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View Full Version : Trailer Wiring........Scratching My Head!!!! WTF.....MB


WPJ
02-02-2013, 06:23 PM
OK.....NAFTA......2013.....2500....Passenger....wi th factory wiring.

So I plugged in my 7 to 4 way adapter, running lights seem ok, but the right turn is flickering...left turn on, and working ok, right turn on and going from solid on to flicking when,the signal is on

So i tested all of the leads via a meter and all leads seem to have between 11.3 and 12.8v on them when the sprinter is off. Besides the ground line of course... Wtf.. This is factory wiring...

Is this normal....im not an electrical engineer by this doesn't make any sense.

bcislander
02-02-2013, 06:52 PM
OK.....NAFTA......2013.....2500....Passenger....wi th factory wiring.

So I plugged in my 7 to 4 way adapter, running lights seem ok, but the right turn is flickering...left turn on, and working ok, right turn on and going from solid on to flicking when,the signal is on

So i tested all of the leads via a meter and all leads seem to have between 11.3 and 12.8v on them when the sprinter is off. Besides the ground line of course... Wtf.. This is factory wiring...

Is this normal....im not an electrical engineer by this doesn't make any sense.

Is the problem with the trailer lights, the Sprinter lights, or both?

FWIW, I towed my small pop-up camper to Ottawa to give to my son. I used a 7 to 4 way adapter which worked flawlessly.

Maybe your 7 to 4 way adapter is faulty? :thinking:

WPJ
02-02-2013, 07:06 PM
Thanks, ya it could be, but when I pulled the 7way off I tested the leads and they were all hot...strange., waiting for a neighbor he us going to give me another adapter to try.

Oldfartt
02-03-2013, 07:35 AM
This is a quote of mine from a previous thread on this subject.
"If the 25A fuse is fuse 14 under the drivers seat then the wiring (red/yellow) from the fuse goes straight to the trailer connector in front of the rear bumper bar. Option E 57. It supplies an un-switched feed from the battery. It can be used to power the trailer interface unit. A trailer which has LEDs may require to have an extra low value resistor across each circuit for the management system to recognise that the circuit is present. I am in the process of installing an Non OEM trailer interface unit today on my 2011.

An OEM trailer recognition device sends pulses to the trailer connector to identify if there are any lights attached. The pulses measure the current flow and report the status, either normal range, short, or open. If all circuits are open, then "No Trailer connected"
Hence if the trailer has LEDS, the system sees them as a low current and indicates as a fault. There is on the market, a unit which can be attached to the trailer wiring which will allow proper recognition.
It appears in Europe that a failed trailer lamp is deemed to be an offence."

Cheers

Ross

WPJ
02-03-2013, 11:50 AM
Ross, thanks for the reply, my tester is a led light, so maybe I need to, test on a actual trailer. The weird thing is that it is only the right light acting up.

WPJ
02-03-2013, 11:53 AM
In 14, I have a 20a fuse, and I did order e57

sailquik
02-03-2013, 01:03 PM
WPJ,
If the trailer lights do not work WITH A TRAILER....then you have a legitimate reason to go back to your dealer for some warranty sorting of the problem.
Did you check the voltage at the pins on the factory installed 7 way round connector, or on the output of your 7 to 4way adapter.
Perhaps the issue is in your 4 way adapter, NOT with the factory trailer wiring.
Also, since your 2013 will have the TSA (Trailer Stability Assist) testing it at the rear connector WITHOUT a trailer connected may be some or all of the problem.
Roger

WPJ
02-03-2013, 02:50 PM
I'll going to hook it up to a trailer today and test it out

WPJ
02-03-2013, 06:32 PM
OK so I tested with a temporary set of trailer light the magnetic ones and everything seems to work I think this was just my tester pooched.. I
l looking for another one now. I'll let you all know

Oldfartt
02-03-2013, 07:01 PM
You are right. slot 14 is a 20 A fuse.

Cheers

Ross

WPJ
02-03-2013, 07:03 PM
Well it looks like that might just be that way from the monitoring and ecu/tsa. An appointment ther yester did the same thing.

I'm going to try and finish my circuit up and see what I get.

I can report however when the magnetic trailer lights were in and working as expected that when in reverse the tsa turned off the reverse parktronic.

WPJ
02-03-2013, 07:13 PM
Ross,let me know how your install goes today

Oldfartt
02-03-2013, 09:52 PM
The trailer light wiring works fine with a trailer connected on my van as it is a non oem system and the management system only "sees" the van lights and not the trailer wiring. I will not have the trailer stability assist as that function is not activated. In your case you will have the full functionality of TSA I expect.

Cheers

Ross

WPJ
02-03-2013, 10:44 PM
Roger that's what its looking like, I just don't get the added voltage/pulses only on tue right turn/stop signal. Strange..

What wiring module did,you use?

