Doors Don’t Lock Anymore Using the Alarm, Alpine 8040

Hello All,

I’m having a problem with an Alpine alarm (8040) installed back in 1992. The doors don’t lock anymore when I activate the alarm. All other alarm features are working, lights, siren, radar, valet switch, LED, door sensors and remote. After locking the doors manually using the stock CDL (more on that) then activate the alarm, the alarm will unlock the doors when I use the key fob to turn off the alarm.

Stock CDL (Central Door Lock system) Taken from the Service manual…

Central door locking actuators are fitted to both doors so that when one door is locked or unlocked, using either the exterior key barrel, or interior sill lock rod, the opposite door will be operated in a similar manner after a half second delay. The doors should be locked only when both doors are fully closed, as if a door is locked when either door is open, or only closed only on the first latch (ajar), the CDL will operate first to lock both doors, but then after a two second delay, will unlock the doors again.

When both doors are in an unlocked condition, both lock sensing switches are closed to earth. If one door is then locked, the lock sensing switch on that door is opened. The ECM processes this signal, and after ~ second delay, operates both actuator motors by supplying 12 volts to terminal A, and a ground to terminal B. Both lock sensing switches are open. If one door is then unlocked, the lock sensing switch on that door is grounded, and the ECM operates the actuator motors by supplying 12 volts to terminal B, and a ground to terminal A. If an attempt is made to lock the doors when either door is open, or closed only on the first latch, the system will first operate as above to lock both doors, but then the ECM receives a signal from the door ajar switch that both doors are not fully closed, and after a 2 second delay, unlocks the doors.

Since I’ve never worked on alarm systems I can’t really troubleshoot the system. I swapped the relay used for the lights with the door lock relay and the lights still work and the door doesn’t lock so I don’t think it’s a bad relay. I recently had to fix a bad MAP sensor wiring issue under the dash and might have inadvertently disconnected something for the alarm. As far as I can tell everything is connected. Below is what's connected to the door lock relay.

85 - Alarm, Door Lock
86 - +12V
87 - open (not used)
87a - Alarm, Door Unlock
30 - Tapped into the right hand side CDL Lock Sensing Switch wiring

Any help is much appreciated

Thanks,
Wayne

Sorry,

Didn't set up my signature yet. The car is a 1991 Lotus Elan LHD USA model.

https://www.the12volt.com/relays/relaydiagrams.html

Look at diagrams 21 and 22. They are the only ones I can find for type F door locks. According to Directechs that vehicle has type F one wire locking system.

Thanks for the help. It's working now with a diode and re-wiring the relay. I don't know how it was working before. Very very strange.

Thanks again.