Reply
 
Thread Tools Search this Thread Display Modes
 
Old 08-11-2012, 06:20 PM   #15
2 Rivet Member
 
ModernVista's Avatar
 
2016 28' International
Los Angeles , California
Join Date: Jul 2012
Posts: 66
Quote:
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
__________________

__________________
ModernVista is offline   Reply With Quote
Old 09-10-2012, 11:00 AM   #16
4 Rivet Member
 
ddruker's Avatar
 
2000 27' Safari
Palo Alto , California
Join Date: Apr 2012
Posts: 260
Images: 1
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.
Attached Files
File Type: pdf Trailer Modification for LED lighting 164.pdf (10.4 KB, 99 views)
__________________

__________________
ddruker is offline   Reply With Quote
Old 09-11-2012, 07:53 PM   #17
4 Rivet Member
 
ddruker's Avatar
 
2000 27' Safari
Palo Alto , California
Join Date: Apr 2012
Posts: 260
Images: 1
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 ?
Attached Thumbnails
Click image for larger version

Name:	IMG_20120911_152423.jpg
Views:	68
Size:	222.1 KB
ID:	168031   Click image for larger version

Name:	IMG_20120911_151736.jpg
Views:	85
Size:	259.2 KB
ID:	168032  

__________________
ddruker is offline   Reply With Quote
Old 09-11-2012, 09:30 PM   #18
Rivet Master
 
dznf0g's Avatar

 
2007 30' Classic
Oswego , Illinois
Join Date: Jul 2010
Posts: 9,407
Images: 5
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
__________________
-Rich-

"If the women don't find you handsome, they should at least find you handy." - Red Green
dznf0g is online now   Reply With Quote
Old 09-11-2012, 09:51 PM   #19
Rivet Master

 
Southwestern , Ohio
Join Date: Nov 2006
Posts: 1,669
Quote:
Originally Posted by ddruker View Post
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.
.
__________________
Nuvite-F is offline   Reply With Quote
Old 09-16-2012, 12:29 PM   #20
4 Rivet Member
 
ddruker's Avatar
 
2000 27' Safari
Palo Alto , California
Join Date: Apr 2012
Posts: 260
Images: 1
I'm unhappy to report that the 220 Ohm resistors installed as described above did not solve the problem - back to the drawing board...
__________________
ddruker is offline   Reply With Quote
Old 09-17-2012, 11:24 PM   #21
Rivet Master
Commercial Member
 
Dan@LED4RV's Avatar
 
Currently Looking...
Denton , North Carolina
Join Date: Jul 2006
Posts: 695
direct in line

Quote:
Originally Posted by ddruker View Post
I'm unhappy to report that the 220 Ohm resistors installed as described above did not solve the problem - back to the drawing board...
Did you hook the unit up (Put it on the ball) and pull it around a little? You may have a good ground on your unit and a good ground on your MB but are they together?

The PDF file from MB shows the resistors going to ground. I'm sure they know what their doing but with the wrong values, or a bad ground.

If you used the resistors direct in-line it would lesson the brightness of the LEDs.

Another thing I would try is getting a jumper wire and running it to the ground inside the trailer's plug and directly to the battery of the MB. Just let the wire lay on the floor to see if it helps.

The above suggestions are with the resistors still in place
__________________

__________________
Dan Brown
Denton NC
Dan@LED4RV is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
newbie with a tow question echo44 Tow Vehicles 47 06-12-2013 05:42 PM
2012 Edition: LED lighting upgrades Jammer Lights - Interior & Exterior 11 03-16-2012 12:36 AM
Newbie propane question zlee On The Road... 21 03-13-2012 07:43 AM
'73 tradewind gaucho slides question, help! moparjohn General Interior Topics 2 03-12-2012 08:18 AM
really dumb newbie question! carolinagirl General Repair Forum 10 03-11-2012 03:09 PM


Virginia Campgrounds

Reviews provided by




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 07:22 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.