|Tech Article Title
|Keyless Entry Replacement ('96 A4)
Applies to the Keyless Entry system on a 1996 A4. (2 button remote)
Over the years, I have had lots of problems with the keyless entry system on my 1996 A4. The system seemed to either not work
or barely work most of the time. The system finally failed completely, and after checking the prices for replacement parts ($500 for
the receiver and $150 for the key fob), I decided to go a different route. I visited a local car stereo store (Car Toys in Boulder), and
purchased an aftermarket keyless entry system made by DEI, called the "Valet 710T" for $70. I also purchased two standard Bosch
SPDT relays for $5 each to control the turn signal flashing, since the new system wouldn't directly control the lights. The results are
pretty good. The range is much better than the old system (at least 50 feet), and there is an optional antenna I can add for even
better range if it ever gets to that. I also ended up with 2 key fobs and a new receiver for $70, less than 1/10 the cost of the Audi
The job is a bit easier than your average stereo installation, but be sure you are comfortable with car wiring before you start this.
This worked for me on my 1996 US model A4, but I can't promise it will work for you. I think some time in 1997 they changed the
system, so the wiring will be different for those cars.
The installation was fairly simple after I traced the wiring and figured out the functions. All the wiring can be done directly to the
harness that connected to the old receiver, and everything fits nicely under the rear seat cushion where the old system was. I was
able to do the job without modifying the car at all, and the work was completely reversible in case for any reason I wanted to put the
factory system back.
First, remove the rear seat lower cushion. To do this, just lift the front edge until it
unhooks from the frame, then slide it forward and remove it. You will find the old
receiver near the middle of the frame. It looks like the picture to the right.
Remove the old receiver with the mounting bracket. Disconnect the wiring connector.
You will notice that there is no connector for the thin coax antenna cable. To remove it,
you will either have to trace the cable back through the side bolster and up to the C
pillar where it ends, or cut the cable. (Don't cut the cable if you want to ever put the old
system back in.) Remove the mounting bracket from the receiver; this bracket works
pretty well to mount the new system after drilling a few holes.
Installation is straightforward. Start by finding a physical location for both relays and
the new receiver. I mounted the new receiver on the mounting bracket from the old
system, and mounted the relays using existing holes on the front lip of the seat base.
Make sure that all your installed parts will clear the seat when they are installed. Splice
the harness that comes with the new system into the old harness following the drawing
below. I chose to use "Scotchlok" connectors to splice into the harness without cutting
the old plug off. You could also cut the old plug off and wire the system directly; it's a
matter of personal preference.
You will notice several diodes in the installation. In several cases I was unsure of how the Audi system would react to the reverse
voltage that the Valet system provides on the lock wire when unlocking, and on the unlock wire when locking, so to be safe I added
diodes to block the reverse polarity signal. I have also tied the line from channel 3 of the Valet system (along with the lock line from
the Valet) to the lock wire of the Audi using a diode to isolate it. This allowed me to add the ability to close all the windows and
sunroof by holding button 2 on the remote, something that wasn't available on 1996 A4s. You should be able to use any
general-purpose diode that can handle over 20 volts and 1 amp. Be sure to observe the diode polarity.
Once you've made the connections, dress the wires using the existing wire trays. I wrapped the old connector and harness in a
piece of foam to keep it from rattling and protect it from contacting the metal chassis and shorting out.
The Valet needs to be programmed. Follow the instructions that came with it. Here is how I set mine up:
Key ON programming:
Use OEM Mode, (Button one set to Channel 1)
Add button 2 set to channel 3
Key on then off programming:
1. Active arming, ON
2. Honks Off (the Audi alarm takes care of this)
3. Auto lock OFF
4. Auto unlock OFF
5. Active locking ON
6. Ignition dome light control (OFF) the Audi alarm takes care of this)
7. 0.8 pulse duration ON (ignore what the book says, the system works better with short pulses)
8. Double pulse unlock ON (check the book, to turn this on, the LED will be off)
9. Security features (not used)
10. Code hopping ON
Once again, be sure that you have the skills to do this before you start the work. If not, I'm sure that the local stereo store will do
the work for a price, and it will still be cheaper than a new fob from Audi. I can't promise that what worked for me will work for you.
Link to the DEI website (replacement parts manufacturer)