Broken Keyfobs

Hi All

I have engineered a simple fix to the common "keyfob drains battery in
48 hours" problem that affects at least a lot of 306 owners and
perhaps owners of other models.

I discovered that an afflicted keyfob was drawing 4mA with no buttons
pressed hence the horrendous battery drain! There is a electronic fix
- modifying the button switch connections to only connect the battery
to the circuit when the button is pressed - hence defeating the failed
component and associated battery drain - works a treat on my 97 DTurbo
(2 button fob). The only downside is that to activate the second
button - you have to press the first one first. I have never used the
secondary button so it isnt an issue to me!

I hereby offer to mod peoples fobs for 25 notes - Peugeot charge about
80 quid for a new fob. You'd not have any recoding to be done or
anything - would you be interested? If so reply and we can negotiate
offline..

Raz.

 

second button (ir type) arms alarm and sets deadlocks so why pray tell
aint you using it (cos its worth it for the deadlocks at least)

 

I am working on a complete solution to enable normal second button
operation.. Will post progress on this early next week.

Raz.

ps. My car doesn't have an alarm and you're right I should be using
the deadlocks but have never bothered..

 

btw pug reckoned it was static causing probs with the cmos chip inside
is this true then?

 

It would certainly appear one of the ICs has failed. Connecting the
fob up to a power supply showed that it was pulling 4mA with no button
pressed! However the failure does not prevent the fob from operating -
as you know they work fine whilst the battery lasts. This is why
actually switching in the battery with the button press is an
effective solution..

 

Hi Jeff,

Oh, the old CMOS thyristor-lock side effect. I thought it was just old
stuff, and that we got rid of this annoyance with more recent chips.
Usual solution is to use two diodes : 1 between input & VDD, the other
between input & VSS. For this use (low power) I'd recommend signal diodes
like 1n4148 (possibly available as SMD).