revisiting infrared remote system malfunction

[CDNC36AMG]

Originally posted by tecqboy
In the case of our cars, I'm thinking the problem is something like corroded connectors, cracked solder joints, or salt water damage.

I agree. As I said earlier in the thread, some have reported on the SL forum over time that cleaning alarm and/or lock wiring has cured their ills. As has checking the related alarm/door fuses.

My problems are soooo variable and not at all light related.

[LeaUK]

tecboy - I too am an electronic design eng. and also have the exact thoughts as you on IR devices. I'm not sure of the manufacture of ones used in the MB as the IR receiver is unfortunately part of what looks like a single moulding.

I can however say that I've inspected mine thoroughly and will say that there is ZERO sign of corrosion where the IR module connects to the body - 7 or so gold plated custom pins - they look like new.

My hypotheses is that the AGC/noise circuit within the sensor is either failing or is being disturbed by ambient light such that it cannot differentiate between the IR code and noise - but why I still cannot understand.

Modern IR receivers incorporate very narrow band filters and therefore I find it difficult to believe that the IR filter on the door is affecting it - so my next step is to prove it.

This weekend I'll strip the sensor from the barrel and attempt to locate the manufacturer, then carry our some tests - maybe taking the plastic IR filter off and replacing it with a known good unscratched lens.

Why the effort some of you may think - well I've just been told by MB that the IR module is NOT available separate to the lock!!! Now that's gota hurt!!


CDNC36AMG

Are you definitely sure it's not light sensitive? Do yours work at night - I mean when it's pitch black? Does your drivers door fail more regularly? If so these are classic symptoms of IR sensor failure.

Forget wiring or connects - the only pin/connector failure I've ever seen on a MB is where they are literally exposed to the outside elements. I've never seen defective connectors internally. Unplug your alarm module and look at the contacts - they will be like new, perfect!


I'll keep you all posted as I discover things.

Lea

[Gilly]

MB does have some info that I saw that does state that ambient light can affect the range of the IR system. It creates what I belive they referred to as static or interference. They did also state this is more evident in lighter coloered cars, esp silver.

Gilly

[LeaUK]

IR is severely effected by sunlight, tungsten or even fluorescent light (well the ballasts of the driver not the actual light spectrum) and indeed is often referred to 'interference'.

Gilly - my IR range isn't 'affected' by sunlight it's eliminated!

I have two questions for MB.

1. Can I buy the sensor assy. without the barrel and if not, why not, as these are clearly separate assemblies?

2. Why did MB change to a single IR receiver in '98 - seems very suspicious to me! Coming from the design world there two over whelming reasons for design change; design/manufacture error and cost.

I doubt it was for cost reasons (due to limited number of cars sold and total car value) and so I have my suspicions of design error. And it took around 10 years to discover and implement the change - perhaps I'm just a sceptic!?

More testing tomorrow

[CDNC36AMG]

Originally posted by Learoy
CDNC36AMG

Are you definitely sure it's not light sensitive? Do yours work at night - I mean when it's pitch black? Does your drivers door fail more regularly? If so these are classic symptoms of IR sensor failure.

I'm comfortable that it's not light sensitivity causing my problems. I have the same issues in my garage in the dark at night.

My problems are intermittent on all three locks. Remote fails roughly 50% on pass. door, 70% on driver door and 5% on the trunk.

When the driver's door or trunk remote fails the key doesn't work either. When all fail at once then only the pass. door will lock or unlock with the key.

The question then is....are others having key failures as well?

[Gilly]

1. Can I buy the sensor assy. without the barrel and if not, why not, as these are clearly separate assemblies?

MB certainly DOES sell the IR receivers, you don't need to buy the handles to replace the IR receivers. I would agree this is probably the problem. I have replaced several receivers. Check with Phil at Fastlane.

Gilly - my IR range isn't 'affected' by sunlight it's eliminated!

I would say that "elimination" would be an "affect".

2. Why did MB change to a single IR receiver in '98 - seems very suspicious to me! Coming from the design world there two over whelming reasons for design change; design/manufacture error and cost.

They had at least 2 receivers in 98, the left and right door. i can't remember on the trunk, I believe there wasn't one in 98. They redesigned the whole thing I guess you'd say in 1998. The receivers were different in that they no longer contained the red and green lights any longer. Instead of those they flashed the parking lights when locking or unlocking, not the red or green lights. One big advantage to this was that the entire surface area of the receiver was now "all receiver", no more red and green lights taking up "valuable real estate" on the receiver surface, and they do seem to work alot better for the IR function. Of course by then the locking/unlocking functions were via RF not IR, with RF you have alot better range. But MB wanted the convenience functions (summer opening and convenience closing) via IR so it would remain line-of-sight due to safety considerations. So I don't have a good answer as to why one receiver was dropped, but as to the other changes, it was just plain "progress" I'd say, the RF unlocking has alot better range, MB was probably just getting alot of complaints about the small range of the IR unlocking. At least that was the main reason they gave for changing over to RF for remote locking. MB STILL uses IR for operations like window/sunroof operations and on the new SL you can also operate the entire roof outside the car via IR, they still want line-of-sight when operating something that can injure someone, like a side window for example.

