Remote key fob: battery replacement: alert

Muttley

Catch that diesel!
Mar 17, 2006
4,987
31
North Kent
Not sure if this is the right section so I'll post here and link from the Leon and Toledo forums.

My remote keyfob (standard non-folding key, Toledo 2004) ran out of battery today. At least, I think that's what the constantly-flashing LED on the fob was trying to tell me - that and the fact that it wouldn't work the locks any more.

Okay, not a big problem, change the battery. Well, after having got inside without wrecking the fob (not as simple as it sounds - three hands would definitely help) I did so. Single CR2032, as expected. Buried in a well in the non-key half of the fob - difficult to get out and also to get the new one in.

Reassemble key - no LED flash from the fob at all when the buttons are pushed. Not what I expected. Disassemble key again - find that the LED flashes when the fob is half-together but not when it's fully reassembled. Now that's really odd.

After some mucking about, found that the long contact for the middle of the negative pole (the face of the button: the positive pole is the cup) had been bent just enough that it wasn't making good contact with the cell. When the key was half-assembled, the contact was being pushed down onto the cell, but when it was all fully together there was no force pushing the contact down and it lifted free of the cell.

Well, thank you, nameless VAG designer. Removed the contact (it's held into the key body by a tag on the upright part), bent it so that it had more spring force down onto the cell, reassembled and I now have reliable remote function again.

So if you replace your remote fob battery and the LED goes on strike, have a look at the contacts. You might save yourself the cost of a new key and the hassel of coding it, which is probably more than £100 in these enlightened times.
 
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Muttley

Catch that diesel!
Mar 17, 2006
4,987
31
North Kent
I thought after I'd written the above, this really needs pictures.

Keyfob from overhead. Button cell encircled by plastic holder in the bottom half of the fob, contacts rising up either side to make contact with the circuit board in the top half.

Fob-overhead.jpg



Keyfob from one side, to give a better idea of the geometry of the contacts

fob-oblique.jpg



Diagrams showing just what went wrong: getting the button cell out is not easy, and in doing so, or when putting the new one in, I'd bent the top contact upwards.

Keycellcontacts.jpg


This would be so easy to fix in the design stage: the contacts don't need the S-curve where the circuit board sits, the keyfob is held together by strong plastic tabs and the contacts could be made with simple flat portions to wipe the circuit board edges.

Simplicate and add lightness :)
 
Last edited:

Chris0408

Guest
Central locking problem on my LCR when using the remote only 2 rear doors lock is this the hole central locking or just a couple of sticky locks? Cheers :)
 

Sean886

Active Member
May 15, 2014
371
0
Ive only got one key and the fob isnt working. Having to lock and unlock with the key in the hole (giggidy) any idea on how to solve this?
 

reckord

Active Member
Sep 24, 2014
28
0
Hope this thread comes in handy as i have a factory alarm thats testing me lately
My fob wont work everytime really temperamental,
So when it goes off i struggle to de-activate the thing
:mad:
 

reckord

Active Member
Sep 24, 2014
28
0
Hope this thread comes in handy as i have a factory alarm thats testing me lately.
My fob wont work everytime really temperamental,
So when it goes off i struggle to de-activate the thing
:mad:
 

Kruga

Active Member
Nov 1, 2014
42
0
Cheshire
My flip key battery died few days ago the alarm is starting to get annoying.. i have to lock it manually now and sometimes the alarm just goes off after a few seconds so i have to unlock it manually and start the car up the turn the car off and lock it again then it locks and no alarm :/
 
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