Mercedes w202 key and remote test and repair. battery test

How to easily test and repair an older switchblade style Mercedes w202 and similar key/remote and batteries. you may need to reset the key to be recognized by your car once this is finished...simply point the remote at the door unlock sensor and push the button twice,,then insert the key in the ignition and turn to the first position...the key should now be re-set to be recognized by your car follow me on twitter / fupabox

[@nicolaipalma5941]

I just wanted to thank you for all of your video repairs on the W202 model. You have saved me many times, not including thousands of dollars.

[@fupabox]

Excellent..that's what it's all about.. glad they helped :)

[@pieterchristiaens8600]

Thanks a lot for this video! My key fell on and pieces went everywhere, now it's back together and it's more solid than before. Thanks for teaching this!

[@martyegerhardt]

Thank you for posting this video! My issues was that the fob had come apart. The spring and button had come out and I had no clue as to how to put it back together so I had a floppy key for a couple days. THANK YOU!!!

[@donnarandall4668]

OMG!!!! I am soooo glad I read further down in your replies. This morning I came out and found my dors would not lock/unlock on my 1997 C230. I read the manual previously when I received the car for Christmas and TOTALLY forgot about "Valet Mode." I don't know how but after trying everything, then reading about valet mode in your replies....lo and behold that's what it was!!!! Thank you so much. Your videos are awesome!!! Here's a big hug and kiss on the cheek

[@fupabox]

lol... glad it helped

[@clarkfraley5682]

I really appreciate all your R129 videos, this one most recently. I took my 96' SL500 in for a mixed bag of service last week. Among other things, a non-working remote. I replaced the batteries and got the led to flash but no IR. The dealer said I had a bad remote and it couldn't be replaced. I watched this video and pulled the remote apart. I reflowed the solder joints on the microswitch and BOOM, working again. Now I have to tackle fixing the motorized antenna, replacing the e-break lever. replacing the windshield washer pump, and rebuilding or send off the convertible top cylinders...We'll get there.

[@clarkfraley5682]

Well, this one is not technically an R129 video but the same remote :)

[@fupabox]

You will get it done...and you'll love the car

[@geepas4888]

Worked for me!! I just simply did what you said in your description when I replaced the battery. Point twice at sensor... Open switch. And voila... It's working. Thanks a million!!!

[@EXOTIQ786]

Thanx for the GREAT VIDEO! Did this on saturday night at 11:56, made my old key look brand new, it was all bent out of shape.

[@sabamadaki8747]

Thank you so much for this knowledge 🙏🏾, a multitude of chaotic events were about to unravel if I hadn’t seen this video.

[@MrAufei]

Thank you very much for this. I have a 1994 Mercedes 280E and on the weekend. (My model has the flashing lights oln the drivers door handle) I dropped my remote and the battery compartment opened. I put the batteries back in but the remote wouldn't work. The cost of a replacement from Germany is prohibitive and I eventually came upon this thread. I checked the remote with the camera and the red light and flashing light was working. I then followed you instructions and the key reset first time. Thanks again

[@fupabox]

glad it helped :)

[@Rimrock300]

I've got the same key for my W124 '95. I was away from home visiting a friend, and my key was dead when I wanted to go home..I knew about the red light that shows if the battery is working or not, and it was not present, naturally. Changed the batteries to some new ones, but still no red light. Found this video and got the idea to open the key to look for some broken connections, and discovered that the main button on the card had come loose, all the 4 legs. Got someone to come over with a soldering iron and I got the thing connected again. Bingo! Could get my dear Benz started and get back home;) Thanks for posting the video:)

[@fupabox]

excellent ..glad it helped

[@mazb6t]

I've got to repair the remote locking on my boss' 93/94 Merc SL and this info will surely help. Good vid man.

[@theresastark6461]

Just saw your video. Your information was right on! We were able to get the remotes to work on a used Mercedes we just bought. Your information on resetting the key was also most helpful. Thank you so much!

[@fupabox]

very welcome

[@ur.cristiiano.o]

bro u saved my life i love u

[@pin22pin]

You Sir are a life saver and no you are not brain dead. Thank You for the video.

