W169 remotes locking unreliable and getting worse

[Tombob]

Howdy all,

I have a W169 A170 Elegance that my partner inherited from her mother. There aren't many of these in Australia so knowledge is not easy to find - even the Merc specialists just tell me to sell it before the CVT gives up the ghost. I'm hoping someone here can give me some hints on fixing it.

It's clearly been through the wars because when we got it the list was appalling:

- AC compressor electronics fried ... sometimes just stopped working then started again (new compressor)
- Front suspension shot (new shocks, mounts, bump stops and track rod after only 80k Km)
- Audio20 fried (tried replacing fuse at back of unit but just blew again, replaced from scrappers)
- phone system draining battery (found unit under the passenger seat and disconnected it)
- Remotes unreliable (replaced batteries but both still occasional at best. Central locking button on door works fine)
- Door lock barrel broken (so couldn't open door with key ... replaced barrel but for while had to leave it unlocked ... in SYDNEY!)

No sign of past water ingress through the pollen filter but I can't rule out anything.

Next is the remote locking. I'm more familiar with VW electrics but I am prepared stretch my skill set.
I understand there's both RF and IR? When not working even pointing key at the IR receiver in the driver's door handle does nothing. How does this system work and how do I diagnose it? Do I need any specific tools?

Not sure if I'm backing the right horse but I've come this far and I'm hoping the finish line will appear soon ... if it doesn't finish me first.

Cheers,
Tom

 

[mattkh]

No sign of past water ingress through the pollen filter but I can't rule out anything.
Tom

Has it stopped raining..?
If the phone system was draining the battery, then it definitely had water getting thru the pollen filter sometime in the past.
You have managed to fix so many items. Well done.
Check the wiring to the roof aerial for the remote locking.

 

[Tombob]

Matt, thanks for the reply and apologies for not responding earlier.
To bring the topics together it actually has stopped raining in Sydney but we've had the worst floods in 50 years and I've been busy helping a friend clean out his flooded house ... which also flooded the local sewage works. But no sign of water in the Merc so I'll take what wins I can.

Ah, so the antenna for the RF remote is the roof antenna. Is there a smart way to check this or does this require removing the roof lining ... or just access from the trunk?

From what I understand the IR is a back-up to the RF and the receiver is in the driver's door handle. I'm guessing I have issues with both.
The remotes stopped working completely, even when pointed directly at the receiver, after a local garage replaced the door-lock barrel. I'm guessing poor electrical connection caused the intermittency and perhaps the garage inadvertently separated the contacts completely. Does that sound reasonable or is my understanding off?
Cheers,
Tom

 

[mattkh]

Glad it has stopped raining.
Sooooo the remotes stopped working after the barrel was changed..?
What year is the car.? MIne is a 2000 but W168.
Is it a right hand drive..?

 

[Tombob]

2006 W169 RHD (Australia)
Remote opening was occasional at best but after the barrel was changed not at all. Even when it did work I had to point the key directly at the IR receiver in the handle and cross my fingers - I suspect the RF function has never worked (while I've owned the car).
The driver's door inner panel has obviously been off before so perhaps a clumsy mechanic broke a wire or a plug and a vigorous drive temporarily fixes it ... or fiddling with the IR plug breaks it.

 

[mattkh]

Thanks.
What we need to establish is whether the locking mechanism on your car is vacuum operated or electronically operated. Is there any way you can check that.
A useful knowledge base I have used is Albert Rowe's a class info.

 

[Tombob]

Electric locks - I replaced the rear RH lock when the lock/unlock retention spring broke (a common issue I understand). They work fine when I push the central lock/unlock buttons on the driver's door.

I looked at Bert's lock earlier. Perhaps my keys need resynching to the car but my key is different to his. My key only has 2 buttons: a lock and an unlock and there's space for a third button to open the boot but there's no switch under it (I assume this was an option but not installed). Is there a resynch procedure for my key type?

 

[mattkh]

Thanks.
If you press the lock or unlock button and see the front of the key through a digital camera. do you see a dot.
If not, then the key is not sending a signal.
There has to be a wire going through the A pillar used for the locks on the doors.
Can you see anything wrong in the door hinge area where the wires go through from the pillar to the door..?

 

[FiveAlive]

As @mattkh says, if you look at the front of the key through a digital camera (or your phone's camera function) whilst you press the key, it should show the IR signal because digital cameras can 'see' IR and show it as red. Also, the key has a small LED above the buttons, which should light up when the buttons are pressed. This will prove that the key is working.

The IR sensor is connected to the door control module, and that talks by CAN to the other modules inside the car. You say that the doors lock and unlock when you press the buttons in the driver's door. This rules out any wiring issue between the door control module and the other modules in the car and, in any case, if the door control module comms were not working then you'd also have problems with controlling the passenger door mirror and electric window. So the most likely failures are, in no particular order:
- Key buttons worn out or other internal fault within the key
- Key battery flat
- Radio receiver is bust (my understanding is that this is in the top of the dashboard)
- IR receiver, or wiring from IR receiver to door control module, is broken (need to take the door card off to check that)
- Key is not paired to car: this wouldn't cause the intermittent failures that you originally saw, though

 

[Tombob]

Thanks @mattkh and @FiveAlive.

