[s-cars] 94 S4 infra-red key replacement options

Theodore Chen tedebearp at yahoo.com
Wed Mar 18 12:22:27 PDT 2009

here are a couple of links that might help:



there used to be a wiring diagram at the audiworld link i just gave, but it seems to be broken.  the diagram isn't necessary, because the wiring is pretty simple.

from my old post:

> i'm the guy who posted as AEIOUsometimesY.  the APS25CH is
> the same as the APS25KB but has code-hopping as well as
> double-pulse unlock (allowing you to leave out one of the
> connections in the original diagram).
> using the diodes is simple.  connect the alarm outputs (red
> for lock pulse, green for unlock pulse) to the central
> locking/alarm unit as shown, but replace the two leftmost
> relays with diodes.  you don't need the third connection
> (to pin 5 green/blue on the central locking unit) because
> the APS25CH is capable of sending a double pulse to unlock
> all doors.
> so the connections are:
> red (lock pulse) to diode to pin 4 brown/grey
> green (unlock pulse) to diode to pin 3 brown/green
> power connections as indicated in original diagram
> remember that these are (-) pulses, so the diode should
> be aimed toward the alarm unit (there should be an arrow
> on it indicating polarity).
> if you look at the original diagram, it's obvious that the
> original poster was using the relays as diodes.  i don't
> know why he used relays instead of diodes, which are cheaper,
> solid state (more reliable), much more compact, and easier
> to wire.  the diodes do produce about 0.6v drop in the
> forward-biased direction, but with 12v being supplied, 
> this shouldn't make much difference.

----- Original Message ----
From: Christopher Leal <chris_leal at sbcglobal.net>
To: "fastscirocco_2000 at yahoo.com" <fastscirocco_2000 at yahoo.com>
Cc: "s-car-list at audifans.com" <s-car-list at audifans.com>; Theodore Chen <tedebearp at yahoo.com>
Sent: Tuesday, March 17, 2009 6:26:46 PM
Subject: Re: [s-cars] 94 S4  infra-red key replacement options

Bought the remotes and they look to be good quality. I will let you know how they work once I install them.


Sent from my iPhone

On Mar 11, 2009, at 6:12 AM, chris chambers <fastscirocco_2000 at yahoo.com> wrote:

Any thoughts on this system that comes with "switch blade key" remotes?

Ebay auction #120331094209 or link below.


I'm tempted to replace my bulky IR remote with this system!


--- On Wed, 3/11/09, Theodore Chen <tedebearp at yahoo.com> wrote:

From: Theodore Chen <tedebearp at yahoo.com>
Subject: Re: [s-cars] 94 S4  infra-red key replacement options
To: "Christopher Leal" <chris_leal at sbcglobal.net>, s-car-list at audifans.com
Date: Wednesday, March 11, 2009, 3:23 AM
chris, i put a prestige APS-25CH into my '92 a long time
ago, and can lock/unlock my car from 50 feet away.  i could
have gotten a more expensive alarm system, but all i wanted
was the RF remotes.  i'm not wild about the somewhat
cheap remotes, but they have worked well for several years
and the system was less than $40.  most alarm systems will
probably work, as long as they ground their outputs to
activate, and double pulse to unlock.

referring to the audiworld diagram, the relays are
unnecessary extra wiring (besides drawing more power and
decreasing reliability due to their mechanical nature).  i
wired diodes in-line and had no problems at all.  let me
know if you need help wiring.


----- Original Message ----
From: Christopher Leal <chris_leal at sbcglobal.net>
To: s-car-list at audifans.com
Sent: Tuesday, March 10, 2009 8:19:23 PM
Subject: [s-cars] 94 S4  infra-red key replacement options


Finally tired of replacing batteries and the crappy range I
have with the infra-red key locking/unlocking. On a jeep I
had I wired up a cheap aftermarket fob that gave me extended
range. I noticed on Audiworld someone did this on their A4:
http://www.audiworld.com/tech/elec52.shtml  Has anyone found
better options for replacing the existing system? Maybe an
upgrade to later Audi components with the RF capability?

Any guidance is appreciated.

S-CAR-List mailing list
S-CAR-List at audifans.com

S-CAR-List mailing list
S-CAR-List at audifans.com

More information about the S-CAR-List mailing list