[@dianneashcroft5216]

that camera/battery test was REALLY useful too!

[@robertsalstrom9682]

I did not see anything more through the camera than I saw with the naked eye...just the infrared light-no pulsing white lights.

[@BenAaronTube]

AMAZING! i honestly didnt expect this to work but it did. THANK YOU SO MUCH. Im such a rookie at this kinda stuff and you just saved me 200+ dollars. AWESOME vid man. :)

[@mariolaraia5699]

Great video. Easy to understand the problem and the solution. THANK YOU!

[@yuri_yabi]

Thanks for your reply! Finally got it apart, soldering as we speak, hope this does the trick as both my keys don't work

[@fouadmassoud8874]

Thanx man it was really helpful and the problem was with the botton but i fixed it and it works now

[@mariellemartin5910]

Thanks for to tip. It was my problem. Working now!

[@peteraudley4671]

My problem was same as previous comment by marty. I'd bought a replacement case without instructions and didn't know you had to twist and spring load the king. Also a quick mention the chip in mine was loose and fell out without realising . I spent two days figuring it out and was lucky to find it again. So be careful with the chip or it won't start the car !?👍

[@fupabox]

yes , you are dead right .. the chip can be loose and go missing

[@Rogerrgb]

Hi, I will try it an I'll give you an update!, Thank You very much for you answer I really appreciate it, we do need more people like you sr.

[@sorrysirmygunisoneba]

Great video, never knew you could do that thing with the infared light and the camera.

[@tourri]

Great help for 96er 200C station! Thank you from MercTown :-)

[@Chanenersys]

Thanks a lot. This is a great video. Now I only need to see how to synchronise a new transmitter to the car!

[@fupabox]

sitting in the drivers seat point the remote at the rear view mirror and push the unlock button on the remote..when the light on the mirror flashes green insert the key in the ignition and start within 10 seconds

[@Chanenersys]

***** Thanks, shall try!

[@lawrencepellegrini2687]

Just wonderful presentation of the kind & wind assembly of the switchblade, did my R129 so many times , I lost the positive battery connection , maybe you can verify, I was told not long ago that Mercedes dealers are no longer offering the key replacement for Too much money,,, thanks

[@fupabox]

The dealer may be still able to get them . Not 100% sure . I haven't called them for one in quite a few years . If you can find a used one you just need to swap in your pill sized transponder chip that sits in your key case by the metal key blade . Thats the thing that pairs the key with your ignition . The rest of the guts can be used and the new/used key case can be paired to your car .

[@alfamontreal100]

Thanks. I'll see how it goes now that the key is working. So far so good. It didn't cut out yet.

[@yuri_yabi]

I was wondering how you got rid of the glue that holds the key together. I'm scared of breaking my Key while opening it. All tips are very welcome

[@watermelon3566]

Hi, I got a w202 c280. the red and green light flashing alternatively when i try to start the car. The starter will turn but not run. i had change the fob key battery. I try to reset the remote with sit in car, press the remote (pointing to the rear mirror) lock then unlock and try to start the car within 15 second. With not luck, the red and green light still flashing alternatively. I can use the remote to lock and unlock the door. Your help is very much needed. Many thank in advance.

[@pieterc83]

Thanks for the tip on reseting the key!

[@mehmetdogu384]

man is different class

[@watermelon3566]

Hi, Just try out the new battery with disconnect more than 10 minute. Pointing to the rear mirror. Press lock and unlock once. The car manage to start and run but it stop after around 1 minute. Then the red and green led flashing alternatively again. :(. Then try the lock unlock sequence again and try to start again. The starter turn but engine still don't wanna run. After a few try the red and green led flashing alternatively again.

[@watermelon3566]

Hi, My fob is similar to the one you show in the video clip. with one button only, hence, i assume your comment to press the lock/unlock button on the remote once is to press the fob button twice.

[@RaideRRazorback]

Thank you very much! good video! i just fix my 2 key in 10 minutes!