I see a red blink in the camera when I press either of the buttons and on both keys. Batteries were replaced earlier and my local shoe-repair-phone-repair-key-cut-remote-lock-programmer-in-a-kiosk at the shopping centre confirmed the keys were emitting an RF signal.

The IR receiver is integrated into the door lock so it was replaced when the lock was switched with one from the breakers and this didn't fix the IR issue. I think it's highly unlikely both IR receivers were broken so my suspicion is now firmly with a bad connection between the receiver and the door control module. I guess I'll have to drill out the rivets and take off the inner panel.

I'll check the IR first - is there a specific fuse to check first or if the central lock/unlock button works then it can't be the fuse?
As for the RF I guess that's somewhere between the roof aerial (as @mattkh suggested) and the electronic module in the dash beside the central air vents (as @FiveAlive suggested).
Given I've had to replace so much electronics already my money's on the module being fried. If I replace that from the breakers must I resynch my keys to the new module?

 

[mattkh]

2006 W169 RHD (Australia)

Have you tried this to resync the key.
First unlock the driver door using your current technique, because you will need to sit in the car within seconds.

Point the key at the driver door handle from a very close range and press the unlock button - then stick the key in the ignition and turn it to 2nd position within 30 secs.

 

[V6Matty]

The RF receiver is part of the rear windscreen like the radio receiver, how do the tracks look, also what’s the radio signal like in general if poor then could be a chafed wire in the rear hing area which would explain the intermittent nature of it.
Oh and don’t bother trying to chase down the IR, they are useles and fail all the time, even if you bough a new one don’t expect them to last more than a few years

 

[Tombob]

Thanks all for help. I really appreciate it - not even my local Mercedes specialists know these cars.

Righto.
I tried resynching both keys but no luck with either - I pressed the open button, pointing directly and closely to the IR receiver then immediately reached through the open window and inserted and turned the key to the second position.

The rubber boots next to the rear door hinges are in good condition so I'm presuming the wires inside are also good.

The radio was replaced with so many other fried electronic components but the reception with the replacement Audio 20 is fine for AM and FM.

When you say the RF receiver is "part of the rear windscreen" I'm confused. There's a stubby aerial centre of the roof just forward of the rear door. Is this what you mean? Other than that I can only see the demister integrated into the glass. If that's doing double duty then those tracks seem in good condition. Pictures attached (+ pic of key).
Could cars delivered to Aus not have RF (I doubt it but who knows)?

 

[mattkh]

Thanks especially for the photos.
Try putting the key in the ignition, then press firmly any of the lock/unlock buttons to get sync.

Does the front passenger door have a key hole..? Do you have the metal key to insert into it..?
When the barrel on the driver's door was changed, you got a new metal key, right. Did you open the fob to replace the metal part or the garage..?

 

[Tombob]

No go.
I just tried both keys methodically: first after just inserting the key and pushing one button then the other, then again doing the same in key position 1 then again in key position 2.

The barrel from the breakers came with a metal key insert and this is the only way of unlocking the car. We still have the original barrel (in which the keys just spin freely without spinning the disc at the back of the lock) plus the both original metal key inserts. My local locksmith is vaguely confident they can swap barrels from lock cases so we can retain the original keys.

Only the driver's door has a key slot (i.e. no go on passenger door).

 

[mattkh]

Thanks.
Please can you confirm one other thing for me.
Open and close the passenger door.
Put the driver door window all the way down. Get out of the car, close the door.
Now with a finger push down the cap on the driver door to lock the door.
Did this action lock the passenger door..?

 

[Tombob]

Thanks @mattkh.

Only the driver's door locked and without the usual solenoid clunk I get when I press the central lock button on the door arm rest (when all doors lock).

If it's relevant, after I manually unlock the driver's door with the metal key insert, when I pull the door handle all locks open.

 

[mattkh]

Thanks very much. Every detail is relevant.
Intermittent electrical problems on cars can be as a result of a failing earth contact. The closest such connection on your car is on the driver side behind the panel to the right of your right foot. Rowe's website item 37 of the W169 index is your guide.
Do you have a chart of the fuses, it is normally in a pocket next to the battery under the driver's foot..?

 

[Tombob]

Thanks @mattkh and @V6Matty for your help.
The auto gearbox went today so my planned weekend remote work has been towed to a friends garage.

As I was taking off at the lights there was a moderate "bang" and then no drive. In forward or reverse the gearbox gave only a faint grinding and whirring sound but no traction. I pushed the car to the curb and had it towed.
I will postpone the remote fix for a few weeks ... or possibly forever if the gearbox quote is as high as I've heard some speculate. Seems a shame but this car is fighting me all the way.

 

[V6Matty]

Ouch, have a feeling it will be the input shaft bearing that’s collapsed, if that’s the case then I’m afraid your looking £1500 ish with a rebuild, mainly due to labour rate as the engine and gearbox have to come out as one, and they are a pain on the 169.
I feel your pain though as we had something very similar happen to ours a few years ago