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Pulling Rear AC out of 89 S4

 
Old 01-31-2019, 02:49 AM
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dsafian
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Default Pulling Rear AC out of 89 S4

Hi, I'm new to the forum, just picked up and 89 S4, my first, and found that there was some water intrusion after a rainstorm - sunroof car. I've pulled out the rear seats and carpeting, and would like to
remove all the foam and cracked rubber to replace it with sound proofing and some closed cell foam. I'd like remove the rear center AC unit so that that I can do a clean install and have been searching around for some info on how to best remove the unit without damaging anything. Any info / pics would be most appreciated!
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Old 01-31-2019, 03:11 AM
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Welcome to Rennlist!

I strongly recommend that you grab a CD copy of the workshop manual set so you can see how all that plays together. Disassembly starts with the grills and the cover, draining and disconnecting the refrigeration system, then the electrical side. The evaporator will come out then, giving the access you are looking for with the clean-out and sound deadening. If you just want to remove the cover, start by gently lifting the grill vents out, and the cover removal will be obvious.
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Old 01-31-2019, 03:24 AM
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Originally Posted by dr bob View Post
Welcome to Rennlist!

I strongly recommend that you grab a CD copy of the workshop manual set so you can see how all that plays together. Disassembly starts with the grills and the cover, draining and disconnecting the refrigeration system, then the electrical side. The evaporator will come out then, giving the access you are looking for with the clean-out and sound deadening. If you just want to remove the cover, start by gently lifting the grill vents out, and the cover removal will be obvious.
Thanks Bob. I figured out the vents / covers - but didn't want to mess with the refrigerant and the rest till I got a little more info. I'll look into a workshop manual - makes sense.
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Old 01-31-2019, 06:48 AM
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To get you started there's this link..

http://www.ligeti.com/928/

however the CD set from one of the 928 forum vendors includes a bunch of extra technical bulletins, spec books etc. so is worth getting as you go deeper.
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Old 01-31-2019, 01:16 PM
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I just did this, it is not too bad to remove but yes you are going to need to evacuate the refrigerant and at that point you might as well replace all the seals in the rear of the system at the very least ... I would be tempted to do the whole system. Roger at 928sRus sells seal kits for the front and back.

At a pinch you could just unbolt the rear lines at the expansion valve and then there is an electrical connector right behind the lines to disconnect, at that point there are 4 or 5 screws on the side of the AC unit and it will lift free. There are another 4 screws and you can pull the brackets and spacers that support the AC unit.

I would be tempted to go further and remove the lines from the floor under the passenger seat to give access to the rest of the o-rings and then you can get the rear hoses rebuilt but that is your call. Depends how far you want to go.

I replaced the rear foam with Dynamat Extreme, see below.

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Old 01-31-2019, 03:56 PM
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I quite literally did most of this job 48 hours ago and have done the full job before.

As has been pointed out you will have to discharge your A/C.
As Chris shows in his picture, you won't really be able to get new material under the rear A/C system unless you remove it.
Removing the mechanical bits of the rear A/C is easy:
Three fasteners for the expansion valve. Once the valve is out ...
a couple of screws for the evaporator
a couple of bolts for the blower and evaporator housing.
The harness for the rear A/C has a multi-pin connector next to the seat belt latch; you don't even need to unplug the relay next to the blower.
Then there are two brackets and four big screws for these housing brackets. Four spacers under the brackets.

Now, the hoses...
the hoses aren't as strong as the glue that glues them to the carpet. And under the p-side seat the low pressure hose is integral with the floorboard fitting to the hard lines under the car.
To remove the interior hoses you will need to:
- remove the two ~3 foot lines under the car
- unscrew the floorboard fitting retainer ring under the car
- disconnect the interior hoses from the fitting and refrigerant valve and remove the valve
At that point, unless you want to do an "accidental rear A/C delete" you'll want to very carefully
- loosen the floorboard fitting
- work the hoses free from their glue
Do not bend, even slightly, the 'hard line' part of the hoses.
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Old 01-31-2019, 09:05 PM
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I still dont see why 70lbs of dynomat in a car counts as "proofing".

