Non-Functioning IR Central Locking Feature
 

The IR function for central locking in my ’96 SL600 has stopped working. My central locking feature works perfectly if the mechanical key is used in any of the locks. Thus, only the IR function is inoperable.

However, whenever I use the mechanical key to lock/unlock the car, the red/green lights on the rear view mirror are *not* blinking. I cannot remember if they blink whenever a mechanical key is used, or whether they are for IR operations only.

Question #1 – Can someone test with a similar vintage SL- or S-class, using a mechanical key, to see if the red/green indicators on the rear view mirror blink when using a mechanical key?

Question #2 – Assuming the non-blinking red/green lights (when using a mechanical key) imply the IR function is not working, what components make up the circuit? (Circuit board within the mirror is one, but what does it feed, etc.?)

Any and all input is welcomed! Thanks in advance.

Cheers,
Jeff

I've posted the same exact question here and stumped the techs, as they fumbled about in the dark.

Same thing, my remote can arm/disarm the alarm, and I see the green/red leds flash on the mirror, but the doors do not open/close anymore. For a while they were sporadic, but now they dont work. It works perfectly if I use the key in the lock, or if I use the lock button inside the car.

My indie is ordering a locking computer next week, and after installing it I will bring it to the dealer to reprogram to my key. He's pretty sure its my locking computer that is faulty, so I'll post up if it works.

Mine's a 96 also.

The 1996 is the only year that has the mirror mounted LED's.

Thanks spinedoc for the information. However, our symptoms are different. Your IR Remote causes the red/green lights to flash, indicating the vehicle has received the IR signal - it may not be processing the signal, but your car is receiving it. In my case, the red/green lights do not flash, implying my car is not receiving a signal.

My problem *could* be a bad remote transmitter. But I would like to troubleshoot the problem a bit before making the investment in another key remote.

Oh joy…

Thanks guys for the thoughts.
Cheers,
Jeff

Jeff have you replaced the battery in your remote?

BTW to answer your question, no the leds do not blink when using a key in the doorlock.

Thanks spinedoc! Yes, I have changed the batteries... with the same result.

If your red/green lights do not blink when using the mechanical key, then I am back to not knowing whether my remote has simply failed or if there is an electrical fault in the IR Sensing circuitry. However, in testing my '94 SL500, the red/green lights (mounted in the door handle) do blink when using the mechanical key. Now it is possible the two systems do not use the *exact* same logic, but the red/green lights sequence should probably be the same throughout the R129 model.

My Owner's Manual is quite vague on the whole subject. Nevertheless, I’m going to try resynchronizing the remote to the car.

Anyone else have any ideas, suggestions or comments?

Cheers,
Jeff

Take my answer with a grain of salt, as my remote locking system is fubared at the moment. I cannot remember if the leds flashed when using the key in the door locks when the system used to work. I rarely ever used the key in the lock.

Keep me posted as I'm hoping your problem might be related to mine.

I'm really hoping someone can help by describing where the IR signal goes after leaving the rear view mirror (or door handle for pre-96 models). I have a '94 SL500 that I can swap parts around (assuming their interchangable). But at the moment, have no idea where the circuit leads.
Cheers,
Jeff

I believe the signal goes to the central locking module which is located in the trunk above the battery. From there it sends a signal to the vacuum pump to open/close the doors. I'm no mechanic and only gleaned this educated guess from reading many many posts on the remote locking system.

What really confuses me is that doing a search there must be dozens of SL owners with problems with their remote locking system, but none of the tech/smart guys on here have any suggestions. Even my indie is baffled, my next step is the dealer.

BTW have you tried to resync the remote? Point remote at mirror, press briefly twice, then within 30 seconds put the key in ignition and turn to position 2. Seems to have worked for some. Also make sure as I mentioned, you have a fresh battery in the remote.

Do you own a digital camera with an LCD view screen for framing up the picture? The image sensors in digital cameras are usually sensitive to the IR wavelenght transmitted by the remotes. Set the camera up to take a picture, then aim the remote at the camera and activate it. If you see a bright spot from the remote, it's probably OK. This test doesn't always work...It depends on the camera. And if it does light, it doesn't mean it's transmitting the proper code. But chances are that if both remotes light, at least one has proper code. In my experience, the IR sensor diode in the receiver module is a likely suspect for failure. That's what usually fails in TV set remote receivers. It wouldn't be too difficult for an electronic tech to diagnose / check the receiver for a bad sensor diode, but I realize you don't have that option, especially since the receiver is part of the mirror assembly.

Jeff, if I'm not mistaking your car car is OBD II and you can get a diagnostic reading at your local stealership (free at mine in SoCal).