[@watermelon3566]

Hi, By using the phone camera trick, I can see the ultraviolet light and infrared flash once if I press and hold the button more than 5 second.

[@watermelon3566]

Hi, Thank you very much for the comment. What will happen if ovp or fuel pump delay fault? Can it be the genuine fob fault?

[@sacredsarah5409]

Hey bro thank you very much you helped me so much thank you God bless you

[@peterhh369]

Hello mate could you please do one video for the newer type key as well? You know the full plastic with the hidden switch blade so called NEC key?

[@CABLEGUYJAY100]

Thanks bro! Second thing I fixed for free.

[@KazuyaMiikama]

Hi, fupa. I've watched your videos for a while, since it refers to w210 chassis as well. Mostly. I've had problems with my w210 (1996) switch key from the day one. It opens and closes the doors whenever it feels like it. Batteries are brand new and the right size to be exact. I did the battery test with my camera and the light is doing the exact same thing as yours. It should flash repeadetly, right? Mine doesn't turn on the light at all or it stays on and won't shut off no matter what I do... Pretty weird.. Do you think the solders on the button itself are bad?

[@fupabox]

+etu keno That is the most likely problem... I would try re-soldering them

[@KazuyaMiikama]

I'll have my friend with more electornics experience do that to be sure. I'll let you know if it worked. Thanks!

[@KazuyaMiikama]

+etu keno I did some further testing and it turns out the casing of they key doesn't seal the connection to batteries. I cut out a small piece of smoking filter and placed it between the battery connector "leg" and casing. Works flawless now. Just my two cents for people experiencing same sort of issue. Mine was as cheap and simple as that.

[@fupabox]

etu keno good info.. excellent :)

[@MrCYCLESMITH]

Beware of some of the aftermarket key fob shells for the W202. The internal circuit board out of mine would not fit one type even though they looked identical on the outside. The inside cut patterns differ slightly. If you have a CE on the back of your fob do not get one that does not have the CE. My circuit board (1997 C230) would not fit an Ebay shell. Had to try a few types.

[@fupabox]

good info..I must have lucked out since mine fit fine..It came from a seller in France

[@garrettdodson6110]

My key keep draining batteries I think. I can put new batteries in and it reprogram it to the car, it will work for a day and then when I click the button the car no longer responds. What could cause that?

[@delorean831]

If by a chance you see this comment, did you ever figure out what causes the IR to fail in the always on like the first key you show?

[@ivandiyanto1]

Great vid bro.. Would you continue with resync/reset key vid? Mine still not worked it out.. Thanks

[@kchilz32]

@fupabox That's what I was afraid of. Thanks for the reply you rock.

[@steviekakez]

thanks for this video, learn alot, too bad my case is other, my remote is with slide fisical key and is the plastic that sticks on the ignition hole.

[@watermelon3566]

Hi, Update on my issue. After send to workshop, their finding for the flashing light is to reset it via computer. With another fault is the fuel pump. The fuel meter also not accurate after the workk they done they are going to replace the sensor inside the fuel tank.

[@Binhxz]

i'll try it at home,, big thanx bro,, :)

[@fabiodias4668]

My key when battery changed keep the infra red light always on, do you know by where can I check for a circuit closure?

[@chombito1]

Hi and thanx a lot for a very useful video. I have one question, where is the signal receiver located, is it exactly in the mirror where there are green/red light flashing?

[@watermelon3566]

Hi, Remote battery changed, got it from my Mercedes agent. Still can't. Might change my car battery later because tries too many times it sound low power now. The green and red led at rearview mirror flashing with 2 patterns, both led flashing at the same time and both led flashing alternatively. Mine is both led flashing alternatively. Thanks again for your fast reply.

[@neilwilliams5814]

What do I do next if this doesn't work?Awesome video. Thanks.

