rf transponder rings sensitivity issues

experienced installers.   

i have been gradually finding more sensative and inconsistant problems w/ transponder boxes and rings.  i prefer to use them do to cost and speed.  i deal primarily w/ bypasskit boxes or build my own w/ a relay.    

the main thing is that i see more and more cars that work fine right away come back,,,,,,but not right away.    ex.   i had 2 honda odyssy vans come back this week(and we are super busy so it sucks)  that i have done months ago on one and 2 yrs ago on the other.   one i wrapped my own key and used a relay and the other i used a box w/ one of the new "sticky ring" loops w/ the exposes windings.   

why are they all of the sudden deciding to be picky..    neither of them moved a mm from inital install.        obiviously if you do a ford when its 70 degrees and the next morning its 10 degrees it will show up quickly if your not in the correct placement.    but when that same car comes back 2 yrs and nothing has changed makes for an irritating day.   especially when the customer is wized and of course you cant get it to not start in the shop and it has to be w/ in 3 inches and  starts every time.   

any tricks ...i am pretty experienced, own a shop and do alot of cars so please no "basic" comments like try to move the ring.

ahh yes very irritating especially on some cars *cough* chrysler *cough*. it's hard to say that it hasnt moved if you havnt seen it in 2 years but i know what your saying. the problem is the ring (depending on the sensitivity of the transponder system) for the most part needs to be as close as possible to the front of the cylinder.  it only needs to move like an 1/8 of an inch back sometimes to lose connection. as for the tricks part, i put like 4 little pieces of dum dum(sticky tac or whatever you want to call it) around the cylinder to help hold the ring in place. then wrap it as tight as possible and use a wire tie to keep it tight. usually works for me with no problems. i find those "stick on" ones not very useful, i never use them but i seen cars come from other shops before and i guess in the cold, they lose their stickiness and just move.

oh yea...if that doesnt work try moving the ring haha 

when i use a raw wire or non sticky ring,  i usually even hot glue the damn thing in place..    i swear they become more sensitve or the chips get alittle less strength in sending or something, and CONVIENENTLY the problems get worse in the cold.    i like the sticky rings alot for fords.. seem to have good luck w/ cars that came back transponder issues,  i chop the wires up there and add my sticky ring and its usually much improved.    also have had one chrysler and multiple vw's that the only thing reliable was a ring on the outside of the shroud....VISIBLE to customer..  i just  made them black w/ tape and the customers never noticed..  sounds ghetto i realize but no probs.

what brand of boxes do you use ?    the funny thing is that i have had a few cars that wont catch the signal if i am using a transponder box  but will work w/ a 95cent relay and an 6 cent piece of wire..   the $15 box is no good,  but my rig job does the trick.  

this is the first time i have done this... just yesterday i did an 03 audi A8.    its my car and i have 2 switchblade keys.   i can get them to work w/ a relay and wire but often sucks for reliabiltiy... as per a previous post i used a 556u?   which i have in the bypasskit  version..i think the tbkv off the top of my head.. the one w/ the big rubber ring style coil and 3 black wires in the plug goin to the ring side.    anyways thanks to the post that let me know that would work by integrating into only one side of the transponder  wires.   everything was cool w/ the exception that my key wouldnt fit in the box.   i didn't really want to hack it apart and i didn't want to pay for/wait for a new smaller basic key.   i took a piece of wire and wrapped the hell out of the portion of the key w/ rf,  then picked a jumper setting on the key winding selector and soldered the ends or my homemade wrap to the circuit board..  works good.   the key was to bulky allow the box to fit back together correctly.  i did some creative hacking on it and then taped it together as close as it would get.. not the prettiest, but effective..

i wasn't aware the you just had to interupt one wire on german cars.    i.e introducing your new wrap wires in line w/ only one of the two factory wires. 

in bmws i have removed the factory rf ring, relocated, taped a key in the middle.. and then this is critical!  use a relay to open one of the wires when the car is not on.. the ignition triggers the relay to close the loop and sense the key.   if you dont break it w/ key off, doors might not lock, dinger is funny, ect. 

thanks for the intelligent replys guys

OK I don't know if it will help but let see;

Copper is the best RF transmitter/receiver except if you can afford Gold!
Multiple strands are of no use in RF not to say bad

Solid telephone wires we find in walls are the cheapest one strand almost pure copper wires. Youpull one wire out to cut the envelope and you have now 4 wires to create your own best ever transponder loop.

Smaller is the wire and more loop you will be required to do (usually with this type of wire 4 to 6 loops in fron of the immo antenna are giving the best results.

The loops around the key will not permit proper RF field dissipation to the transponder unless they are all at one end of the key.

My recommendation, make the loop all over the key head but leave 3/32" of distance between each loop.

Many boxes are using the cheapest components you can find in the field. the distributors are always searching for a cheaper box and obviously failure occurs. Use a good putter and brumfield 40 amp, why not, anyway the coil will not disturb the RF as it's on DC, no frequency there.... Minus 65 the relay will still click.

A 1.5K resistor squeezed between the transponder and your loop will generate enough heat to avoid a transponder failure even at -55c. Make sure the resistor is powered OFF when ignition is ON (one end of the resistor to 12vdc, the other to 12ACC) to avoid amplifying the noise generated by the current flowing in the resistor when the transponder challenge is engaged by the immobilizer module.

Another way to make a transponder when you are desperate;

Wrap a very thight coil to cover the entire key head
Stick the key head along the immobilizer antenna in a location where you obtain your best accuracy.
When you close the end of the RF loop (touching both ends of your looped wire togetter) you will create a RF shiled, the transponder will not be able to communicate with the immobilizer anymore, open the loop to remote start.

The loops around the key will not permit proper RF field dissipation to the transponder unless they are all at one end of the key.

I should have said: Thight loops around the key will not permit proper RF field dissipation to the transponder unless they are all at one end of the key.

racing_bidule wrote:

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A 1.5K resistor squeezed between the transponder and your loop will generate enough heat to avoid a transponder failure even at -55c. Make sure the resistor is powered OFF when ignition is ON (one end of the resistor to 12vdc, the other to 12ACC) to avoid amplifying the noise generated by the current flowing in the resistor when the transponder challenge is engaged by the immobilizer module.

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explain that to me, where does the resistor go...in line with which pins to generate heat.....im confused here I guess, I understand the theory just not the application

OK, the whole idea is that transponders are getting less sensitive when they freeze.

If you connect one end of a resistor to 12 Volts and the other end to Ground, current flowing true the resistor will generate heat. Providing that small amount of heat to your transponder will be sufficient to prevent it from freezing. So a 0.05$ resistor can save you come backs related to sensitivity issues especially where the climate is extremely cold.

Transponder will perform well to a temperature above -25C, below this temperature the component is not rated to perform anymore (in multiple brands) If you want to avoid it reaching this temperature, install a electric heater (a resistor).

Now also, cheap transistors loose a lot of gain when they are submited to very cold temperature. If you buy cheap modules, you buy cheap transistors. Pay for military grade component, it's worth it.