My indie says I have no OBDII error codes related to the remote locking system.

tecqboy any idea if it's possible for the remote to trigger the red/green leds, but NOT trigger the door locks/alarm? That's what mine is doing.

Good discussion going here – thanks spinedoc, tecqboy and lynns for the input.

I tried resyncing the remote with the vehicle the other day; no effect, no change in symptoms.

Regarding OBDII codes... purely coincidental to this problem, I had to pull the codes yesterday while troubleshooting a severe cylinder-7-8-9 misfire problem. (Still a mystery to me as the problem went away by itself. But that may be a new thread!) The misfire problem caused applicable codes for the affected cylinders, but there were no other codes, Center Locking or otherwise.

Today, I tried the suggestion by tecqboy using a pair of Olympus cameras. Neither captured any indication from the remote. However, I did notice that the little LED inside, behind the red lens, of the remote did *not* blink. This is a very recent development as the LED was blinking earlier in the week. If memory serves, the LED blinks to indicate remote operation and occurs if you hold down the remote button for 2-3 seconds. It’s a fair indicator of battery life, etc. (The batteries n the remote were changed a couple days ago, as a test, so I know they are OK.) I know it is not supposed to be a continuous blink.

With today’s development of non-blinking remote LED, I would normally think the remote is bad. However, the red/green indicators on the mirror do not blink when the mechanical key is used. I want to say this indicates the vehicle is at fault, but cannot say with absolute certainly. Hence, I am hoping someone with a ’96 can confirm that the red/green lights blink when using the mechanical key. This, I think, is the best, definitive test to determine whether the remote or the vehicle is at fault.

Finally, to really complicate matters, some of you may recall that I recently performed surgery on my rear view mirror to solve the infamous R129 Mirror Shake problem (http://www.peachparts.com/shopforum/mercedes-benz-sl-discussion-forum/198658-repairing-r129-rear-view-mirror-shakes-jiggles.html), but that work was completed over two weeks ago and I know absolutely the IR Central Locking System worked after the mirror repair as I used it multiple times after the mirror repair.

Regardless, I will disassemble the mirror today, just to satisfy myself that the connector/cable inside is properly seated and will make sure the red/green lights are properly connected. I’ll also poke around at the controller above the battery (spinedoc’s input as to controller location), though I have not been in that area for many months. Who knows?

Thanks again, and please keep the ideas coming. The more we pool our ideas today, the more knowledge that will be documented to help folks tomorrow.

Cheers,
Jeff

I have a question that I hope isn't too far afield from this: On my newly acquired '96 SL500, what beyond the doors and trunk does, or should, the central locking system lock? I tried locking the car with the remote while sitting in it, the door locks went down, but none of the interior compartments were locked.

Thanks,
Alan

On mine the center dash and console lock with the central locking system.

BTW guys mine is fixed, it turned out to be a corroded connector under the drivers dash. Amazing how the simple things can sometimes be the hardest to troubleshoot.

no lights
 

i have a 96 320sl, i just locked and unlocked using the key manually and the lights did not illuminate. i hope this helps you

Do you have a lock in the middle of your dash? If yes, that should lock everything else; door holders, center console, etc. But yes when the tops down and you are at the beach you will need to lock both before you get out.

The Kivos, 1994 SL500 35K

I do have the lock, but turning it locks/unlocks only the dashboard "glove box"; nothing else happens.

Does anyone know what controls the locking of the secondary items, like the globe box and armrest, when using either the dashboard central locking key switch or the infrared remote?

Please read your 1996 SL Operator's Manual, pages 27-32 for this information. If you don't have one you can download one at R129 'Owners Manual' download site

Thanks ANC4. Your information suggests my IR Key is defective. Unfortunately, there does not appear to be any method for testing the IR output of the IR Key. Guess I'll bite the bullet, order one and see what happens. Thanks everyone for your thoughts and ideas.
Cheers,
Jeff

I did read the manual, actually; that's where I started. l posted the question because (a) it doesn't happen in my car and (b) eyeballing of the supposedly locking compartments reveals no obvious locking mechanism on most of them (door pockets, rear compartments, center armrest).

I took this as a community of people available to share information and knowledge; was I wrong?

Alan

No, you are not wrong - this is a community of Mercedes enthusiasts who share information. However, you may receive answers that are short and easily misinterpreted as indifferent. We all have stuff to learn... and stuff to share.

