The Lotus Cars Community banner

1 - 20 of 303 Posts

·
Registered
Joined
·
60 Posts
Discussion Starter #1
I recently replaced the factory alarm system in my Elise. One of the reasons was the ridiculous range of the stock remote. Even with a new battery, the range was about 1 foot from the driver’s window. Before removing the old cobra alarm system, I tried an experiment and found I could significantly increase the range with a simple modification. If you want to try it, here’s how:

Remove the blank panel from the passenger side dashboard area. Look towards the front and you will see the control unit for the Cobra sitting on a shelf. Using a screwdriver (or skinny fingers), pry the connector locking tabs inwards and lift up the connector. There should be enough wire to pull it out of the access hole.



Next, locate pin 13, which is the antenna wire. It is the black wire on the same end as the pink and green wire. Using a ‘splice & tap’ and a length of wire, splice into the black wire. After reading the next paragraph, put the wire back in the dash (keeping it as free from metal and as extended as possible), reconnect the connector and you’re done.

How long should the piece of wire be? I don’t know exactly, but 36” worked great in my test when I had it lying across the dash (range of about 30 feet!). There is an optimum length, but since I don’t know the frequency, or the characteristics of the factory “antenna”, it is trial and error. I would start with about 4 feet (or about the width of the dash) and cut it bit by bit until you get the best range. Any multi-strand wire will work…the factory wire is about 20 gauge. Also routing it along the windshield frame would probably give better reception. I didn’t try that or try to find the optimum wire length since I was replacing the whole system anyway.

In case you’re interested, I installed a Compustar with remote pager.

Tom
 

Attachments

·
Registered
Joined
·
60 Posts
Discussion Starter #3
The connector was marked (stamped) with tiny numbers that are almost invisible unless the light is just right! But as long as you get the black wire on the same end of the connector with the Pink and Green wire, your are okay.

Tom
 

·
Super Moderator
Joined
·
6,819 Posts
Great info - something I'm definitely going to do this winter! I'll report back with the results.

--Josh
 

·
Registered
Joined
·
46 Posts
TB,
I had a viper(remote pager) installed in my car almost a year ago and "back then" nobody could figure out how to remove the original Cobra alarm...I even asked my Lotus dealership if they could remove it, but they weren't sure if it would screw up my electrical system. So for the last year I have to disarm the alarm with my viper remote then disarm the engine kill with the cobra remote.

Have u been able to disable the factory installed cobra alarm?
Could it be, all I have to do is unplug the wiring harness to the brain u show behind the speaker blank panel?
 

·
Super Moderator
Joined
·
6,819 Posts
I don't know anything about removing the OEM Cobra, but there are simple instructions here on ET on how to set the Cobra to stop arming the immobilizer. It takes about 5 minutes to do. Search for it, it sounds like it would save you a lot of hassle.
 

·
Registered
Joined
·
2,771 Posts
Does anyone have access to a spectrum analyzer that could figure out what frequency our remote uses? You could use a simple BNC connector antenna from Radio Shack, or just a piece of wire stuck into the center conductor as an antenna.
 

·
Registered
Joined
·
1,716 Posts
The remote operates in the 433.050 - 434.790 MHz range, so an optimal 1/4 wave antenna would be 6.802 inches. Seems small, but according to antenna theory, that's the ideal size. Then again, if an antenna of that size would be blocked by metal, you might get more practical range by using a random length of wire that has more "visible" openings between the various metal parts in the dash. You could try using a full wavelength, which would be 27.207 inches.
 

·
Registered
Joined
·
60 Posts
Discussion Starter #9
madguppy said:
TB,
I had a viper(remote pager) installed in my car almost a year ago and "back then" nobody could figure out how to remove the original Cobra alarm...I even asked my Lotus dealership if they could remove it, but they weren't sure if it would screw up my electrical system. So for the last year I have to disarm the alarm with my viper remote then disarm the engine kill with the cobra remote.

Have u been able to disable the factory installed cobra alarm?
Could it be, all I have to do is unplug the wiring harness to the brain u show behind the speaker blank panel?
Yes, you can completely remove the Cobra from the system by unplugging the connector. That's what I did when installing the Compustar. I interfaced all my connections to that connector (door switches, microwave sensor, LED telltale, etc.). One thing I'm not sure of (I don't have the schematics here), is the operation of the fuel relay shutoff. It may not cutout in an accident from the inertia switch. I can check it at home, or maybe someone else has the schematics handy and can comment.

Tom
 

·
Registered
Joined
·
3,826 Posts
The inertia switch only works when the engine is on. It does not rely on the Cobra Alarm at all. When tripped it shuts off the Fuel pump and unlocks the doors.
 

·
Registered
Joined
·
60 Posts
Discussion Starter #12
scottyb said:
The inertia switch only works when the engine is on. It does not rely on the Cobra Alarm at all. When tripped it shuts off the Fuel pump and unlocks the doors.
I'm not so sure. The inertia switch signal does not go directly to the fuel pump relay...it first goes to the immobiliser relay, which is controlled by the Cobra alarm. I don't know the internal wiring of the immobiliser to say for sure that it wouldn't be affected. (And I wouldn't rely on the schematic where it shows a direct connection through the immobiliser since similar indications within the Cobra are not direct).

Tom
 

·
Registered
Joined
·
712 Posts
The antenna is already the correct length. It's just needs to be freed from the rest of the cables coming from the Alarm box.

It turns out that there is even a way to feed it up to the windshield. After doing that, I was able to get over 30 feet (though it was parked in my garage which might have increased the range.) None the less, it is far better than having to be almost in the car to get it to work.

