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need help identifying mod by previous owner

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Hi everyone,

So I've had a 2004 C4S for a couple of years, and I've always wondered about a mod done by the previous owner. I was hoping the collective expertise here at RennTech might be able to shed some light on it.

There is a small switch of some kind on the carpeted side of the upper center console by the driver's right knee (two pictures attached). The switch is wired to a tiny speaker hidden in the A pillar trim to the left of the driver's head (pulled down from the trim in the attached picture). There are two moving parts on the switch. The center knob controls the volume on the speaker. The outer ring is a dial that rotates one click in either direction from center. If the outer ring is rotated in either direction, the speaker makes a sound like a radar detector turning on, and then beeps once every five seconds. There is no obvious difference between the clockwise and counterclockwise settings. When the outer ring is clicked to the center, the speaker is silent, and whatever it is appears to be off.

Other than these two things I don't have any visual evidence (for example, I can't find a detector hidden anywhere). Any ideas? Eventually I will get curious enough to tear everything apart and follow the wires, but I was hoping for suggestions first. Sorry for the poor cellphone picture quality. Thank you in advance for any thoughts.





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I had a similiar switch on my car when I purchased it and found out that it was indeed for a radar detector. Can't remember the brand of the top of my head, but if you turn the knob in either direction from the center position it switches the radar from street driving to highway driving. When the switch is in the middle then the radar is turned off. The difference between highway driving and street driving, is that on the street you get more intereference on the radar and it signals more frequently, therefore you want to make sure that you put the radar in street mode when driving on the streets, so you don't get the annoying noise all of the time. My radar transceiver unit was mounted inside my front bumper, so you might want to check there.

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it is from a K40 undetectable model. usually has front and rear sensors

do you have a front tag frame? if so does any wires go to it or can you see a small box in the front grill?

should have a small box mounted in the rear bumper area also

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  • 9 months later...

Hey -- I have an 03 996 tt and I have the exact same knob in my car -- I also cant figure out how exactly it works. Turn the outer ring one way and there is a light that turns yellow, turn it the other way and the light is green. Probably signifying the difference between city and highway but which is which? I have no idea. Also, the thing beeps all the time when it is on and I wish it would be quiet and alarm only if there is radar etc. Do you have any idea how good this model is or which model it actually is?

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i have one on my 2003 C4S. This is the manual for mine...

K40 1000/2000 link

Works great if you adjust appropriately. Although, i haven't been able to stop it from pinging (in 'city' mode) when i blow by the local 7-Eleven store - the unit is sensitive to a number of commercial motion detectors used for doorways.

But it's definitely saved me more than a few times, especially when approaching those signs that display your speed in construction or safety zones, and - wouldn't you know it? - there's a highway patrol or local cop out of sight around the corner;)

(Loren - hope posting the link isn't an infraction of the posting rules?)

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Yes, its a radar detector and a great one at that. I've go the K40/2000 system installed and it works fabulous. What else can I say? I also agree that even in city mode, its a little too senstitive but that better than the other option. Volume level could go lower as well.


2000 C4 6 speed

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I to have wondered about this switch and couldn't find help in the owners manual. So now I've turned it on and the lights flash and it carries on like a detector, but no sound. Our car is a cab, so does anyone know where they hid the speakers?

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I also have the K40 on my '03 C4. Has saved me a couple of times. It has radar detectors mounted in the front under the bumper cover and in the rear in back of the left brake light module. It also has the laser jammer in the front which is a small box mounted under the front license plate with a row of LEDs facing forward. If you get a laser hit it turns on the LEDs to swamp the return signal to the laser gun. Overall a very nice system.

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