Moving forward, I just tested the locking function of my '96 SL600. Because of my IR recognition problem, I could only test this with the driver's window down, using the key in the driver's door lock. While I was sitting in the driver's seat, arm out the window, when I turned the key, the following items locked down:
- Both Doors
- Center Console Armrest
- Center Console Roll Top
- Eyeglass Compartment in Dash

Hope this answers your question about what items lock down. The actuators all use vacuum, and if some of these do not work properly in your car, I'd start with a vacuum hose connection around the vacuum pump. It's located in the trunk, over the battery. Good luck.

Cheers,
Jeff

Radio Shack sells a little card for testing IR emitters. You first "charge" the card by exposing it to a flourescent lamp, then hold it in front of the emitter, and it will glow if the IR emitter is producing light. The cost is minimal, under $5. I use it to check the IR emitters on various machines I have worked on.
As someone mentions in a future post, many digital cameras will also show infrared light - you can test yours easily by pointing a remote at the camera, pressing a button, and looking at the display to see if the IR beam shows.

WOW - Way cool! Thanks Richard for the lead. I'll check it out.
Cheers,
Jeff

Many digital cameras are responsive to IR light. You can aim your remote at one while looking at the view screen. Press the remote and if it's working, it'll shine like a flashlite on the screen. The "hitch" here is that not all digital camera's will respond to IR, so it's not a sure bet.

Jeff, the 'storage compartment behind the passenger seat' should also lock. Note: I have found that many of us don't use this compartment and therefore don't even know that it exists.

Lynns, Yup - I did forget about them! You are correct; the two compartments should lock down. Yeah, since the one behind the driver’s seat is filled with Bose sound stuff, I do not even think of ‘em... except when the lids rattle because they do not latch properly. But that's for another thread! Thanks for jogging the memory.
Cheers,
Jeff

Many thanks, Jeff! I'll track down and check the vacuum connections. I appreciate the help.

Alan

Hmm my center console roll top does not lock down, I'll have to take a closer look.

I always thought it was humorous that the Center Console Roll Top of my '96 SL600 locked down. In my car, the center console only has room for the two factory-installed cup holders. Are they *that* expensive that require them to be locked down when I'm not in the car?!?
Cheers (with LOL),
Jeff

Lol, I agree, but my wife does keep her nice Pradas in there. I can hear the latch clicking, but it does not pop up, hmm.

Solved it. I got a diagram of the vacuum locking system, traced the lines and found a break in the right rear storage compartment. I put a toothpick in that line to seal it, and voila!, I have locking in the console compartment, sliding cupholder compartment and eyeglasses storage in the dash. The door compartments no longer lock in the '96 model year.

Jeff, while researching something closely related I came up with this PDF from my R129 Service DVD. It looks like the PSE vacume pump is known for failure and something for you to consider. Please read the attached PDF. p/n 1298000848 is $388.70 at www************

This deserves some closure. I got a diagram of the central locking system, started tracing the vacuum lines, and found a broken connection in the right (passenger-side) rear storage compartment. I put a toothpick into that line and voila!: I have locking internal compartments.

Thanks again for the help. I'm reminded once again that none of us is as smart as all of us.

Alan

Thanks Lynn for the great information - I'll check it out!
Cheers,
Jeff

Although it has been a while, the problem turned out to be a bad key remote. With nothing else to try or check, I 'bit the bullet' and purchased a replacement key remote from the local delaer. Problem fixed. Guess they do wear out over time, though I'm not sure how.
Cheers,
Jeff

Testing the IR Remote Lock/Unlock
 

This has been dormant for a while, but it is still the best thread on this issue, so I thought I would post what I learned trouble-shooting my '96 SL 500.

1. You can test the remote easily with an i-Phone. Just view it like you are taking a picture and press the remote's button, and you will see a flash if the remote is working.

2. The remote lock/unlock flow is from the receiver under the mirror to the remote control lock (RCL) module (n54/1) behind the passenger air bag.

3. The RCL sends a signal to the PSE (vacuum) pump controller to tell the pump to unlock the doors and trunk.

4. It also (I believe) via the CAN, tells the rest of the electronics that the vehicle is unlocked and it is OK to provide fuel and spark when the key is turned to start.

If the remote is transmitting, the next step is to see if the receiver is signalling the RCL module. This can be tested by probing the green/violet wire (pin 7 on the RCL) and connecting a meter between it and ground. You should see app. 12 v. which will drop by about a volt when the remote is pressed.

The location of the RCL moved around in the 90's. Up to '95, it is supposedly in the trunk by the fuel fill. In '96, it moved behind the passenger air bag and is accessed by removing the plasic under-panel. That's where I found it on my car. In later years it supposedly moved to the left of the sterring wheel.

On my car, there is a twelve-pin connector and separate two-pin connector for the CAN.