repairing broken W202 Key fob.

[anyweb]

Superb thread, thanks Anyweb

Just repaired my keyfob by resoldering on the switch after dropping it yesterday

Cheers!

nice to hear another key saved

 

[megah0]

This method works for w124 as well

 

[ferretavfc]

You are in deed a genius after lot's of ill gained advice about why my 1995 C220d Merc would not respond to the remote fob i stumbled on your site and your step by step guide to what could be wrong ie the inner workings of the fob becoming detached was indeed spot on, so after four small solder's it is fixed and at no expense excellent can't praise yo enough TA :

 

[davoC220]

if only id been here a year ago, both my fobs fell to bits when i went into a services for a coffee, fortunately my mates an auto spark and mobile too, waited 2 hrs for him to come out tho, and he did the same repair in 15 mins to both fobs, cost me £50 tho, but money well spent, probably saved me near £200 replacing them

 

[Ian Nexus]

Hi, here is a picture of the offending article, you can see the little black component that I found loose inside. Hope this helps to clarify the problem.

View attachment 6651

This little chip is a Philips fixed code RFID tag, these are used in immobiliser systems. It does not connect to the PCB in any way, they are fitted inside many key fobs.

Best Regards Ian

 

[Dec]

Using anywebs picture of the other side of the PCB it would seem their just isn’t any space other than in the illustration for something that size to fit, I don’t think it belongs in there at all, why it should exist is a mystery.
Any chance that the problem is simply dead batteries or incorrectly fitted batteries?

Dec

Hi Ian, that’s an interesting explanation to the above post, I was wondering how this chip turned up rederham’s key fob but not in other similar fobs, any idea what it actually dose or why it doesn’t seem to have to be connected to anything on the PCB.
We never did get any further feed back from rederham.

Dec

 

[television]

I managed to repair another DAS11 key today,,thats about 6 that I have fixed,,this one was a through plating hole failure

 

[Ian Nexus]

The RFID chip is a transponder here are details :-

http://www.codecard.lt/index.php?page=1&act=viewCat&catId=6

We used these to identify parts in a CBRN detection simulator at my old company.

Ian

 

[television]

The RFID chip is a transponder here are details :-

http://www.codecard.lt/index.php?page=1&act=viewCat&catId=6

We used these to identify parts in a CBRN detection simulator at my old company.

Ian

Thanks Ian nice to know what that was

 

[Dec]

Ian, thanks for that, would its absence from a key fob cause that key fob not to work, as in the case of my previous post?

Dec

 

[television]

Ian, thanks for that, would its absence from a key fob cause that key fob not to work, as in the case of my previous post?

Dec

Yes it would not work without it. they are not used in the later keys

 

[Dec]

So I should have one in mine, I have had mine apart before but never noticed it, must check again, this is a whole new can of worms as a possible fault issue.

Dec

 

[television]

So I should have one in mine, I have had mine apart before but never noticed it, must check again, this is a whole new can of worms as a possible fault issue.

Dec

Dec the are many variants on these keys,,I have seen 10 different versions of the later keys,,though I have only fixed 2 of the flip out keys,,one for sure did not have that part in it

 

[Miffy]

the RF chip is just the same device as put in shop security systems and door control systems, a magnetic field excites electrons in a coil and powers the chip to broadcast a string, from 16bits to god knows how many these days, we use 40bit cards for our door entry readers

 

[Sean Ng]

Hi Guys

It seems to me that I have the same key fob problem - broken 4-leg rectangular component.

Before I start soldering the legs, I have done a quick test but only finds that there is no red light flashed out.

The way I carry out the test is:
(1) Insert working batteries properly (fastened with tape), making sure there is contact;
(2) Hold the component back on the PCB by finger; and
(3) At the same time, press the button on the top of the component.

I wonder if I have done anything wrong in my test. Should it work by just simply soldering the legs? Hope you can help.


Regards
Sean Ng

 

[television]

Buttons with 4 legs have 2 straight through contacts so it must be soldered on.

The LED means nothing for the working of the key,only holding in front of a digital camera will show that it is working

 

[Sean Ng]

Hi Malcolm

Thank you for your advice. Will solder it and let you know the outcome.

Regards
Sean Ng

 

[megah0]

I must be super clumsy

fixed the key again today, however one of the legs on the switch has broken off now, I managed to get it working by carefully (oh so carefully) building up solder to the tiny bit of leg that remains. However if I drop it again (likely) I don't think it'll be repairable again.

Where can I get a replacement switch from? Are they common items?

 

[television]

I must be super clumsy

fixed the key again today, however one of the legs on the switch has broken off now, I managed to get it working by carefully (oh so carefully) building up solder to the tiny bit of leg that remains. However if I drop it again (likely) I don't think it'll be repairable again.

Where can I get a replacement switch from? Are they common items?

Yes they are common,,,what is the size of it L x W

 

[megah0]

Yes they are common,,,what is the size of it L x W

it is 6mm x 6mm.