Greetings, I am hoping for some direction in solving some electrical issues related to the central door locking/alarm system in my '96 Disco with the Lucas 10as.

Some background: I've owned the truck for two years and have driven 60 miles everyday for my commute. The PO worked at a ski resort in Montana so it has spent years in harsh wet conditions. After tacking the usual D1 mechanical issues, the alarm staring acting up. Recently I lost all ability to get past the immobilizer with the key (truck was missing key fob when purchased).

I towed it to Lamorna Garage (awesome Independent); 2k later diagnosing electrical issues, the problem was traced to a severely corroded header joint. After the repair the truck ran great (when it would start). So now when I go to unlock the truck with the key, about 50% of the time the alarm fails to disarm (red solid alarm status in "start" key position with just a relay click from passenger footwell). So I get out of the truck and lock and unlock until it starts.

The central door locking had worked the whole time until sudden death the other day. Luckily I had a spare known working master door lock actuator and replaced it, no change. Next I bought a key fob/programmer and synched it through the OBDII port, no response from the key fob.

Symptoms:
-Alarm works when it wants to.
-Alarm doesn't seem to respond to key fob commands (hard to verify).
-Central Door Locking is dead, but worked 100% untill recently.
-Unlocking door with key doesn't reliably shut alarm off.

What I've done
-Replaced master door actuator.
-Verified mechanical function of the master key position switch inside driver's door.
-Synched new 315MhZ two-button key fob from remotekey in the UK.
-Checked every relevant fuse.
-Removed sunroof fuse due to unrelated issue

All this leads me to believe that the Lucas 10as, a relay, or a wiring fault is to blame, and I'm wondering a few things. I want to try to do as much as I can before surrendering it to a local shop.

-Can I remove the Lucas 10as to check for dry solder joints/shorts on the circuit board without disrupting the link between the ECU and Alarm? Or will this result in loss of synch and a trip to a shop with a Hawkeye/testbook/nanocom?

-If I buy a volt meter and learn how to use it, is there a diagnosing process I can do to verify what's the culprit in the CDL/Alarm system?

-If I can remove the Lucas 10as, what is the most efficient way to get it out? Unplug the wiring headers and it's out?

-What's estimated out-of-pocket for a working alarm/ecu swapped into my truck at a local shop?

-What should I do?

Thanks Everybody, I'm never giving up on this thing!

 

Update - I was able to get at the green alarm box (amr4885) and noticed that the tabs securing it to the kick panel were busted and the tabs that secure the green wiring header joint were busted, someone has messed with this thing before. Still haven't unplugged anything for fear of losing ECM synch.