I, too, installed a cheap keyless entry module to my 87 S4 that already had the factory alarm -- VERY easy and used very often. The wiring diagram posted by Ed looks very much like my install.

I also did the keyless trunk relay. The only thing I did different on the trunk install was that I changed the trunk actuator to ground always so I could use the keyless entry with my groceries and not have to have one of the doors open. (I think the factory actuator is only grounded when one of the doors is open as a safety precaution so the trunk doesn't open accidentally while driving.)

 

Doug - Yes I had the same issues with the hatch release initially. I ended up modifying it too - but I did preserve the lockout for the manual release - just in case.

Tiburon _ I guess I should have created a full write up last time - Roger and I just batted it back and forth till I'd spilled all the beans.

I will dig out some detail and post more - it is really pretty easy - parts required amount to (approx):

1 keyless entry system - reasonable ones for $40-$70

1-2 relays & sockets (1 for hatch, 1 for horn possibly one more for lights but many keyless systems have one internal relay)

~10 Insulation displacement connectors (good ones only)

Tools
I'd suggest some shrink wrap tube and a heat gun and a soldering iron, solder, wire strippers, some color coded cable (esp for hatch) and factory manuals.

Alan

 

Alan - Thanks. I am looking for a summer project. And a keyless entry would be a great one.

Tib

 

Tib,

You could come up and powdercoat my intake and valve covers if you can't find anything else to do.

 

Alan, et al.:

I would like to hear more about the best way to do the trunk release. I installed a keyless entry, but currently just for the doors. Works well. But I was a bit stumped about how to do the trunk due to the door open requirement, which I would like to preserve for the interior release, as well. Please give electrical advice. Thanks!

 

Bill,
The configuration of the hatch unlock is that the pull switch is to Battery+ this is wired back to the hatch release motor +ve. The other side of the hatch motor is connected to the switched ground for the interior light - thus a door has to be open for the trunk to release, a safety lock out - the trunk release motor has a single cycle run interlock mechanism built in.

What I did was to totally change the way this is wired - there really isnt a very simple way, but acrually not too bad..

I connected the -ve side of the hatch motor to permanent ground.

The positive side of the hatch motor now goes to a new relay (main contacts) with a fuse in series to Battery +ve. The relay coil goes to +ve battery on one side and 2 paths for the negative side:

1) The -ve O/P from the hatch release on the keyless entry

2) A wire across the car to the hatch switch - the other side of
the hatch switch now connects to the switched ground for the interior lights.


This 2) connection is not so bad because you can use the existing line from the switch to the rear hatch to run the (now disconnected) switched ground back to the hatch switch. I installed the keyless entry next to the passenger seat - so I needed to run a new line from the relay back to the hatch on that side of the car anyway. In my car year the alarm guts are under the passenger seat.

So really just 2 new wires - 1 from the hatch switch across to the Keyless entry module / relay and 1 from the Keyless entry / relay back to the hatch motor.

Note that the -ve hatch unlock from the keyless entry must also be connected to the hatch disarm connection to the Factory alarm to avoid the alarm going off when the hatch is opened (this alarm input comes from the hatch key).

The switch and the remote button now operate via the Relay to open
the hatch.

An extra implication of this setup is also interesting - as you turn the key to unlock the hatch the hatch relay triggers and electrically releases the hatch... Voila!

Hope this helps

Alan

 

I have just installed an aftermarket alarm combined with electric central locking after removal of the vacuum system in a 78 928 - its a bit of a mission but well worthwhile