extractor from the engine bay side to rid the core of some of the excess coolant first.

The housing:

The top and bottom halves of the box are held together by a dozen or more silver clips. There's also a mechanical mechanism on the back of the box that needs partially disassembling. I also took out the heater core before opening the box (a couple of screws and it slides out of the top).

Now for the easy part. slip the old core out, and the new core in:

Now reverse everything you did and hopefully you won't have too many screws left over. Replace the o-rings on the pipes leading to the evaporator from the engine bay, lubricating them with the refrigerant oil. Make sure that when you screw the bolt for those pipes back in that they are properly aligned, or you may damage the o-rings like i did my first try.

  • Take pictures as you go. It may help you remember how certain pieces behind the dash are oriented (some of the metal plates).
  • Keep the fasteners organized! I didn't and wound up with leftovers. If you've already got a good method for this, great. Otherwise I'd suggest taping the fasteners to the parts they belong to (with some strong tape).
  • Check that the mechanic tests for the system's ability to hold pressure before they recharge the system. In case something went awry, you won't have to go through the evac and recharge system all over again. The mechanic I used checked to make sure it held vacuum for 1/2 hour before he recharged it.
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