[@fupabox]

if you have checked all the soldered connections and the buttons ,and there is still no visible light (assuming the batteries are good) the key may need to be replaced

[@BasementKilling]

Fupabox, what if the red casing that covers the infared bulb is missing? There is no red l.e.d. or infared beam emitting from the fob also

[@Rogerrgb]

Hi, Thank you for the video it's really awesome, about a video with the faulty key with the light on you have do you know something about it or any video link that explain how to fix it? mine keep the UV light on just like that one

[@watermelon3566]

Hi, I tried pointing the remote to the driver door handle with green and red led but not respond from the car, i means the door will not lock and unlock. i need to point it to the rear mirror receiver to lock and unlock the door. I try again to start the car and the starter will turn but still not run. After a few tries the red and green led at rear mirror flashing alternatively again.

[@jimpeanut6697]

If i send you my key could you repair it? How much would you charge. I need a new lock button because its missing, and the contact point for the battery thats it

[@MatCendana]

Looks like the W210 and W202 have different keys. Yours is much easier to open while there's a procedure to follow with the former before one could get to the batteries. But the plus point is that the W210's key is unlikely to suddenly pop open. I presume the batteries for both models are similar - Lithium CR 2025...?

[@fupabox]

yes they should all be cr2025

[@vjrains]

Tried it. I think the led is bad. Gets a voltage reading at the led connection but no infra flashes. Not to mention mine had a couple other parts. Looks like a little magnetic square with a white plastic holder that goes in before the circuit board. Assuming that is another added security feature that reads at the ignition to the key to actually start the vehicle. Make sure you watch how the peices fall out. My switchblade key is for a 99 mercedes sl500...

[@watermelon3566]

Hi, If I point first to door handle and press, no respond from the car, the door still lock. Is there any sensor at the door handle? Possible mine is faulty because can't unlock the door by pointing fob to the handle and press once.

[@watermelon3566]

Hi, Not yet. Will try and post with the result

[@MichaelWilliams-fc2fu]

thanks dude.helped me

[@pinno713]

Thank you.

[@MegaVDubMan]

Great video!

[@keithjeffs2764]

if you look closely the original mercedes key has a pin through it when key is half ejected, why not just switch the actual key post with the new key remote? or also a little customisation of plastic (shaving possibly with dremmel will allow to switch also)

[@fupabox]

actually yes I think you can press that little pin out...

[@MZ69123]

1997 C230 base 4 cyl for the climate control system readouts. Havent done it so dont know which ones just want to be prepared. Ty

[@mariolaraia5699]

Is there a fix for the driver's heated seat that no longer turns on?

[@alfamontreal100]

Worked for me. Thanks so much. What wattage of soldering iron do you recommend for car circuit board work?

[@fupabox]

glad it worked..good question.. I use a variable temp.soldering iron.. adjustable to 60 watts..I'll ask my electronics genius friend if there is a wattage that is most suitable for car electronics

[@dianneashcroft5216]

that was really helpful video, thanks!!!

[@fupabox]

glad it helped

[@anassdkh]

hey your video is so helpfull so , i took my key to repair and the IR light is working but not opening the car :( what should i do ?

[@nielssen21]

Hi. I have simular key on my 95` W124 E220. I have the same problem with the key remote buttom not working. Is it the same reset sequense on this? Daniel, Norway.

[@gabrielzanandrea]

I need to buy a new one, do you know where I can find it? And sorry I commented in on of the other videos about it, i didn't know you had a video about it

[@beauhatman4395]

first thing YOU need to do is figure out how the "focus" on your camera works...... "infra red", BTW

[@ianrocks3061]

The only thing you failed to mention up in the corner of your original fob is a tiny chip that you must transfer it’s inside the old fob and anyone following your instructions will throw away their old plastic covers away and their car will never start !

[@Binhxz]

i lost my key spring,, wondering what should i do now,, it wont flip like it use to be now,, :'(

[@MegaMusical10]

Thank you for sharing!

[@watermelon3566]

Hi, How long do I need to disconnect the car battery for it to reset?

[@TeamMac69]

Is it possible to put a new key blade onto a replacement fob?

