Megane II Keycard repair instructions / Development

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Megane II Keycard repair instructions / Development

Postby tomalamix » Wed Jun 16, 2010 10:38 pm

Hello guys,

Well, now lets take care of business...this chitty (s instead of C of corse) keycard from Renault. The full story: when i bought the car I had 2 keycards, one only opened the doors and the other only started the car, so i had to walk around always with 2 keycards.

After this, 2 months ago the one that only started the card (this means that didnt give the message "Insert Card" on the dash) started to give me the message "Insert card" with the card on the slot, but during a few days i had to give some small taps on the card (when inserted) for the car recognize it. At this moment i thought: in a few days ill be screwed, the card will stop work, so i took my hands to work, opened the card that only unlocks the car. Now starts the electrical part and fortunately im a guy that can manage, measure and understand the philosophy of this keycards, (its similar to other manufactures but in a keycard format).

Instructions to open the card:

Where, i think that theres nothing on the web as good as this ones, it took me a lot of work and you may do this sticky if you want, pictures and instructions. Please do not dry out your pockets before you try this out and do it your self and exchange ideas with others:







Now its will take 1h-2h, its normal...

I've opened the card that only opens the doors and the coil (looks like a black coin) had a pin dried out from the PCB. Resolder it back and this card now starts my car without any problem, its totally functional!. Check this pictures as reference. The pictures below points out how to where the problem is and also explains how to solve the unlock/lock doors on your Megane:


Now, the development part, i opened the 2nd card and the problem where both, coil with dry solder from PCB and the contact from the battery dried out also. Well, just soldered them back and now it only opens and closes the door ok but still doesnt starts the car. This is extremely odd!. I've made some ohmic measurement on the pins of the coil. The measurement on the card that totally works one that works measure 95ohm (+-) and the one that doesnt work measure 56Kohm. This was a big difference! Then i've placed both cards, one at the time, near the card reader (the one on the car that i think that produces an electrical field that goes thought the coil. The coil, no matter if the card is ok or not it should produce some voltage, its pure physics) installed on the car and the card that works we can measure 12V on the 2 pins of the coil, and the other one doens't even move.

My theory: even if there is something burned out on the board the coil must "produce" 12V like the other, unless the problem is the coil it self. Following this idea i've substituted the coil with a card that i managed to arrange (a free hands model, see pictures below to understand the differences). The problem remains, no 12V peak on when i place the card on the card reader and, of coarse, "Insert card" message.

Model with hands free:


Model without hands free:


The previous ohmic measure comes from this 55,9Kohm resistor. I've soldered this components out and others and measure them outside the pcb. The results are on the picture, but now i have an other improvement: The ohmic measure of the coil outside the PCB should be something around 80-100 ohm (+-). If you cannot get that measure and get something like 59 Kohm or 90 Kohm probably you have a broken coil. The solution is to buy an other coil (i dont know where, but i saw them selling, just search with google, if you find it post it here) and replace it, or, like i did, take out the thin cooper wire until you discover the place where the wire is broken. It worked for me in both coils! Now i have 2 100% working keycards.

For thos who think its strange that with the coil ok ive measure 95 ohm and with the broken coil measured 55,9 Kohm its perfectly normal: the current goes through the "easiest" way, i.e., it goes through the path that gives minor resistance, the 95 ohm path and thats why the difference is so massive. In the broken coil card the "easiest" way is through the 55,9Kohm and on the working card the "easiest" way is through the coil resistance, 95 ohm.

For now the only think that it would be good to get is that someone with more knowledge than me in electronics confirms me that those SMD components are really condensers and confirm their values
One more thing I would appreciate is that some one gets some datasheet of this PCF7947AT (there are variants with /447 or other numbers in front instead of 447) to try to understand how they work and check if they are ok or not.


I think thats all we can do for now. If nothing of this tutorial works for you then you probably need to pay Renault big money... :banghead

Last edited by tomalamix on Mon Dec 29, 2014 12:06 pm, edited 2 times in total.

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Re: Megane II Keycard repair instructions / Development

Postby markren2004 » Thu Jun 17, 2010 10:55 am

great guide - i think it deserves to be a "sticky" - i'll add a link to it from the common issues sticky

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Re: Megane II Keycard repair instructions / Development

Postby ziik » Wed Oct 20, 2010 11:57 pm


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Re: Megane II Keycard repair instructions / Development

Postby Paddy » Thu Oct 21, 2010 12:15 am

This is excelent post. Regards.

I have made it a 'sticky' for future referance.


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Re: Megane II Keycard repair instructions / Development

Postby ChrisM » Wed Oct 27, 2010 11:16 am

Yee Gods
I have read this post 3 times now and it still makes no sense to me, it may as well be written in Klingon!
There are some very intelligent people out there, are there not!
The only bit I could manage is the cutting, after that, well; right over head I think the phrase is!!!!!! :conf
Great post, I think ;-)

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Re: Megane II Keycard repair instructions / Development

Postby kenster » Thu Dec 16, 2010 6:35 pm

Makes perfect sense to me, send me your keycard and ill solder it for 75quid :) save you 125!

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Re: Megane II Keycard repair instructions / Development

Postby AlexB » Sun May 29, 2011 12:18 pm

Hi guys,

This is my report on the key card repair. A couple of weeks ago the key failed and the spare one had to be used. Being curious, I opened the card to discover a manufacturing fault in the coil (the big black round object in the photographs above). One of pins was bent prior to assembly, thus causing undue stress on the wire. The wire is very thin, probably 0.08mm in diameter, and it gave up after 8 years in service. I soldered it back in place, and now everything works again.

