LED Lighting question

[CO Airstream]

Has Airstream developed or does anyone know of a solution for getting my LED's to work on my new 2012 Flying Cloud with my Mercedes-Benz 350? I am familiar with the issue and the work around with an in-line bulb or a resister in the light fixture, but i would prefer not to have to pull apart the tail light fixture on my brand new trailer. Is there a plug that you can fit between the tow package socket and the trailer plug?

[Jammer]

Welcome to the forums.

What LEDs have you added? Inside? Outside? Running lights?

[Friday]

Is it a polarity issue? There are aftermarket LED's that have built-in polarity correction...

[CO Airstream]

Originally Posted by Friday

Is it a polarity issue? There are aftermarket LED's that have built-in polarity correction...

They are the factory lights. I think I am looking for a 7 to 7 adapter that has a built in resistor that Valley used to make but are not currently available. If anyone knows where I can get one I would appreciate it. Thanks...

[vinstream]

I made one that plugs in between the TV and the Trailer at the 7 way plug, I pull with a Touareg and have found that German cars have this problem over other brands. I have not seen any unit like the one I made on the market. I have posted on here before about this problem but seams to not be an issue with others outside of German made TV's. I would think that Airstream should step up and fix the issue and have a fix in the trailer you just spent a lot of $$$ on. If they are going to uses LED lighting in these systems then they should support any and all TV's it just seams silly to me that they don't.

[Friday]

I'm not sure I understand what the issue is... It's a standard plug, so if the signal coming out doesn't work, it's not Airstream's fault.

Anyway, I've read that VW makes an adaptor as well as they have the same issue.

http://www.airforums.com/forums/f464...s-77768-2.html

[xrvr]

Yes, I think VW can help. jim

[Nuvite-F]

Originally Posted by vinstream

I made one that plugs in between the TV and the Trailer at the 7 way plug, I pull with a Touareg and have found that German cars have this problem over other brands. I have not seen any unit like the one I made on the market. I have posted on here before about this problem but seams to not be an issue with others outside of German made TV's. I would think that Airstream should step up and fix the issue and have a fix in the trailer you just spent a lot of $$$ on. If they are going to uses LED lighting in these systems then they should support any and all TV's it just seams silly to me that they don't.

Can anyone tell the rest of us exactly what the problem is?

Let me guess at a couple of possibilities. The fact that some have referred to a "resistor" leads me to wonder if the Mercedes 350 has an electrical system using a higher voltage than 12 V, such as 24 V.

Or, do some of these cars detect the current drawn by the trailer lights and provide a failure indication if the lights are not drawing a certain amount of current, which LEDs might not, even if they were working correctly?

I imagine the problem would be simple enough to solve if we knew what it was!
.

[dznf0g]

If Op is taliking about converting to LEDs for tail, brake and turn signals, Many cars and trucks have either the flasher or body control module looking at "x" amount of resistance across bulb filiments. This allows for the indication of a burned out bulb. If that is the issue, SuperbrightLEDs.com has rather inexpensive resistors to fake out the system on the cars. I have them on one of my vehicles. Imports seem to require them more commonly than domestics, but My son's Cobalt SS required them.

[AirsDream]

Yes, it's not clear what is the problem, but I strongly suspect that it's the resistance issue. My M-B and BMW both have "bulb failure" sensors that look at resistance as a measure of lamp performance. And they have sid-to-side comparisons as well, and are sensitive enough that sometimes even a functioning but lower-current-draw-than-the-other-side will tlrigger the sensor.

And if this is correct, there are two obvious solutions: a.) get the SuperBright LEDs resistor package, or b.) keep the running lights as incandescents and change out only the interior lighting, which tends to be the battery-drainer when parked anyway

[dznf0g]

In addition, if the TV is "monitoring" the trailer running/tail/brakelights by sensing an umbilical connection, it could be the same issue as a TV LED conversion. Some newer vehicles do monitor the TV trailer connector harness through a body control module. If that's the case and MB is looking for more resistence AND they don't have a factory work around, then I think the added resistor is your only option. I gather you do have a factory AS LED tail light configuration....correct?

[Dan@LED4RV]

Originally Posted by CO Airstream

Has Airstream developed or does anyone know of a solution for getting my LED's to work on my new 2012 Flying Cloud with my Mercedes-Benz 350? I am familiar with the issue and the work around with an in-line bulb or a resister in the light fixture, but i would prefer not to have to pull apart the tail light fixture on my brand new trailer. Is there a plug that you can fit between the tow package socket and the trailer plug?

