Installing an immobiliser

[Giles]

Hi - back on the Stag now!

I am just in the process of putting in a Immobiliser. Standard sort that isolates 2 circuits - starter and one other ( eg.fuel pump or ignition). Instructions are fairly vague but it seems you just cut the wire you want to isolate and connect the two ends to the two relevant wires on the unit. It says 18amp relays are used for these circuits which I assume are in the unit.

My slight concern is that the white/red wire for the starter solenoid on the Stag are a lot thicker than the ones on the immobiliser which I would have thought were a bit thin for 18amp but I am only guessing!and is 18 amp enough?

Anyone else fitted their own and come across this? Or am I worrying about nothing

[GDPR]

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It's not the size of the wire per se, but the number of strands and the strand thickness - i.e. cross-sectional area of the conductor - that counts.

Many modern wires look smaller because of advances in insulation materials and technology that coats the wire, so the odds are that the wires supplied are good for at least 15 amps as the relays are rated at 18.

Hope that helps put your mind at rest

Russ

[Giles]

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thanks Russ.

I have had another look and the wires are marked .75mm2

- do you reckon 18 amp is ok for the solenoid - I assume it does not draw more than that despite the quite chunky wire?

[V8 Rumbler]

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Giles wrote:

thanks Russ.

I have had another look and the wires are marked .75mm2

- do you reckon 18 amp is ok for the solenoid - I assume it does not draw more than that despite the quite chunky wire?

I would double check with the manufacturers. I think 0.5mm thinwall is rated at 11amp and 1mm thinwall at 16amp. So you could be borderline.

Darren

[Giles]

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thanks - I will try and give them a ring - suppose I might have to put another relay in and let the immobiliser switch that - this is getting complicated now!!:shock:

[V Mad]

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Wires are rated for continuous current. The starter is only operated intermittently therefore you can pass much more current without the wire suffering any damage. I am not impressed with the relay rating of only 18 amps though. I would prefer to use at least a 40 amps one.

If you want to reduce the load on the starter circuit (ignition switch, inhibitor switch, connectors etc) you could fit one the EJ Wards starter relay kits. Then your immobiliser would be quite happy

[DJT]

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As per a recent thread on immobilisers, I bought a Maplin A17HB. The instructions are really basic and I don't recognise one of the symbols. I have contacted Maplins and they tell me they have contacted the manufacturer, but I haven't received any confimation yet. Anyone here help?

Dave

[V Mad]

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It looks like a toggle switch to me. They have drawn the symbols pictorially not using the recognised electrical symbols. Quite what the switch does is anybody's guess, you will have to see.

[GDPR]

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I agree Chris - my guess it's an immobiliser bypass switch for when the car would go in for servicing

[DJT]

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Thanks Chris & Russ.

Just received an email from Maplin. They say it is the 'High Voltage Coil'. Thought it might be, but the indication that it drops to earth confused me. Looking again at the Stag wiring diagram I can see that they have combined the coil and dizzy in one:

Dave

[KOY 23]

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Hello Dave.

It looks like there are 3 immobilised circuits. It is not a switch, although it looks like one. The coil makes sense from an electrical point of view.

You pick whatever you want to isolate, but if you put it in series with the ballast resistor, the car will fire then stop, confusing the scroat into thinking it is a fuel problem. If he can think that far .

If you cut the starter, I suggest that you use a relay in the starter low current supply to avoid the "click nothing" problem. The Stag solenoid takes a fair current and the additional resistance of immobiliser wiring and its relay, may cause problems in time.

You may need to put in another relay to give you a negative pulse from door switch, If you have 1 wire on your door switch you are ok but I think this happened on Stags from LD35000 ish.

Suggest that you do not cut the wire of the circuit to be immobilsed and connect both immobilser wires at that point as it is immediately obvious what has been done. If you make the 2nd connection some way downstream it is not so obvious. Black tape to bind wires along the loom all adds to the mystery. Solder and heatshrink insulation and you will be fine. This is why decent installations are expensive as it takes time to do it neatly and properly.

[DJT]

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KOY 23 wrote:

Hello Dave.

It looks like there are 3 immobilised circuits. It is not a switch, although it looks like one. The coil makes sense from an electrical point of view.

You pick whatever you want to isolate, but if you put it in series with the ballast resistor, the car will fire then stop, confusing the scroat into thinking it is a fuel problem. If he can think that far .

If you cut the starter, I suggest that you use a relay in the starter low current supply to avoid the "click nothing" problem. The Stag solenoid takes a fair current and the additional resistance of immobiliser wiring and its relay, may cause problems in time.

You may need to put in another relay to give you a negative pulse from door switch, If you have 1 wire on your door switch you are ok but I think this happened on Stags from LD35000 ish.

Suggest that you do not cut the wire of the circuit to be immobilsed and connect both immobilser wires at that point as it is immediately obvious what has been done. If you make the 2nd connection some way downstream it is not so obvious. Black tape to bind wires along the loom all adds to the mystery. Solder and heatshrink insulation and you will be fine. This is why decent installations are expensive as it takes time to do it neatly and properly.

Thanks,

I fitted a similar unit to my previous Stag, but that only isolated2 circuits. As I always take the positive feed for the Lumenition from the output of the fuel pump cutoff, isolating that effectively cut the ignition as well. I think with this oneI shall cut the ignition at a second location which will be 'belt and braces'.

The door switch always causes problems as they are not the normal 'drop to earth' type. As you say, a relay will be required here, which I have got. Something else to do over the next few days.

Dave

[Giles]

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V Mad wrote:

Wires are rated for continuous current. The starter is only operated intermittently therefore you can pass much more current without the wire suffering any damage. I am not impressed with the relay rating of only 18 amps though. I would prefer to use at least a 40 amps one.

Spoke to the manufacturers today - they said the same - the wire is fine as the starter is not a continuous draw even if you are having problems they assured me it would be fine. Asked about the relay and they said that 18amp was the continuous rating and that the same applies and that it will happily cope with a starter.

Thanks for your help as I am a sceptical type who would not want to just take their word for it!

[V Mad]

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You will probably be OK with an 18 amp relay as the relay does not normally have to switch while current is flowing, it just isolates the circuit.

For the EJ Ward mod to the starter circuit they use a 40amp relay as I recall and this has to actually switch the current on and off. My local Auto Electrical specialist says he would never fit anything less than 80amps!

[Stagdad]

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DJT wrote:

. As I always take the positive feed for the Lumenition from the output of the fuel pump cutoff,

Dave

Thats a blo0dy good idea Dave