As I am sure you know, to start the car it is not necessary to have a battery in the card. The transponder is a RFI (radio frequency interference) device which responds to radio waves from an outside source. Your dustbin has one, to weigh your rubbish! Aeroplanes have them and these are given "squawk" codes to identify them to ATC. (Sorry if I am teaching my granny to suck eggs here.....!)
So the keycard does not need a battery to start the car. However the micro-circuitry does provide a link between the battery and the transponder. How do you think the card reader knows when your lithium battery is getting low? The transponder provides this information, even though it does not need the voltage to function.
I opened the case of the card very carefully and using a miniature soldering iron, checked all the joints for breakages or the electronic engineers' nightmare, dry joints. The former are visible, the latter are not. I could find no faults.
At the Renault dealer, the card was inserted in a reader and found to contain no information at all. I assumed the transponder had lost its memory, for whatever reason.
At this point, faced with paying Monsewer Renault 150 quid, I sent the card with £20 to keycardrepair.co.uk. somewhere in darkest Whales, sorry Wales! I had previously corresponded with Gary and expressed the opinion that I thought he would be unable to repair it, inviting him to prove me wrong. Here I am eating humble pie by the shovel load! The darned thing came back a few days later - WORKING!!!
The transponder had not lost its memory. All the info was still there! To understand this, it is necessary to grasp how the system works. See the attached photo and identify the large black coil at the bottom. This is the "receiving coil" which passes info to the transponder and back. If this is not connected then it follows that the transponder will not respond (sorry that's a bit obvious!) The coil is held by three connections. Number 1 is to hold it to the card. Numbers 2 and 3 provide the electrical connection. Sometimes these 2 connections breakaway from the PCB.
If you remove the coil, it will not affect the central locking, as I discovered.
So what was wrong with our coil? (Dave, at this point I must say that I may be the "voice of experience", but I still have a lot to learn!!) It appears that, despite using care, I caught the coil with the blade of Mr Stanley while opening the case and broke a wire!! Curses, but the coil is very close to the edge of the case. Well that is my excuse! But I am sure I checked the continuity of the coil windings with a meter between 2 and 3.....? Memory is not what it was...
Before I wrap up this "diabolical diatribe" I must mention that other members covered this "coil" aspect last year - Mondo9 and Ulrich100. How I wish I had read these beforehand but I was not then a member. I particularly liked Ulrich's method of heating the case to soften the adhesive holding the two parts together. That's a good one and well worth remembering.
Sorry to bore you but if you have card problems and don't fancy tackling them yourself, do get in touch with Gary at the above address. Without giving away any secrets, how does he know your card works before he sends it back since he cannot try it in the car itself? He checks the locking function using a frequency of 455mhz, and a card reader to interrogate the transponder. Seemples!
Sorry to bore you. Have you learned owt? Did you get to the end.....?
Cheers all, Mike
)it caries a compulsory excess of £25 for a claim to the amount of 5 a year to the value of £500 including vat. IMO, a steal if your car is out of warranty.