[@ScrapMetalToCash]

THNX MAN U ARE GR8 I chech out my remote and found that the IR LED legs were broken, fixed it THNX 2 U

[@farooqahmad7390]

can you tell me from where can I buy whole new set remote and chip and how can I set program on new set thanks

[@ANDERZENAMG]

Hi Fupabox, long time subscriber. I know this is an old video but, do you know how the mercedes keys with no red see through port operate? I have a 2000 ML55 and the key will start and unlock the car manually but will not unlock and lock with the remote. I have changed the batteries, cleaned the contact points and aligned everything correctly. Any thoughts on what it could be? Much appreciated!

[@fupabox]

There is an antenna attached to the AAM module under the hood . It attaches to the fuse panel . Check that the antenna is screwed in all the way . Looks like a cable coax connector . I think it’s shown in my AAM replacement video .

[@ANDERZENAMG]

fupabox thank you! I’ll give that a shot and update.

[@45stephani]

I need help asap my cars locked and it won't let me start it because the anti theft system but I bought new battery's the car unlocks and locks but it still says its getting robed

[@ajman52]

great tip buddy!!

[@brautus]

Hey again fupabox. What type of batteries are inside this casing? cr2025?

[@fupabox]

+Braut The Gaut on the switchblade key it should be a 2025 from the factory.. a 2032 will fit but is a bit larger and will widen the contacts.. if someone put 2032's in previously, you can put 2032s back in .. just don't mix the 2

[@brookelittle1834]

Thank you for this post! I have a 2007 Mercedes ML-63. My fob will not lock the car and now it is starting to not start the car. I replaced the battery and it is still doing this. What do you recommend?

[@fupabox]

Brooke Little I don't have lot of experience with that key..the ones I have had have never had any issues.. I did find a forum post that may help you..mbworld.org/forums/e-class-w210/413842-ignition-switch-sometimes-doesn-t-recognizes-remote-key.html

[@MrBlavatsky]

great vid, managed to get my glued key apart after cutting two of my fingers (ouch) but still only getting the red led light flash once, put the uv lamp through a camera but still doesn't light, any ideas what it might be : }=

[@markvangemert8302]

Love your video's, was able to do a lot of work on my car that I was othewise afraid to including upper ball joint which I can't believe was relatively so simple for such a cool car. One question, I have an imobilizer chip in my remote and can't for the life of me figure out where this sits in the case, any thougths? Thanks!

[@fupabox]

it should be a little silver flat piece glued to the inside of the case near the red IR lens..it isn't attached to the circuit board

[@markvangemert8302]

***** ah, it is glued to the inside, mine may have "let go" as I found out the scary way that I had an imobilizer as the car wouldn't start once I replaced the FOB. Luckily I found the tiny transponder in the foot well! You make everything look so simple and are fearless.....I live vicariously through you sir! Thanks and warm regards to you and your family this Holiday season.

[@benzox9492]

I always had problem with the case it never worked right for me I always end up putting a screw to hold it together

[@muhammadsaad8479]

What is the exact recommended code of the batteries?

[@mlrlhemsley]

Great post! If the push button is completely off, is there a correct orientation for this? Obviously it's only two choices, but didn't know if it made a difference. Thanks!

[@fupabox]

either way works since the button just completes the circuit side to side

[@mlrlhemsley]

Thanks for that info! Got that soldered back on, re-tinned the other potential trouble spots, tested it, and put it together!!

[@fupabox]

mlrlhemsley working ?

[@mlrlhemsley]

***** Sure is..! I had taken my car for an oil change and when I got it back the remote wasn't working.. of course they wouldn't take responsibility, but thanks to your post all is good! Now I need to figure out the seat controls..

[@fupabox]

mlrlhemsley to re-teach the seats...push the seat control all the way forward then the headrest all the way down...now hold the seat button forward and the headrest button down together for 5 seconds....after that put all the adjustments 1 at a time to each furthest end of travel and once it gets there hold the button for 4-5 seconds..