Steps to do this:
- Remove the panel cover (just two screws at the bottom that come out at an angle. Then you'll have to pull pretty hard on the bottom to get it to come out sometimes.)
- Remove the cable pull tie thing. (Black plastic thing that holds the clear plastic around the bundle of cables.)
- Pull the clear plastic far enough away so you can clearly see.
- Find the wire as described above. It was wrapped just outside the rest of the wires on my car.
- Pull the wire out of the taped up group, toward the box.
- Find a better way to mount it.

Extra steps to get it to the windshield:
- If you put your head really down and close to the openning, you should be able to see a light coming through from the windshield just to the right and in front of the speaker.
- I poked a hole in the side of the clear plastic so that it would have a shorter path to the front.
- Get something to grab the wire when it sticks out the top, like needle nose plyers.
- Take the wire and carefully thread it into the hole until you can see it come outside the other side.
- Grab it with the needle nose plyers
- Pull lightly on the cable to get it all the way through
- Then I taped it to my windshield mostly out of view. Once the cable gets set though, it's unlikely to move much, and I could probably have just let it dangle there.


I found this when, I went to try the previously mentioned solution, and I was having great trouble getting the wire harness unplugged from the alarm box. So, I was thinking of tapping into the wire a little further down the line. And I discovered it was wrapped just outside the other wires in the bundle. So, I traced the wire about 2 more inches to find that it ended. Then I performed the steps above.
 

·
Registered
Joined
·
853 Posts
About 110' clear and 60' with structures

usofrob said:
The antenna is already the correct length. It's just needs to be freed from the rest of the cables coming from the Alarm box.

It turns out that there is even a way to feed it up to the windshield. After doing that, I was able to get over 30 feet (though it was parked in my garage which might have increased the range.) None the less, it is far better than having to be almost in the car to get it to work.

Steps to do this:
- Remove the panel cover (just two screws at the bottom that come out at an angle. Then you'll have to pull pretty hard on the bottom to get it to come out sometimes.)
- Remove the cable pull tie thing. (Black plastic thing that holds the clear plastic around the bundle of cables.)
- Pull the clear plastic far enough away so you can clearly see.
- Find the wire as described above. It was wrapped just outside the rest of the wires on my car.
- Pull the wire out of the taped up group, toward the box.
- Find a better way to mount it.

Extra steps to get it to the windshield:
- If you put your head really down and close to the openning, you should be able to see a light coming through from the windshield just to the right and in front of the speaker.
- I poked a hole in the side of the clear plastic so that it would have a shorter path to the front.
- Get something to grab the wire when it sticks out the top, like needle nose plyers.
- Take the wire and carefully thread it into the hole until you can see it come outside the other side.
- Grab it with the needle nose plyers
- Pull lightly on the cable to get it all the way through
- Then I taped it to my windshield mostly out of view. Once the cable gets set though, it's unlikely to move much, and I could probably have just let it dangle there.


I found this when, I went to try the previously mentioned solution, and I was having great trouble getting the wire harness unplugged from the alarm box. So, I was thinking of tapping into the wire a little further down the line. And I discovered it was wrapped just outside the other wires in the bundle. So, I traced the wire about 2 more inches to find that it ended. Then I performed the steps above.
I just completed this mod. I had to add to my antenna as it was only about 6.5 inches. I fed the wire about 37 inches up to the top and center of the windshield frame. I can arm the car consistenly from 110' from the back of the car And from arround the corner of the garage at 60' or if other cars are in the way then 60' also. I now have the range of my wifes corolla. This is awesome. A real pain to get unburried from the grey foam and the plastic bag; but it works beautifully. And it functions from inside the house and on the widows walk that is about 135' but since it is elevated I think that accounts for the additional distance gain. Again a great mod if you take the time to feed the antenna along the windshield frame. Robert
 

·
Registered
Joined
·
1,959 Posts
Very, very nice guys.

If I ever used my alarm I would be in the garage already freeing up the antenna wire.

My vote for best '06 mod and best bang for the buck!
 

·
Registered
Joined
·
1,265 Posts
I added to my alarm antenna and now have an incredible range (somewhere in the 200' line of sight range). I extended the antenna wire length by soldering on a piece of 24AWG insulated solid core wire. I then put a small piece of heat shrink over the solder joint and trimed the over all length to about 27.2 inches. I would have like to have extended the antenna fully out, but instead opted for a more simple installation by affixing it to the back of the side dash shroud. I used small pieces of aluminum foil duct tape to secure the wire to the plastic. I have always had great success with this type of tape in automotive applications continuing to adhere over the long term.

By the way, I didn't unplug the connector from the alarm. I just carefully pulled the antenna from the wrap.
 

Attachments

·
Registered
Joined
·
12 Posts
added weight

How much weight do you figure that metal tape added? Has there been any decline in the performance?

Sorry, I couldn't help myself......
 

·
Registered
Joined
·
201 Posts
Easy mod, but one word of caution. The aluminum panel that is along the bottom of the hole that you reach through to get to the alarm wire harness is guillotine sharp! Considering that you have to push a big chunck of foam out of the way and monkey with the harness, there's ample opportunity to cut oneself. I'd advise laying a cloth of some sort (wash cloth or folded t-shirt seems about right) along the aluminum edge at the bottom of the hole. On the plus side I now have a bandaid on the end of my middle finger to keep from bleeding all over pretty car. Gives me good reason to flip the bird! :coolnana:

Mike
 

·
Registered
Joined
·
1,504 Posts
add me too, lots of blood all over my garage floor, had to run out and buy some liquid bandaid to stop the bleeding!
 

·
Registered
Joined
·
1,265 Posts
Man... all these bleeders! :eek:
I am glad I have big hands... so I couldn't get them in there. I instead had to use a couple of long forceps to extract the antenna from the wrapping.
 
1 - 20 of 303 Posts
Top