WPJ
02-05-2013, 04:22 PM
Well the tsa I think is the culprit of my issues.

With a trailer on, all lights work fine, no issues.

However I can't get anything else to work and off the wiring. I even tried to just get the turn signals to fire a set of relays and it won't.

Using a dvom, there s a constant 12v on all of the leads even when the signals are on. I am assuming that there needs to be enough of a resistance/load to the computer to send the signals to the circuits for the trailer.

Anyone else have some thoughts

chads
02-05-2013, 04:53 PM
This may be way off but could there be a trace voltage across the wires to detect if there is resistance in the line to sense if a trailer is hooked up, therefore alter the settings on the TSA
in the event the trailer is attached or at least lights attached.
This would not be enough amps to make the bulb work just enough to detect continuity.

Not sure how the van knows your towing a trailer unless there is a manual switch.
Thinking that it is sensed automatically when pluged in.
Kinda like the way some cars sense that a clearance bulb is burned out.
I am not sure how that works just guessing
Chad

WPJ
02-05-2013, 05:17 PM
Chad, yes I think you explained it very well.

If it detects a lamps resistance it turns on the tsa and all is good.

mofo989
02-05-2013, 06:05 PM
Chad, yes I think you explained it very well.

If it detects a lamps resistance it turns on the tsa and all is good.

I wonder which of the 7-pins need to have a load for TSA to be enabled. Any one of them or just a specific one?

WPJ
02-05-2013, 06:10 PM
mofo989 Id let ya know if it was not -13C outside......I have been taking this project in 10 minute exposures......smiles....I think I
m just going to order some pins/terminals and the plastic snap for the back of the tail light section and just make my own T adapter, this way if it messes up any of the turnsignals etc I can just remove it and I have not disturbed the factory wiring.

WPJ
02-05-2013, 06:42 PM
OK So I just ordered the Contacts and Snap on housings to make a set of T Connectors. I will use thise with a set od relays or a powered tail light converter to see how interfacing that way goes.

I'll keep you all posted.

Aqua Puttana
02-05-2013, 07:41 PM
I didn't read, just skimmed this thread.

In case it wasn't revealed here... those little LED quick testers for trailer sockets are notoriously inaccurate for testing many of the modern trailer connector outputs. They just don't provide enough load or proper connected circuity.

Open circuit testing of any trailer socket which is fed by some type of module will often result in seeing phantom 12 volts where not expected. Very few trailer outlet connectors are directly wired into the vehicle wiring. (That is a very good thing.) When the trailer lights (circuit load) are connected then the module uses that feedback to know that the trailer is connected.

Testing with a voltmeter when the trailer lights are not connected will often result in unreliable data. Trailers with low load LED lighting units may not work reliably with some trailer light module designs. FWIW. vic

Oldfartt
02-05-2013, 08:04 PM
Guys, Please re-read post #4 in this thread for the explanation of the trailer monitoring system.
Measuring with a volt meter or low load LED tester is useless where there is no load. The lights need to be in circuit for meaningful readings.

Cheers

Ross

WPJ
02-05-2013, 08:25 PM
Vic yes works fine for a trailer but not for my intended use, my issue though not the sprinters.

Oldfartt/Ross what value resistor did you use to get your less working?

mofo989
02-05-2013, 10:02 PM
Since I just installed the factory wiring harness I wanted to give it a test. I dont have a trailer with 7-way connector. I took it down to the local UHaul place to see if they could test it and they had a device that looked like a multi-meter, but with light bulb. Their diagnosis indicated I ONLY had a RH light not LH.

I was skeptical of their tester device given the computer's detection circuitry which everyone (aside from this forum) seems to deny that it has anything to do with proper operation. They didn't have a 7-pin trailer to test.

I then went to the local tool rental place where they have dozens of trailers w/7-pins and they let me test trailers. Running lights-- Check. Emergency Flashers-- Check. Left turn-- Check. Right Turn-- check. BRAKES--- NOPE!

Why would the brake lights not work? I even tried turning off the vehicle, back on, to allow the computer to "recognize" the circuit, but nope. Tried emergency brake, tried putting in gear... nada. Tried a 2nd trailer on their lot, but nope, no brake lights. Hmm.

Why? My guesses are as follows:

1. I have no brake controller connected, and nothing on the green connector. Do I need to put SOMETHING there to "terminate" it?

2. I screwed up the wiring. I used fuse location #29 (vacant) instead of #30, which is labeled "booster" in the manual. The upper connection in that fuse holder was already occupied with some power connection, so I didn't know what to do with the factory harness' wire. Since I had to install two wires in the fuse box I figured the one there was redundant power. Maybe this was a bad assumption, but I still don't know how it is supposed to be wired there given the existing connection.

3. Didnt have the trailer physically connected with a hitch, is this important for some kind of body electrical ground? If so, why would the other lights work then?

