12.1V not enough

[fieryfred]

I have had this TVR for 6 years. Theres no mention in the history folder about a change of battery.
So it was no surprise when the cetek charger changed to red at point 6.
Put it on regen & ordered a new battery from tanya next day delivery.
The car is currently in the left hand side of the garage.
Passenger door against boxes of bike parts & ladders.
No problem i thought the regen would be sufficient to start the car.
Turned the ignition on with 12.1V showing & pressed the immobiliser button.
The hazard light began to flash & would only stop when i pressed the immobiliser button again.
So the immobiliser is voltage sensitive.
Its a laser line 996V3 thatchem cat 1 with its own 30amp Penny pleaser.
Is this a good unit or is it time for a change.
I had to move the boxes & ladders to open the passenger door. I have a gravel drive & it was raining stair rods.
So the car stayed inside.
Bad back time lay ahead.
Well the clever folk at TVR left enough spare cable to pull the battery box out to the seat.
The biggest problem was carpet falling all over the place.
The car started first time.
I dont like the Heath Robinson wiring.
The question being is the immobiliser worth changing, or is it They All Do That Sir.

[Belle427]

I cant answer the operating voltage question sorry but if its working ok now id leave it alone.
They can be a pita when they start playing up and also cost a fair bit to change unless your capable of doing it yourself.

[Polly Grigora]

The majority of alarms/immobilisers play up when the voltage drops too low

The 996 was a very good bit of kit

Is your 996 a good bit of kit? Mmm is a tough call, your 996 is old now but possibly not been worked hard

[sixor8]

The Heath Robinson wiring in your 1st photo may have been whoever installed that alarm / immobiliser combo, it not being factory. Admittedly, it's a bit spaghetti-like on top of the battery.

The items in the 2nd photo are the central locking control (this is usually synchronized with the alarm) and the speedo output converter to the ECU (I think?)

If you had a true 12.1V on a decent battery, that should be enough to start the car, unless it cannot supply sufficient current of course so may be toast. Since it has already been messed with, you may need a specialist. Replacement immobiliser / alarms for the originals are available as just remove and plug-in.