Immobiliser fitting - best circuits to 'cut'?

Hi folks,

Before I put the dash back in I thought I'd fit an immobiliser. I had one in years ago, but it packed up so I removed it completely and tidied up all the wiring. Anyways, the one I have bought can cut 2 circuits, but they have a 10 amp max limit. I was thinking of fuel pump and coil supply.
Questions:

• are either of those > 10 amps?
• Should I cut the supply to the relay 'coil', or the supply to the fuel pump?
• Anything better I could 'cut'?

Oh, it's an 83 tin-top.

Ta!

J

paceman said

Hi folks,

[*]Should I cut the supply to the relay 'coil', or the supply to the fuel pump?[/*]

If it can do 2 circuits it would be "AND", not "OR".

Also you don't mention if its fuel injection but obviously the carb car doesn't have a fuel pump, so you'd not have that circuit to alter.

Personally I would cut the control side of the fuel pump relay. Leave the main current side alone. It will do the same job without worrying about the high current. The ignition live to the coil can be run through the immobiliser or the live to the TCI will immobilise the car and will use less current.

I'm thinking of doing the fuel pump with my tracker.

When you say "the control side of the fuel pump relay" is that  D13 red/yel - trigger for fuel relay?

Assuming you have the ce1 fuse box with blade fuses, you could cut red/black D26. The car would still start from the fuel pump prime but soon cut out when it's not seeing a signal from the coil.

Is that the least dramatic way?

Hypothetical situation is that they have stolen the car and are driving. They pass through the geofence so the tracker cuts a circuit. Don't want them to have an accident and damage the car.

So does the tracker allow them to steal the car and stop them later? Sorry don't know nothing about tracker. Cutting the fuel pump would be the same as running out of fuel.

Well its primary function is to track. So I can find out where it is, where it's headed, and how fast. But yeah, you can get various combinations with alarm too.

You can set it to alert you if it moves, goes outside a certain area, beyond a certain speed etc. Bizarrely enough you can actually call it and hear what's happening inside.

Some have the option to cut a circuit either by text message or if certain conditions are met.

Thanks chaps,

I think I'll do the fuel pump relay and the TCI live - hadn't thought of that one.
Now I just have to get behind the fuse box which will be fun - too many wires!

J

the_whip said

Is that the least dramatic way?

Hypothetical situation is that they have stolen the car and are driving. They pass through the geofence so the tracker cuts a circuit. Don't want them to have an accident and damage the car.

I'd cut the fuel pump circuit. As Steve said it will be like running out of fuel so they would have time to 'react' to it.

paceman said

Thanks chaps,

I think I'll do the fuel pump relay and the TCI live - hadn't thought of that one.
Now I just have to get behind the fuse box which will be fun - too many wires!

J
If you go done this route, you can do all you wiring in the engine bay . If you take the spade terminals out of there connectors(at the coil) you wouldn't need to chop wires and it could be put back to standard at any time. Just hide wires so it can't be seen.

the_whip said

Is that the least dramatic way?

Hypothetical situation is that they have stolen the car and are driving. They pass through the geofence so the tracker cuts a circuit. Don't want them to have an accident and damage the car.

I'd cut the fuel pump circuit. As Steve said it will be like running out of fuel so they would have time to 'react' to it.

Cheers guys.

Right, so I've dug out the Haynes and reckon I've hit a problem already.

I can cut the coil wire easily enough, as illustrated here:



But the supply to the fuel pump relay 'coil' is a bit more of a challenge. As you can see in the diagram below, the points I could cut are actually look like tracks that are part of the fuse box as opposed to wires…



I don't think I can actually cut the supply to the fuel pump (G6 in the diagram above) as the current draw of the pump is > 10A (well the fuse is rated at 15A so it's probably close to 10A). Any ideas?

On the plus side, I've finally worked out that the D13, E14, E5 numbers refer to the pins on the connectors - always wondered what they meant!

Thanks,

J
 

Actually, looking at the diagrams a bit more, I reckon I need to cut the switched ignition wire - that looks to feed track 15 which feeds the fuel pump relay 'coil'.
On further examination, I don't actually think the fuel pump would run anyway if I cut the Coil wire I indicated as that forms part of the relay 'coil' circuit…
You'd never believe I did electrical/electronic engineering at uni would you!!

As I mentioned earlier, you can cut the red/black d26 this will also disable the pump relay. You can also do it in the engine bay at the coil.

Thanks Steve, must have missed that!

J

Just try unplugging the plug with the green and red/black wires from the coil. Now plug it back on with just the green spade on a terminal. Start the car,  it should run for a short while and stall. If that happens then you know your good to go on chopping that wire.

I fitted an immobiliser last year while I had the dash out, the first circuit I protected was the ignition, the thickest of the 2 black wires at the ignition, easy. For the second it wasn’t so easy for me as my cab is a clipper so carbed, hence no fuel pump relay.

To protect a second circuit I fitted a hard start relay on the starter, as the switched side of the relay draws very little current its ideal for an immobiliser circuit, final result is no ignition and no crank when immobilised, seems to work very well.

For that little bit extra you could always add a push button inline with your starter circuit (when relayed) this means the button needs pressing to crank the starter, bit ott perhaps.

cheers.

Dave,

I did think about the starter as I'm also going to fit a hard start relay (in a nice box alongside my headlight relays). I can immobilise the coil and fuel pump in one go as Steve suggested above, so starter seems like a good 2nd.
Out of interest what size relay did you use? I've got a 40amp one which I feel should be sufficient for the solenoid (given it currently runs through the ignition switch.

J

A standard 40 amp after market relay will do just fine.
You will cut the solenoid wire and one half of it goes to the Contacts the other goes back to the ignition switch.

You will notice afterwards that your starter spins a bit faster as you take the load off the ignition switch and shorten the route of current from the Battery direct to the relay, then from the relay to the starter and the high current never leaves the engine bay.  

Hi J

I used an 80A relay in mine set up, but only because I had some in the garage, I’m sure a 40A will be more than edequate given the vw set up. As Briano states my starter does crank a bit quicker and the high load is now taken away from the ignition switch.

Dave.