Mercedes-Benz is funny about their warranty when you have other companies work on it. FYI, fixing the Airstream to work with the Benz as is is always best! I see this is the way your going but just wanted to explain for others following this thread.

I have never heard of an adapter.

A fix I saw that worked very well was finding the STT wires under the dinette (it was a small unit and I trust yours is too) and attach light sockets with bulbs. It allows enough power to get your lights to work. These lights under the dinette were not allowed to touch any thing.

[Wayne&Sam]

I'm pretty sure Andrew T at canamrv.ca worked it out for others. I think there is a part that plugs between the vehicle and the 7-way plug that solves it.

[CO Airstream]

Thanks for all of your input. We solved the problem by replacing the LED's in the running lamps with incandesant bulbs. This was the recomended fix by AS, thanks again for your input...

[ModernVista]

Originally Posted by CO Airstream

Thanks for all of your input. We solved the problem by replacing the LED's in the running lamps with incandesant bulbs. This was the recomended fix by AS, thanks again for your input...

First post!

I wanted to post this so other Cayenne, Toureg, and other european TVs (Mercedes) know what the problem is.

I have a Prodigy RF and a 2013 Airstream with a 2012 Cayenne as the tow vehicle.
The Cayenne has smart monitoring of the trailer system via the 7 pole plug. This means that it pulses the lights and by doing so it can detect a short, a failed light or other failure. However, this system is designed for a higher amp draw than an LED system provides.

Because the Prodigy RF requires the TT not to be connected for the pairing process (process where the remote brake controller finds the brain) but it requires power to pair, it fails on the cayenne to connect. This is due to the cayenne not detecting a draw, and not providing 12 volt power to the plug and thus the prodigy brain.

Without any modification it is impossible for the cayenne to pair the prodigy rf brake system. However, you can pair the system on another vehicle and then use it.

I managed to get it to pair on someone else's tow vehicle and all seemed to work. Sort of.
On my vehicle the power draw of the TT to the cayenne is clearly borderline as it connects and disconnects the 12v to the plug periodically and even occasionally throws errors in the system. So i Called tekonsha, makers of the prodigy.

The solution per tekonsha is to find a 7 pole to 7 pole adapter which emulates the draw of an incandescent ( these apparently exist but I have not been able to find one) or to wire in a resister or to add incandescent bulbs or to forego the cayenne system and wire something that may void warranty.

I haven't done anything yet, and was searching for the best answer, thus found this post. So my question, where can I find this plug adapter, or as the person above did, how do i 'upgrade' my 2013 airstream to incandescent lights? Is this something i have to take to the dealer? Would prefer to do myself, if possible.

Cheers

Chris

[ddruker]

I just upgraded my Safari to LED taillights and ran into the same problem with my Mercedes GL 350. Pretty frustrating for a TV that has LED lighting.

Things are fine during the day, but whenever the headlights go on, all of the running lights and the tail lights on the trailer flash rapidly. The brake lights do come on and stay on when pressing the brake pedal.

I spoke with a factory tech as my local dealer is clueless in all things towing related. The problem is that up to and through the 2012 model year, the root of the problem is that the Mercedes GL computer simply doesn't know about LED trailer lights.

When it senses the trailer umbilical is plugged in, and then when the headlights go on, it sends a series of diagnostic pulses to make sure the trailer tail lights are ok. It is expecting to see the resistance profile of incandescent bulbs only in the tail light circuit.

Since the LED bulbs look very different electrically, the computer thinks that there is a fault in the trailer's tail light / brake light system.

And to make sure you know about it, the GL rapidly and continuously flashes all of the trailer lamps - the running lamps, the tail lamps, etc - and even the collision avoidance triangles in the GL mirrors, as a warning that something is wrong.

According to MB USA, the fix is to install two 220 Ohm, minimum 1.5 Watt resistor - one each in parallel with both the left turn/stop and right turn stop circuits. You can do this anywhere in the circuit - using an adapter at the trailer plug, in your taillight fixtures, or anywhere in between. Mercedes actually makes an trailer plug adapter - but only for four and five pin trailers - and get this - they want to charge more than $200 for it. For what nets out to two 75 cent resistors.

They say this will be fixed in the 2013 model year and the new GL will understand LED trailer lights.

Attached is PDF Mercedes sends out on this... Pretty obviously hacked together by somebody here as opposed to a formal data sheet out of Germany.

