R129 - remote control & trunk lock occasionally fail to unlock car!

[detailas]

Hi guys, I've been encountering foll problem lately. My R129 SL320 '96 is not a daily driver and she gets cranked up every 10-12 days or something. She also has a new battery.

Couple of weeks ago I tried to unlock car (by remote control as always) but to no avail and then tried to unlock the car from the trunk lock by using / turning the key counterclockwise, again with no result - all doors / trunk stayed locked. I re-tried for a few minutes but without a result. I figured that due to the fact that she hasn't been cranked up for like 10-12 days, the battery might have been dead (although the battery is only 2 months old) - however I noticed that the alarm blinking indication light in the cabin was indeed blinking (which I guess it means that there is still some power in the battery, enough to power the central locking vacuum lines enabling me to physically unlock the trunk with the key).

Next morning I decided to give her another try before calling an MB technician - and by only using the remote control - voila, all doors / trunk immediately unlocked, I entered car, cranked up and drove away.

The exact same thing happened last night - and this morning I made another try and everything working normally again.

Any ideas? I have been through some other posts / threads describing similar symptoms but could not find anyone with identical experience.


George


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[jjrodger]

There was a lengthy post on this forum about deteriorating IR sensors. You may will find it if you search under "IR", I would have thought. One of the posters was LeaUK.

In future, you can normally secure access using the key in the driver's door lock.

Good luck!

[detailas]

Originally Posted by jjrodger

There was a lengthy post on this forum about deteriorating IR sensors. You may will find it if you search under "IR", I would have thought. One of the posters was LeaUK.

In future, you can normally secure access using the key in the driver's door lock.

Good luck!

thanks jjorder, i'll look it up... meantime, please note that due to my updating my black handles to silver ones (post 1998), i do no longer have actual locks in the handles but pseudo-IR instead, therefore only physical lock is the trunk lock.


george

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[LeaUK]

Hi George

So you have no mechanical locks in the door handles - but do you have the IR sensors there?

I note you tried using your key in the mechanical lock in the boot (trunk) but it also failed so I suspect my IR post revisiting infrared remote system malfunction isn't relevant, however it's still worth checking to see if night performance is increased.

I'm not familiar with the lock sensing mechanism to guide much further, sorry.

Maybe others will have some further input.


Cheers
Lea

[detailas]

Lea, thanks for your reply - I have the outside remote sensors, however they are not connected to the system - the remote works thru the rearview mirror receiver.

But you just gave me a nice idea... I will ask my dealer to activate / connect the driver's sensor (i guess by using some extension from the rearview mirror..) and if it works fine, then it means that the rearview mirror receiver is faulty...

Will take the car tomorrow - I will revert with news!

George

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[detailas]

Took the car to the dealer on Monday (along with both remote control keys with new batteries, out of which only 1 was working). First thing he did was to re-program both keys..

I left the car there for 3 days, however he could not reproduce the symptoms - all (un)locking worked o.k. Apart from plugging car to diagnostic computer (which showed nothing), he also cleaned one of the plugs of the central locking pump (located in the trunk on top of the battery)which found rusty green.

Seems that it was the key re-programming - because after that, he demonstrated how the windows go all the way down/up if you keep the remote control button pressed - which I have tried in the past but to no avail.

Anyway, thanking you all for your advice, let's hope problem now solved!

George

P.S. I went to pick up the car an hour ago, but noticed that the antenna did not go all the way down (8-month old hirschmann antenna) - so left the car there to pick it up tomorrow..

Don't you hate it when you take the car to the shop and when you pick it up something else is wrong??


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[LeaUK]

Antenna - that's another common one and you'll be please to know an easy DIY fix. If you go to your dealer you can purchase just the aluminium telescopic section for around 20GBP. It's then simply a case of following the instructions on the back of the packet

Lea

[detailas]

Unfortunately, not a cheap fix... Something's wrong with the motor and the fuse box connected to the motor of the antenna - thus sometimes it goes all the way down, some other times it stops leaving antenna exposed by 20 cms. Will change the whole thing - total cost 120 euros. At least it comes with 2 years guarantee. Oh, well..

George

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[jjrodger]

They all go this way eventually. Mine has, and so has that on a '92 which parks near me.

I would check that replacement of the telescoping antenna doesn't do the trick. My research suggested it would. Even so, 120euros is very cheap for a replacement Hirschmann, in the US they list at $600!

Lea, do you have the part number?

[LeaUK]

Uhm, buried in my files upstairs, I'll dig it out if required no prob. But as JJ suspects I'd be surprised if you need the whole assembly and 120USD sounds like a horrible cheap replacement to me.

I'm an electronic eng. and "Something's wrong with the motor and the fuse box connected to the motor of the antenna" sounds like baloney to me.....


Also, I HATE those cheapy replacements that grind and growl on up and down extension. The Hirschman is silent and the only reason is because - it's expensive.

Spend the 20 quid on the telescopic section first - it will save you in the long run!

Lea