[@alfamontreal100]

Thanks. That's what I just got. Do you know how the credit card immobiliser remote should work. How do you disarm it when starting the car? Should it recognise the key and just do it automatically? Seems to auto set when you remove the igniton key ok.D

[@fupabox]

I'm not sure how those work. I guess they use the credit card to allow power to go to the ignition key..no credit card, no start..they've been around forever but I've never used one

[@chombito1]

thanx again bro

[@Gimbergp]

Do you know a way to program my my remote key to my car. I have a.1997 Mercedes Benz E320. I have two remote keys(they're the same as the one you're using in the the video) for them and none of them work, the light only blinks then nothing happens.

[@fupabox]

Gimberg Preval point the key remote at the rear (inside) view mirror..press unlock on the remote..then start the car within 5 seconds

[@sethjobu562]

Hello fupabox. I have a 1998 c280 mercedes. My key has completely stopped working. I have in the past changed the batteries successfully with the help of your video, but recently I think dropped my keys and damaged the circuit board (chip?). I have tried new batteries but nothing is generating the infrared? light needed. Is there any way to fix a damaged circuit? I don't see anything loose to sauter but that is to my untrained eye. Another major problem (the major problem) I am having which I think is related - my car won't start. I can unlock my car manually thru trunk or side door but when I stick the key and turn, the engine sounds like it is about to start but doesnt. In the past, even when my key batteries were dead i could still remotely enter and start my car. Any recommendations and do you think it's possible the car won't start because the circuit board is damaged? I want to try and narrow the problems down before I spend hundreds and hundreds of dollars getting car towed and fixed. Great video and thank you. Seth.

[@fupabox]

the chip in the key fob isn't sending a signal to the ring around the ignition keyhole..You may need to take it to an electronics repair shop..maybe they can see the problem on the board

[@sethjobu562]

I will definetely give it a shot and bring it by the local electronics shop. Do you know if it's possible to buy a new chip just in case? Do you believe the reason the car isn't starting is because the chip isn't sending a signal to the ring around the ignition? I am trying to narrow down possibilities and would almost be a relief to think that. Thanks a bunch fupabox.

[@fupabox]

the chip will send a signal to the ring..but the key isn't recognized (no infrared) so the car isn't making the match..it's possible only the led is bad..did you check for infrared flashes with your phone camera ? also you can try the reset .. reset procedure...point the remote at the drivers door handle IR reciever ..press the lock/unlock button on the remote once,then start car within 30 seconds..if remote doesn't open the door, lock it with the key..then unlock with the key and attempt to start within 30 seconds...

[@sethjobu562]

+fupabox I did check for infrared flashes with my phone cam numerous times and haven't got a single flash. I have done the lock/unlock procedure manually with the key but it didn't didn't start. I haven't tried it with the remote because remote isn't working at all. I had triple aaa come out and try and give me a jump, but that didn't work either and they tested the battery and said that was fine too.

[@fupabox]

Seth Jobu unfortunately it sounds like the key circuit board is bad..maybe an electronics repair place can see something on the board..I figured you had tried the reset with the key , but it was worth a shot.

[@kchilz32]

where can I get a remote for cheap? when I bought the car the shell was empty. thanks for your awesome videos!

[@fupabox]

+kchilz32 unfortunately the dealer may be the only answer.

[@lupuization]

Hi, helpful video but I can't see the transponder in that key. is there one?

[@fupabox]

it isn't the same as the little black chip in the newer versions..it is built into the board

[@federicoulloa15]

The problem I have with mine.. batteries are consumed too fast... i have to change it once per month aprox.. do you have any idea which could be the problem? thanks.

[@fupabox]

prob. a sticky button, or the light is staying lit. Not really sure

[@MegaMusical10]

Can you repair these as a part-job, we need help.

[@smeianumihai2872]

This key has transponder ? Can i use a different key without the remote after a sync ? thanks.

[@fupabox]

the key has an electronic chip in it, so it won't work without a chipped key

[@shedrachamen8805]

hi which of websites one can learn how to repair

[@eddydar]

Hi I'm after a spare key for my van its the same as in your video. Can I reuse reprogamme a second one of ebay with a new key blade cut to suit.

[@fupabox]

I'm not too sure on how the programming works, if you can use one that is already mated to another car...I'm sure someone can do it