All of this (and their silence on weight distribution, and their wimpy tongue weight specs) together do not give a ton of confidence the Germans are spending time to really understand the towing market here in the USA, beyond marketing that their vehicles have a 7,500 pound towing capacity.

[ddruker]

Just for reference sake - here are pictures and measurements of the fix. It took about 30 minutes and cost less than one dollar.

Mercedes recommends installing a 220 Ohm, 1.5 Watt or better resistor in parallel with each of the turn / brake light circuits.

First some physics - when you install resistors in parallel with an existing load, you lower the resistance of the overall circuit. The formula is 1/Rtotal = 1/R1 + 1/R2.

I measured the resistance of each brake light circuit from the Airstream's trailer connector using a fluke digital multi-meter.

Both left and right turn / stop circuits measured 2.2 Ohms with incandescent bulbs installed, and 29.8 ohms with LED bulbs in place. This implies each of the two LED bulbs on each side has roughly 60 Ohms of resistance, vs. roughly 4 ohms for an incandescent bulb. For comparison, the backup lamp circuit measured 4.2 Ohms, and the running light circuit 1.8 Ohms. The estimates for the bulbs above are all rough - I was too lazy to measure bulb resistance directly; all of the measurements above also reflect the resistance of the trailer wiring.

So using the formula for calculating parallel resistance, when installing a 220 Ohm resistor in parallel with a 29.8 Ohm existing load, 1 / Rtotal = 1/220 + 1/29.8 = 26.3 Ohms. So we expect each turn / stop circuit to measure about 26.3 Ohms when the repair is completed.

The first picture attached shows a 220 Ohm, 5 Watt, 5% tolerance, metal wound resistor. A pack of two of these cost 89 cents from our local Fry's Electronics.

The second picture shows the resistor in the middle of being installed. For ease, I chose to install inside the tail light fixture.

First remove the outer tailight lens. Then gently pull out the reflector. You'll see three wires - a white ground wire attached to the back of the reflector, and two wires (in my case yellow and brown) attached to the bulb socket.

The only trick is that you have to determine which of the two wires feeding the bulb is the turn / stop signal. I did this by connecting a wire to my battery and then to the appropriate pin on the trailer plug. It turned out the yellow wires are for the turn / stop signal.

As you can see in the picture - I simply removed a bit of insulation from the yellow wire with a hobby knife. Then I connected the resistor between the exposed copper wire and the white ground on the back of the reflector cup. The picture is before soldering and covering the connections with liquid electrical tape.

After screwing everything back together, each circuit now measures 26.8 Ohms - which is close enough to the expected value that it shows the resistors are correctly installed.

Final test is to apply 12V to each of the brake / stop circuits - and both sides illuminate correctly.

Later this week I will have a chance to hook up at night again and verify the fix actually stops the GL from flashing all the lights.

So what is actually going on here? I have no idea. The resistance numbers I measured above are for the incandescent bulbs when cold. When they are illuminated and get hot their resistance will increase - but only to 7 or 8 ohms per bulb. So the 220W resistor is not trying to make the whole circuit look like it has the resistance profile of incandescent circuit. Anyone know what the tow vehicle is actually trying to measure ?

[dznf0g]

Wish I had seen this thread earlier. This has been an issue with many Japanese and German cars for a long time.

This is from Superbright LEDs.com. I had to use on a Suzuki many yaers ago.

http://www.superbrightleds.com/pdfs/...istor_info.pdf

[Nuvite-F]

Originally Posted by ddruker

So what is actually going on here? I have no idea. The resistance numbers I measured above are for the incandescent bulbs when cold. When they are illuminated and get hot their resistance will increase - but only to 7 or 8 ohms per bulb. So the 220W resistor is not trying to make the whole circuit look like it has the resistance profile of incandescent circuit. Anyone know what the tow vehicle is actually trying to measure ?

Resistance doesn't tell the whole story since the LED is a nonlinear device. Below a certain threshold voltage (1 or 2 volts) it doesn't conduct at all.

So I can speculate that the Mercedes microcomputer might ping the lamp circuit with a low voltage pulse--not enough to light the bulb it expects to see--doesn't see any current flow, and concludes that the circuit is open.

As I said this is only speculation--I have no idea what M-B actually does--but it would account for the behavior you see.
.

[ddruker]

I'm unhappy to report that the 220 Ohm resistors installed as described above did not solve the problem - back to the drawing board...