4. Both trailers at place are wired wrong or have the same fault (eg. poorly grounded lights)... grasping, I know...

WPJ, can you see what the back of Fuse holder #30 looks like for you? How many wire going in and out, 2 or 3? In fact, even if you could only take a photo of the fuse holder with the fuse pulled out then I could see by the contacts in the box how many connections are in there.

EDIT: I put a volt meter on the green brake controller connector and measured 11.4v on the black/red to gnd (brown) wire; then pressed the brake pedal and got 12.4v. Not sure what that means... no load on circuit so it could be an open-collector situation or something. But I think this is good news because it means something is happening related to the brake lights and trailer harness!

EDIT2: Hey, looking at the trailer harness wiring for a 7-pin round, they use the SAME wire for directional and braking. This confuses me more as how could the directionals work find but not the brakes? Do trailers use the same bulb and brightness for directionals as well as brakes?

WPJ
02-05-2013, 10:55 PM
Mofo989, I'll have a look tomorrow and let you know what I see, I can't tell with the pic I have now.

sailquik
02-06-2013, 12:31 AM
mofo989,
Did your trailer wiring kit include the PSM (Parametric Special Module) as well as the Trailer Brake Module?
If you have both of these modules installed in your Sprinter, I suspect a visit to an authorized Mercedes Benz
Sprinter dealer/shop to have your ECM/ASR software updated will be the best next move.
AFAIK you are the first person (here on this forum anyway) that has installed the factory wiring ex-factory.
A member from down in Florida had a dealer in So. Florida do the install and it did not work (with similar symptoms
to what you are experiencing) and he could not get it fixed at the dealer in FL.
He stopped by Sun Motor Cars in Mechanicsburg, PA and after the great techs there had exhausted all their
ideas, MB Compliance Engineering was called in and they got a software upgrade from Germany (if I remember
correctly) that fixed the install and made everything in the trailer electronics work as if it had been installed at the
factory.
So, if you cannot get it working correctly, you may want to visit a dealer and have them call the guys at Sun Motor
Cars to see if the feat can be duplicated!
I think the issue is that the TSA (Trailer Stabiity Assist) has to be activiated/programmed so the computers in your
Sprinter can decypher the signals correctly.
Roger

mofo989
02-06-2013, 12:34 AM
No PSM in this install; not required according to the instructions. Hopefully it wont come to that, but thanks for the tip as I will try as a last resort.

EDIT: The thread you reference with the similar issue is here (http://sprinter-source.com/forum/showthread.php?t=22966&page=4). And you are right, it sounds like the same issue. Although I do not have the fast blinking blinker issue, that might have been an unrelated issue as there seemed to have been some complicating trailer differences. I suspect it is sensitive to the lighting load being within a certain spec. That said, it looks like the solution likely is to get the feature coded at the dealer, odd as it is.

Oldfartt
02-06-2013, 08:31 AM
WPJ,
In my installation there are no leds on the trailer.
The minimum load resistor would be the equivalent of a 5W lamp or a 30 ohm resistor. The maximum load wold be the equivalent of a 21w lamp or a resistor of about 7 ohms.
If you are fitting a relay across an existing lighting circuit then the relay resistance should be a minimum of 80 ohms.

Cheers

Ross

aljimenez
05-22-2013, 09:32 PM
I wonder which of the 7-pins need to have a load for TSA to be enabled. Any one of them or just a specific one?
I am looking for the answer to this question, if anyone knows what is it that the TSA uses to recognize a trailer. I want current to flow out of the backup connector, and I suspect having a lamp on that connector is not sufficient for the TSA to "recognize" a trailer is there... Al

mofo989
05-23-2013, 05:23 AM
I am looking for the answer to this question, if anyone knows what is it that the TSA uses to recognize a trailer. I want current to flow out of the backup connector, and I suspect having a lamp on that connector is not sufficient for the TSA to "recognize" a trailer is there... Al

How would you know TSA is enabled? There is not a dash light or indication anyway.

aljimenez
05-23-2013, 01:30 PM
How would you know TSA is enabled? There is not a dash light or indication anyway.
Since I have the fuse, I am assuming TSA is installed and working to identify if a trailer is recognized every time the engine turns on, but I admit I don't know. And I don't know what TSA module does to say there is a trailer and then sends current to its connectors... Al

WPJ
05-23-2013, 02:32 PM
I'm, not so sure of that on just a lamp.

Here is why, I had one of those led trailer light testers...right like no mode, it tested running, left/right/break.

That tester was enough to tell the sprinter there is a trailer attached here and it disabled Tue rear parktronic system....

aljimenez
05-23-2013, 10:02 PM
I kind of suspect that the recognition is on the left/right/break connectors, and not on the backup light connector. I am going to test this if someone does not come up with a precise description of what the recognition entails... Al