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Discussion Starter · #1 ·
Hey everyone, I was wondering if I could get some help with installing a cruise control unit on my 06 Elise? Specifically with the brake light wiring.

I purchased the kit from Conrad Anderson in the UK and it's Lotus specific. Most of the install was fairly easy, but I'm stuck on the brake wiring. I found the wire that gets 12v when the brake pedal is depressed (green/purple) and according to the directions, it should be connected to the brown wire. I assumed the brown/wire wire would just be attached to the one next to it (green/yellow). I tried the programming the unit and the troubleshooting points to the brake wiring. I reversed the wires with no luck.

I've attached instructions from the manual and what I see under the dash. Any advice?
 

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Per the wiring diagrams, the dual green/purple is the wire that heads out to the brake lights
Their instructions are contradictory, pretty sure it needs to be the gn/pu, the other one is power all the time when the ignition is on
 

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Do you have voltage at the fuse? Is ign key on when you're testing?
 

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Discussion Starter · #5 ·
Do you have voltage at the fuse? Is ign key on when you're testing?
I have voltage on the fuse (F5) and ignition was on when I tested on the cable in the car. I haven't had any brake light issues with the car before starting the install.

I keep rereading the instructions, but I feel like I'm not missing anything. I found the wire with voltage with the brake pedal depressed and spliced it (brown). Spliced the other wire (brown/white) to the only other brake wire.
 

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Check for voltage on orange wire with ign switched on

Check for voltage on brown/white wire to green/yellow connection

brown should connect to green /purple
 

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Discussion Starter · #9 ·
Check for voltage on orange wire with ign switched on

Check for voltage on brown/white wire to green/yellow connection

brown should connect to green /purple
The unit lights up and goes through the initial diagnostic, so I'm pretty sure the orange wire is good. I'll recheck voltage though.

Thank you for the confirmation of the brown wire to green/purple. I'll recheck voltage for the brown/white wire as well.

I'll report back this weekend to see if there's any progress. I'll have to leave it disconnected for now. No cruise control for me for the seven hour drive tomorrow:(
 

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Discussion Starter · #10 ·
I have a vested interest in this, I have one of these kits in a box waiting for me to get a round tuit
Everything was pretty simple up to this hiccup. I followed one of the writeups here and it was pretty helpful for mounting the clutch switch. This was the only part left somewhat unclarified.

Hopefully I'll have more resolved for the future.
 

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(green/purple) and according to the directions, it should be connected to the brown wire. I assumed the brown/white wire would just be attached to the one next to it (green/yellow).
This seems correct to me.

From the manufacturer:

Grey Font Pattern Magenta Number


Did you measure the resistance across both wires with the pedal released ? Do you have the 3rd braking light ? Standard bulb or LED too?

Because the braking LED lights have probably a quite high resistance, maybe too much to satisfy the module.
 

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Discussion Starter · #13 ·
This seems correct to me.

From the manufacturer:

View attachment 1320976

Did you measure the resistance across both wires with the pedal released ? Do you have the 3rd braking light ? Standard bulb or LED too?

Because the braking LED lights have probably a quite high resistance, maybe too much to satisfy the module.
I did not mesure the resistance, but I will check it as well. I don't have the third brake light, but I do have the GRP V3 tail lights. I haven't replaced any other bulbs to LED.

The only resistor this write up I'm using was for the VSS wire: Drive-by-Wire Cruise Control - installation report

Does this mean I should try splicing the yellow one to the brown wire? I really appreciate the help from everyone! I admittedly an not the best at electronics or wiring.
 

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Does this mean I should try splicing the yellow one to the brown wire?
No, green/purple to the brown wire is correct. Can you put a light bulb (about 21W) across both wires, or where the 3rd light braking should be? It could be an easy test.

A braking light bulb of 21W has about 6.8 ohm, what about your GRP V3 tail lights, I would not be surprise to see x 20 more...
 

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Hmmm

It is possible that the LED does not provide the 'ground' that is required by the circuit.
You literally have to get 12 volts or your brake lights won't work.
But an LED won't necessarily show as ground when off, and a digital circuit might need to see both 'high' and 'low'

Inserting a fairly high value resistor[say a 1k ohm] between the gn/pu wire and ground [essentially across the brake light bulb]might satisfy the need for ground without affecting the operation of the lights. It is possible it is only needed for setup although I am not sure.
 

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Discussion Starter · #17 ·
No, green/purple to the brown wire is correct. Can you put a light bulb (about 21W) across both wires, or where the 3rd light braking should be? It could be an easy test.

A braking light bulb of 21W has about 6.8 ohm, what about your GRP V3 tail lights, I would not be surprise to see x 20 more...
I will give that a shot. I should have clarified as well, the instructions say the yellow wire with the resistor is not used. I would snip that off and splice into the brown and green/purple wore connection.
 

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Discussion Starter · #18 ·
Hmmm

It is possible that the LED does not provide the 'ground' that is required by the circuit.
You literally have to get 12 volts or your brake lights won't work.
But an LED won't necessarily show as ground when off, and a digital circuit might need to see both 'high' and 'low'

Inserting a fairly high value resistor[say a 1k ohm] between the gn/pu wire and ground [essentially across the brake light bulb]might satisfy the need for ground without affecting the operation of the lights. It is possible it is only needed for setup although I am not sure.
That seems like
This does give a course of questioning for their tech support, IOW function with LED brake lights
I will try what you said in your previous post as well.

I figured since it was a configured for an 06+ car that it wouldn't matter. Maybe the other owner has stock LED everything and it wasn't a factor for him.
 
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