The card: ordinary, not hands-free.
Board: ... dsfree.jpg
Symptoms: locking-unlocking works; when inserted in the reader - "INSERT CARD" message and no start; resistance measured on the coil while still on the board 95 kOhm (too high for any coil).
Repair: the coil is removed, the broken wire found and soldered back to the appropriate pin of the coil. Then, the coil is soldered back onto the board.

How to make the job easier:
1. Do not open the whole card - cut the plastic only on the three sides, then bend the halves of the shell to get access to the board. Trying to open it where the mechanical key is placed is difficult because of the glued seam hidden inside. Use a hot iron to free the battery contacts from the plastic (you'll see how to do it).
2. Examine the photographs above and take care to not damage the board.
3. Weld the plastic together with the soldering iron upon completion of repairs. Use a flat tip 3mm in diameter. Move it slowly along while keeping the halves of the key shell firmly pressed to each other. Move the iron in a kind of tiny circular motion trying to push melted plastic inside the gap. Try to keep the seam uniform and tidy.

General comment: although the key-card of Renault is significantly better designed than the latest keys of Ford, Alfa, BMW and MB (which are too large), the manufacturing quality is poor. When the car went in production, there was no reason to not use a standard smart card which we use with laptops for authentication. Just imagine how nice it would have been to be able to keep your card key in a pocket when surfing or swimming and configure the new one, if necessary, directly in your laptop, preferably with trusted open source tools...
(no, a different AlexB)

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Re: Megane II Keycard repair instructions / Development

Postby DonJuanito » Fri Jun 17, 2011 3:47 pm

Hi. I was searching the Net for a source for the Renault Remote Card coil when I found this thread.
As I repaired my second card, I whish to contribute this thread with a bit of technical information.

The coil is made of approximately 353 turns of 0.06mm diameter enameled copper wire over an air core of 12.5mm external diameter.
The selfic value of this coil is about 5.2mH, it's DC ohmic value is about 98 Ohms.

I didn't find a source for ready made coils, and it was finaly easier to buy a used remote to salvage the coil from it...

To anyone wishing to repair his remote, be very careful when opening the casing in the area where the battery is, as the coil is near the edge of the casing in this area (see the above pictures) and the tool used for opening it can easily slide towards the coil and cut it's bowels :(

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Re: Megane II Keycard repair instructions / Development

Postby steaky » Wed Aug 17, 2011 7:28 am

hi there
ive just had my key card repaired by a guy called phil who lives in saint helens at a very good price. My fault was it was going through batterys ding dong :banghead .
The doors were'nt opening and closeing. He stripped my card down fixed it ang it took him all of 45 mins well worth it and it saved me doing it and damageing the only card i have. i found him on ebay his firm is called P & D KEYS LTD As i said he is based at st helens about three mile off the east lancs ( A580 ) from haydock island. i will be going to him if i ever need to again, ive also told my friends about him. hope this helps anyone who may be unsure about openning ur card and having a go yourself. :D

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Re: Megane II Keycard repair instructions / Development

Postby Design_Dude » Sat Aug 27, 2011 9:20 pm

Hi all,

I fixed my keycard about a year ago (soldered the transmittor back on) and it worked grand.
Over the last while it has been getting worse at starting and card was very bendy so I bought a new case and took the pcb out of my old one.
I put it all together and it locks/unlocks but wont start at all now. I reopened the case and inspected the board.
I am now missing two small smds. The arrows point out the ones that are now missing...

Can anyone tell me are these resistors, caps or what?! And if so what rating should they be!

Thanks very much in advance!

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Re: Megane II Keycard repair instructions / Development

Postby max_cady » Sat Oct 29, 2011 1:18 pm

thank you.. ,,,,very helpful !!

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Re: Megane II Keycard repair instructions / Development

Postby Maidstone83 » Sun Feb 05, 2012 2:27 pm

Hi everyone I need so urgent help/advice.

I followed all the instructions on here and have changed the case for the key card. Since then, the card will not work, so I can't get in the car! And as it parked next to a wall, I can't use the key to open the door.

I have had a look at the board and noticed 1 part needed soldering which I have done but still nothing!!

Can you guys suggest anything? Is there anything I can try?



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Re: Megane II Keycard repair instructions / Development

Postby tomalamix » Thu Feb 16, 2012 5:26 pm

did you check for continuity when you press the unlock button? did you compare the pictures and your card board side by side to make sure everything is there?

which part did you soldered?

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Re: Megane II Keycard repair instructions / Development

Postby starspud » Thu Mar 08, 2012 8:59 pm

Hi, that 1st post was great. Thanks for taking the time to document it as you did.

I'm interested to see the differences between the handsfree card and the non-handsfree one, however the link that you've provided to the picture of the handsfree card doesn't work so i can't look.

The reason i ask is that my handsfree card doesn't work the car handsfree for some reason, and has to be put in the card reader to start the car (and the buttons on the door handles don't do anything either).

thanks in advance,

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Re: Megane II Keycard repair instructions / Development

Postby tomalamix » Wed Mar 28, 2012 2:47 pm

It doesnt work indeed...but you can see a handsfree model on the 1st picture of the thread, its lying down on the global map :). The differences are noticeable.

good luck

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