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Spanner

Member Since: 16 Nov 2017
Location: Pembrokshire
Posts: 10

Break inertia switch circuit to disable Defender

Hi all,

Recently bought a TD5 110 CSW and immeadiately got paranoid about security. I've bought a steering lock and pedal lock ('ardcase) but have been pondering whether it's reasonable to add a switch to the inertia cutout switch under the bonnet to disable the car. Have done a bit of searching but can't find whether this is safe/practical to do?

Thanks for any advice.

29th Dec 2017 11:55am

roel

Member Since: 08 Aug 2009
Location: Lelystad
Posts: 2039

I am not an expert on this but this is a possibility but there are more.
The best protection is I think that the starter motor will work but the engine won't start. I think the thieves don't like noise. If the starter motor is't doing anything it takes time but it doesn't make noise so they have time for looking for the problem.

I am not sure what the inertia switch does. There are ways to prevent the engine starting even when the starter motor is turning over the motor. Roel

1984 90 2.5 na Diesel - RR V8 (1994-2001)
1997 Camel Trophy Discovery 300TDI (2001-2009)
2005 G4 Discovery III 4.4 V8 (2008-2018) It's gone but it still hurts.
2003 90 Td5 (2009-now)

29th Dec 2017 10:20pm

Spanner

Member Since: 16 Nov 2017
Location: Pembrokshire
Posts: 10

I agree regarding the noise from the Defender starter but I've yet to come across a way of doing this that matches my beginners knowledge of Defender wiring.

The inertia switch is designed to cut off the supply to pretty much everything in the event of an accident and is just a normally closed switch so another switch in series will break that circuit and cut off any way of starting the engine, even the supply to the ECU.

It's "silent" so not ideal but from what I've read on various forums if you leave a Defender anywhere, for any length of time, someone will nick it so I'm looking for something I'm capable of doing fairly soon.

29th Dec 2017 10:50pm

bankz5152

Member Since: 02 Feb 2017
Location: South London/North Kent
Posts: 2147

Can always unplug the injector harness, itll crank over and over but never start unless its plugged back in.

29th Dec 2017 11:21pm

grafty99

Member Since: 15 Aug 2012
Location: North Devon
Posts: 4785

just unplug the inertia switch on the bulkhead

2002 90 Td5 Station Wagon
1990 Vogue SE
Triumph Tiger Explorer 1200
Td5 90 Thread http://www.defender2.net/forum/topic50767.html
Tdi 110 Thread https://www.defender2.net/forum/topic69562.html
RRC Thread http://www.defender2.net/forum/topic54492.html
Instagram http://www.instagram.com/george_grafton

29th Dec 2017 11:52pm

Spanner

Member Since: 16 Nov 2017
Location: Pembrokshire
Posts: 10

To demonstrate my extensive knowledge, I think what you're referring to is under the bonnet.If so, I might get spotted unplugging it!

29th Dec 2017 11:54pm

Spanner

Member Since: 16 Nov 2017
Location: Pembrokshire
Posts: 10

Just found a video on YouTube and if the Defender is similar to the Discovery then my idea won't work as the hazards are activated when the inertia switch is open.

Looks like its back to the drawing board.

30th Dec 2017 10:41am

Procta

Member Since: 03 Dec 2016
Location: Sunderland
Posts: 5147

roel wrote:
I am not an expert on this but this is a possibility but there are more.
The best protection is I think that the starter motor will work but the engine won't start. I think the thieves don't like noise. If the starter motor is't doing anything it takes time but it doesn't make noise so they have time for looking for the problem.

I am not sure what the inertia switch does. There are ways to prevent the engine starting even when the starter motor is turning over the motor.

what it does is kill the power to the fuel pump, if you have a crash. Also they known to fail too, so if the defender will not fire into life and the engine just spins over and over. This switch could have either tripped or the contacts failed in side the switch. I have had one trip out on me going over a speed bump

what the OP wants to do is make a plug and play harness with a switch on that bridges the fuel pump and the main loom.
Mount the switch somewhere hidden and you are a way.

Defender TD5 90 ---/--- Peugeot 306 HDI hatch back

Success is 90% Inspiration and 4 minutes Preparation # you can make it!

30th Dec 2017 11:39am

Spanner

Member Since: 16 Nov 2017
Location: Pembrokshire
Posts: 10

Could you explain what you mean by bridging fuel pump and main loom? I'd read somewhere that the td5 will run (roughly) without its fuel pump.

31st Dec 2017 9:20am

TJH1985

Member Since: 22 Aug 2016
Location: Midlands
Posts: 238

My TD5 will start and do 35/40 without a working fuel pump, all feels normal except a lack of power. So wouldn’t stop it being pinched IMO.

31st Dec 2017 9:34am

grafty99

Member Since: 15 Aug 2012
Location: North Devon
Posts: 4785

Mine won't start and the hazards don't flash with it unplugged. I think the hazards flashing is a discovery thing

Also, they don't know what you're doing under there, you can disconnect without it being obvious. Just leave the plug in place but disconnected

31st Dec 2017 6:41pm

grafty99

Member Since: 15 Aug 2012
Location: North Devon
Posts: 4785

Btw mine is on a hidden switch but until I wired it in I disconnected it manually if needed. Once you're in the habit it really don't take long

Also applies to the 2.2 puma as well 2002 90 Td5 Station Wagon
1990 Vogue SE
Triumph Tiger Explorer 1200
Td5 90 Thread http://www.defender2.net/forum/topic50767.html
Tdi 110 Thread https://www.defender2.net/forum/topic69562.html
RRC Thread http://www.defender2.net/forum/topic54492.html
Instagram http://www.instagram.com/george_grafton

31st Dec 2017 6:44pm

Spanner

Member Since: 16 Nov 2017
Location: Pembrokshire
Posts: 10

I'm going to do this once the weather allows me to open the front door. A forum user (many thanks) has pm'd me an alternative way of switching which makes the whole thing seamless to use.

31st Dec 2017 7:11pm

Procta

Member Since: 03 Dec 2016
Location: Sunderland
Posts: 5147

Spanner wrote:
Could you explain what you mean by bridging fuel pump and main loom? I'd read somewhere that the td5 will run (roughly) without its fuel pump.

basically make a plug in play harness with switch, that plugs to the fuel pump and to the loom ( the main loom) saves you cutting wires etc. So all you do is switch the power off.

If its running roughly with out the fuel pump, sounds to me that it might have a secondary one in the engine, that's powerful enough to still feed diesel through. Defender TD5 90 ---/--- Peugeot 306 HDI hatch back

Success is 90% Inspiration and 4 minutes Preparation # you can make it!

31st Dec 2017 7:35pm

zsd-puma

Member Since: 09 Aug 2016
Location: Kent
Posts: 2720

2010 Defender 110 Puma 2.4 USW Santorini Black

Quote:
If its running roughly with out the fuel pump, sounds to me that it might have a secondary one in the engine, that's powerful enough to still feed diesel through.

The injection pump will be able to suck a certain amount of fuel from the tank, but not enough to make the vehicle perform fully, so they fit an extra electric 'lift pump' in the tank to assist the injection pump.

31st Dec 2017 9:07pm

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