96 disco - immobiliser intermittent fault

Usual failure point is the alarm spider. The pcb solder breaks down...

Had exactly the same problem with 110 300 Tdi CSW, two button remote alarm. A known fault with the spider unit that develops an intermittent refusal to de-mobilise hence ligyts but no starter action no engagement. Wait a while and the damn thing starts of its own accord. LR assistance insisted it was the stater and like an idiot I had it changed £300. Problem still present, Roberts Country Vehicles and the contributers here came up with the answer. The upgrading of the spider unit with a LR upgrade, £ 250. Basically it does away with the installed immobilliser and is replaced with a seperate one, that links into the alarm. Two green fobs and a master programming fob complete the upgrade. Pain in the arse is that you wave the fob in the desired place and two beeps later you have 15 seconds to start car. Switch off and after5 seconds it arms itself so you have to remove the key and disarm it agin before going off, irritating when waiting for wife to do shopping.

John H

WTF is a spider unit? My alarm fob (two button) sometimes takes numerous attempts to unlock the doors and yes sometime the starter motor doesn't turn immediately the key is turned but if the key is kept turned it does start. More of an annoyance than a problem.

Peter.

It's a small box that, on a Disco, lives behind the radio underneath a metal plate. To get to it you have to remove the centre console of the dashboard.

It switches 3 circuits on when the alarm is deactivated - ignition, fuel pump and starter. On a diesel it controls the fuel solenoid, the starter and the fuel pump IIRC.

The problem is that it is so badly made (usually dry joints internally) that one or more of the circuits become high resistance resulting in a range of, often intermittent, problems.

On my V8 the first circuit that failed was the fuel pump, we initially thought it was a problem with the LPG system as it would sometimes refuse to run when we changed back to petrol. I bypassed this circuit and installed my own immobiliser into the circuit.

The next circuit to fail was the ignition circuit which caused intermittent starting - I eventually figured out that the ignition circuit was so borderline (high resistance) that I got no sparks while cranking but sometimes it would start if you caught it right as you stopped cranking after which point it would work OK.

I bypassed the ignition circuit and, again, fitted my own immobiliser.

Now I'm waiting for the starter circuit to fail..... when it does, I'll bypass that too and maybe fit an aftermarket immobiliser instead - a Clifford one maybe. I have a bypass wire already installed so that if it fails I can bypass it quickly and easily.

All my bypasses were done without having to get to the spider - if you get to the spider and want to remove it altogether, Land Rover supply a small cable assembly which replaces it - costs about a fiver and saves tapping into the wiring.

cheers

Dave W.

hey thanks guys

much appreciate this

will go get one and sort it out - but sounds great fun to replace ha!!!!!

not sure if i fancy changing the whole thing and upgrading though

probably just got with replacing the spider

thanks again

snip

Thanks very much for the info, at the moment all is fine and I can live with having to press the fob a couple of times, but I'll keep this e-mail as a reference for the future.

Cheers

Peter