If you are thinking the key may be bad, you can go to Radio Shack for example and buy this small credit-card sized tester. What I've heard is you need to leave it out in the light for awhile, then take it into a darkened room and aim and activate any IR device (TV Remote, etc) at this test card and the IR will show up on the card as visible light. Mainly sold for testing remote controls for various devices, but you can test an IR key with it.

Gilly

[LeaUK]

Gilly

Are you saying that in '98 SLs had both RF and IR? If so, then surely this was in one key - maybe these new keys have two buttons? As you say, one for convenience and one for CL/alarm.

According to AllDataDIY, as of 09/95 MB the SL changed from IR in the door handles to IR sensors placed just under the rear view mirror - can anyone qualify this with their car?

I still suspect a design issue/ageing and not just complaints about range problems - unless 'range problems' means no range, as in my case! This design change would have cost in the region of 100,000UKP or more; maybe it was made with several other changes?

MB certainly DOES sell the IR receivers, you don't need to buy the handles to replace the IR receivers. I would agree this is probably the problem. I have replaced several receivers. Check with Phil at Fastlane.

The receivers are definitely separate from the door handles as I've already disassembled for closer inspection, but the module is attached to the locking barrel (although there are two pins that allow separation). But MB say they do not sell them separate from the locking barrel. That means at minimum I need to buy the IR module + locking barrel for each door/boot + maybe Ignition barrel (if MB doesn't supply VIN matched barrels) - and that's expensive!

However, I will check with Phil as you mentioned. Thanks for your comments.

Lea

[Momo]

Well, mine is back to acting up. Yesterday morning I arrived at the airport and the remote did not work in the underground parking lot, which was of course pretty dark. The mechanical key always works on all doors. I think the next step will be to replace the passenger side sensor, which definitely does not work, and may be causing the other issues.

Momo

[LeaUK]

Momo

I doubt that one failed sensor would effect the others. All mine operate fine apart from the drivers side which is definitely related to light - but the level of light that causes the problem varies from one day to the next. Sometimes if I just cup my hands around the sensor that's enough, but on others I have to block every single ray of natural sunlight out and place the transmitter directly on the sensor surface. On the occasion the sensor works, if a shine minimal light from a torch on to the sensor, it fails!

I've just finished stripping down the IR module completely to see what's inside and unfortunately it is as expected - a completely molded assembly although it does come away from the lock barrel with ease. I shall post some piccies in a while.

[CDNC36AMG]

Like Momo, my remote issues are on more than one door, but I also have key issues as well.

[LeaUK]

After this morning's testing I can say conclusively that it's the sensor.

The plots below show the IR sensor O/P and were taken at IR module N54 and clearly show the working sensors, no signal is present from the driver's sensor - unless it's dark. Then the signal is as the others.

Final proof.

Hope this helps some others.

BTW - I've removed the middle section in each on purpose ;-)


Boot Sensor:




Passenger Door:




The module and lock itself:





The IR module:

[LeaUK]

Just to let you know that the sensor module and barrel are indeed only available as one - clarification from Phil at Fast Lane has just arrived!

In the UK this part retails for 170UKP inc VAT and so it's now time to find a scrap yard SL or try and melt the potting compound and fault find the electronics within - if only it wasn't potted, this would be easy!

I'll keep you informed - should you not be bored of my tale as yet? !

[tecqboy]

Very Interesting. Thanks... Geez; why is nothing about these cars ever easy? I understand that the barrel and the receiver need to be matched so as the physical key and the IR code match. But where is the code "de-coded"? In the alarm system or ? Is it reprogramable? I sure do wish I had an electronics diagram of my car?

[LeaUK]

tecboy

Schematic diagrams are available at AllDataDIY and I can 100% recommend this service as it has tonnes of info - more than you will ever be able to find Googling.

AllData have full schematics and is the sole reason I could locate which pins to probe and achieve the diagnosis re the IR sensors above. Of course the individual module's schematics aren't available but that's governed by the manufacturer.

I can see no logical reason for the barrel and IR receiver to be matched or indeed by reviewing the signals and schematics, so I strongly suspect there is no reason. The IR module's role is just to filter and transmit the code emanating from your IR transmitter back to the N54 IR module (in your boot), it is here that the decoding is carried out. If you change this you will definitely need to change your IR remote or make sure the N54 is supplied my MB who will ensure it's pre-programmed for your VIN.

Update

AllData say:

"The receiver units can be exchanged individually without specifying the code number."




Lea

[Gilly]

Yes, the receiver in the door can be simply regarded as an "antenna", they are all the same, not vehicle-specific.

Gilly