But..thats another thread. And a whole industry raking in the $$ selling butyl and tinfoil.
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Old 02-01-2019, 04:10 AM
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Dynamat, B-quiet, etc. all prevent sound from being generated. Think putting your hand on a cymbal. It lowers a panels resonant frequency by adding mass.

Foam absorbs sound, which is why it is in our cars above the rear tires and under the seats and floor mats.

Put foam or proper automotive insulation like 3M Thinsulate anywhere you can that can resonate, like the holes behind the 6 in speakers in the quarter panel.

Just don't fill that area with anything that can prevent air flow, like closed cell foam or expanding foam from a can. Those holes are what vent the cabin.
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Old 02-02-2019, 02:50 AM
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Originally Posted by Chris View Post
I just did this, it is not too bad to remove but yes you are going to need to evacuate the refrigerant and at that point you might as well replace all the seals in the rear of the system at the very least ... I would be tempted to do the whole system. Roger at 928sRus sells seal kits for the front and back.

At a pinch you could just unbolt the rear lines at the expansion valve and then there is an electrical connector right behind the lines to disconnect, at that point there are 4 or 5 screws on the side of the AC unit and it will lift free. There are another 4 screws and you can pull the brackets and spacers that support the AC unit.

I would be tempted to go further and remove the lines from the floor under the passenger seat to give access to the rest of the o-rings and then you can get the rear hoses rebuilt but that is your call. Depends how far you want to go.

I replaced the rear foam with Dynamat Extreme, see below.

Yeah, this is where I'm headed. I'm not sure if I want to re-do the whole system, but definitely want to get the foam out from under it replaced. I was looking at the Dynamat, as well as, some other products. I saw another post where they did the sound mat and 1/2" closed-cell foam - which is kinda where I was thinking about going. Still pondering - Thanks!
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Old 02-02-2019, 02:53 AM
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Originally Posted by worf928 View Post
I quite literally did most of this job 48 hours ago and have done the full job before.

As has been pointed out you will have to discharge your A/C.
As Chris shows in his picture, you won't really be able to get new material under the rear A/C system unless you remove it.
Removing the mechanical bits of the rear A/C is easy:
Three fasteners for the expansion valve. Once the valve is out ...
a couple of screws for the evaporator
a couple of bolts for the blower and evaporator housing.
The harness for the rear A/C has a multi-pin connector next to the seat belt latch; you don't even need to unplug the relay next to the blower.
Then there are two brackets and four big screws for these housing brackets. Four spacers under the brackets.

Now, the hoses...
the hoses aren't as strong as the glue that glues them to the carpet. And under the p-side seat the low pressure hose is integral with the floorboard fitting to the hard lines under the car.
To remove the interior hoses you will need to:
- remove the two ~3 foot lines under the car
- unscrew the floorboard fitting retainer ring under the car
- disconnect the interior hoses from the fitting and refrigerant valve and remove the valve
At that point, unless you want to do an "accidental rear A/C delete" you'll want to very carefully
- loosen the floorboard fitting
- work the hoses free from their glue
Do not bend, even slightly, the 'hard line' part of the hoses.
Sigh. This would be the right way to do this for sure. Def do not want an 'accidental' delete.
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Old 02-02-2019, 02:54 AM
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Gracias!
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Old 02-02-2019, 02:57 AM
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Thanks for that.
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Old 02-02-2019, 02:58 AM
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Originally Posted by The Forgotten On View Post
Dynamat, B-quiet, etc. all prevent sound from being generated. Think putting your hand on a cymbal. It lowers a panels resonant frequency by adding mass.

Foam absorbs sound, which is why it is in our cars above the rear tires and under the seats and floor mats.

Put foam or proper automotive insulation like 3M Thinsulate anywhere you can that can resonate, like the holes behind the 6 in speakers in the quarter panel.

Just don't fill that area with anything that can prevent air flow, like closed cell foam or expanding foam from a can. Those holes are what vent the cabin.
thanks for that
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