Removing Immobiliser HELP

[RNC93]

Hi all !
I have a 1989 320 ,
When I bought the car it came fitted with a Sigma Alarm & Immobiliser , Recently the alarm has stopped working and the Immobiliser seems to be causing havoc resulting in problems getting the car started (tried all 3 fobs).
Has anyone got any idea where the main components may be located so I can try remove it.
Thanks in advance !

[Speedtouch]

They are usually installed behind the glovebox, and the unit and associated wiring should be fairly obvious as aftermarket add-on stuff.

[Brianmoooore]

They are usually installed behind the glovebox

Unless they are of the type that the alarm sounder is built into the same case as the electronics, such as the Piranha alternative OE E30 alarm, in which case it will be somewhere under the bonnet - usually the LH inner wing, or the front battery tray on E30s with a rear mounted battery.
In any case, the sounder should be somewhere obvious, so following the wiring from that should give some idea as to where the rest is.
The immobilised circuits of the car will probably be one or more of a plain green wire, a black/yellow wire, and a green/purple wire.
These will have been cut, and the cut ends connected to the immobiliser, so you will have to remove the immobiliser and join the cut ends back together.
All other wires can just be traced to where they connect to the car wiring, and removed, making good any damaged insulation.