HVAC Disassembly and Cleaning

The design of the cup holder on the 1999½ Audi A4 (and other years/models) has a rather problematic side effect. If and when (and it will happen) a drink spills, it drips all over your radio and HVAC causing the keys to being sluggish and sometimes stick. While in +20°C weather the key will probably return fairly quickly, at -35°C your lucky if the key returns at all.

Something needed to be done:

• No more drinks that spill (or even better, no drinks in the car at all)
• Educate your favorite drive-thru restaurant on how to properly serve drinks
• Fix the sticky keys

This procedure will deal with the HVAC unit itself. The radio (Concert) is much easier to disassemble and won't be covered here.

Dealer replacement value of the unit (8D0 820 043N B98) is over 800 $CDN (500 $US). Treat it with care. You've got better things to spend that money on if you happen to damage it. That being said, I take no responsibility of your actions in removing and opening your unit. These were the steps I did in order to back out of Audi's design oversight. My vehicle is still under warranty, I probably should have got it replaced at Audi's expense. However, I don't feel to comfortable with my dealer ripping apart my center console.

Your unit may differ, but I suspect the same technique will still apply.

UNIT REMOVAL HINTS

Here is the center console with the radio and HVAC unit removed. How you get to this step will probably be the most unprofessional work you'll ever perform on your car. I have no idea what Audi was thinking when they decided on the mounting method for the unit (or I'm missing something here?).

The radio was a breeze. Make sure you know it's unique security code before removing it. The difficult part is getting the proper key removal tools. If your Audi/VW dealer is reasonable, they may be willing to release the radio for you if you take a visit to them. Once you've got the radio released from it's mounting clips, it's a simple matter of pulling it out.

The HVAC unit is held in place with FOUR angle brackets that clip into place when it was initially installed at the factory. These are troublesome to release. The top pair are easy to release with a small screwdriver. You can pull them slightly forward from their normal position so they no longer catch the surrounding plastic. The bottom clips are about the same distance apart, but are quite a bit further back along the bottom side. I wasn't able to see them from the outside. I had to jamb two thick screwdrivers under the unit distorting the plastic brace above the ash tray. The idea was to push the brace away from the clips so you could pull the unit out without them catching.

In stead of pulling, I found that putting your hand inside the radio opening and pushing the unit out was easier. It's your choice, but there isn't much of a grip on the front of the unit for you to pull on.

During your extraction, be careful not to damage the bottom rubber bushings as you deal with the bottom retainer-clips. These are for shock suppression and probably reduce the rattling of  assemblies..

This is the dreaded bottom retainer-clip that holds the bottom of the unit in. Due to the difficulty in removing the unit with these clips installed, I have removed them before re-installing. This will make removal MUCH easier should you need to remove it again in the future. I have no idea as to what impact this will have on holding the unit flush with the center instrument trim.  Everything seems fine at the moment.

TOOLS

Nothing really special except for a really-really small Torx screwdriver.  My Torx set didn't go small enough. I found that one of my jeweler's flathead screwdriver's fit just in side the Torx head without slipping.

DISPLAY-HEAD SEPARATION

Here's the unit removed from the center console.

Set the unit face down on some soft clean surface being careful not to scratch the face. You'll need to remove the FOUR screws on the backside of the assembly (Torx head). These are relatively short and easy to remove.

You may choose to remove the temperature blower (Torx head), but on this style of unit it wasn't necessary. Your unit may differ.  I removed the TWO screws and pulled up.  The contacts for the motor just slide out like a connector.

At this point, the display-head will be lose, but still inseparable. There are TWO hooks on the top, near where the temperature blower is that need to be slightly depressed.

Slip the end of the jeweler's screwdriver tip between the display-head and the unit-body. Gently lift the unit-body plastic up over the display-head. Go easy! If you look closely, you can see dents from my initial attempts. You'll now have the display-head section separated from the unit-body by way of a ribbon cable. ESD precautions.

You now have exposed a good portion of the unit electronics.  This is static sensitive device.  Handle as little of the electronic components as possible.  Don't be walking around your house with the unit open to show all your friends how cool it looks inside.  Even the tiniest of electrostatic discharge can destroy the unit.  If you live in a low humidity area, you might also want to think about grounding your self.

Carefully place the display-head face down. Remove the FIVE screws that hold the faceplate to the display board.

Set aside the electronics portion for later reassembly.  You might want to make sure the LCD display is clean.  Don't use any chemicals that may damage the glass.

KEY REMOVAL

Place the keypad assembly face down. You'll notice that the keys get some of their bounce from the metal frame that floats around the backside of the keys. One must be careful not to stress and damage the frame when removing keys.

Locate the slider-holes for each of the keys that you wish to remove. Each key has at least TWO holes that guide the key. The holes also function to limit the keys travel (to retain the key in the cavity). In the factory, these keys are pushed in from the front past the point of the interference inside the slider-holes. You're going to have to reverse that process in order to remove the key. It's not easy! The assembly wasn't designed with key removal in mind.

To remove a key, you need to push the key past it's interference point. Do one side of the key, then the other. Great care must be taken NOT to damage the cavity glide paths and key latches or the key will no longer travel smoothly or 'pops- out' when you take your finger off. TAKE YOUR TIME!. If a key isn't releasing, find out why. It takes a bit of pressure, but not a whole lot. After 2 or 3 keys, you should get a good feel as a technique.

The two rocker keys (TEMPERATURE & FAN SPEED) can be easily removed by pressing down simultaneously on the studs located on the back of the key. (The studs are the plastic portion that are in contact the switches on the display board).

Once again, be careful not to damage the guides. Here you can see some minor damage I had. You should clean out any plastic bits that were created when the key popped out. Don't get too carried away or you'll risk the key not holding when you reassembly everything.

CLEANING

Now you have all the necessary keys removed from their respective cavities (take note before you start as to which keys are sticky!). Examine each key and cavity for the source of the problem. Dirt and fluid reside are prime candidates.

Notice the shinny "goop". This is causing the keys to stick to the keypad assembly. Yours may look different, but this is what Coke leaves behind on my keys.

Clean the keys with a suitable cleaner. I used Simple Green.  Don't use anything too strong (like rubbing alcohol), or you'll damage the plastic. I also washed the parts under warm soapy water to remove any residue. Make sure all the parts are free of water or rust will develop on the metal spring frame.

REASSEMBLY

Reassembly is just the reversal of the above steps. Take your time, double check to put the keys back in the correct cavities. Make sure you're orienting the keys correctly (e.g.. No up-side-down TEMPERATURE or FAN SPEED keys!). Double check that each key sits smartly into each cavity without binding. If the key tends to pop out, you may have damaged the cavity guides or hooks during the removal process. I didn't run into this, but you can try fiddling with the plastic guides or hooks to bring them out a little so there is a interference fit.

When your all done, sit back and admire the crisp clean "click" when you press the buttons.

Good luck!

Last updated: 2002/08/08 21:11