Headlight failure on 2013 VIA

[thataway4]

I have a 2013 Winnebago VIA, on the Sprinter 3500 chassis. Recently the passenger side headlight was not working. I have taken the unit to local "Import mechanic" who works on Sprinters and other Mercedes. He put a new bulb in. It flashed 6 to 8 times and then stayed "out". Tried second bulb. Same problem. If you turn off the lights, and check again in a few minutes the same issue. The fog light, and parking lights, turn signal all work on the right. Headlights and all work on the left.

He says "short to ground". Was going to "hard wire in a new ground". He has had the unit for 3 working days, and says he is still working on it--but he believes it needs a new "Body Control module". I have noted that in some threads, apparently people have used the wrong light bulb--I don't know what one he is using, but apparently it is a common bulb. He had several in stock.

I have reviewed the wiring diagram and body control module schematics on the "diy Sprinter UK" site (figure 9 and 34). I am a ham radio operator, have a fair background in electrics and electroncics--but am 83 years old, and cannot physically do work on my own vehicles because of physical disabilities).

The mechanic now thinks it needs a new "Body Control Module"--and the cost of the repair and module will be in the $900 range.

Thank you in advance for any advice you can give me.

Bob Austin
Pensacola, Fl,
2013 Sprinter 3500 Van conversion by Winnebago VIA.

[Morich]

With an electronics background, what does it leave you thinking if a mechanic is not sure if he has a ground or not?
Personal opinion of course, but when a fellow is unsure about finding a ground, I'm not inclined to invest $900 on a fix without checking other places first. Got any other options for repair?

[thataway4]

Originally Posted by Morich

With an electronics background, what does it leave you thinking if a mechanic is not sure if he has a ground or not?
Personal opinion of course, but when a fellow is unsure about finding a ground, I'm not inclined to invest $900 on a fix without checking other places first. Got any other options for repair?

Morich,
Thank you.
Yes, my instinct, is to pay him for "what has been done"--and go elsewhere. The other option is the Mercedes dealer.

I was wondering if there was some quirk of these headlights because there are "Mercedes"--other than a simple relay. From the circuit diagram, the relay function seems to be in the Body control module. There are separate outputs for passenger and driver side. When a light heats up, flashes off, then cools, it would make sense that there is some thermal contact issue here....where is the question.

Bob

[Morich]

As a former electron guy myself, I'm surprised and often wonder why things seem to be designed to fully use all the outputs from a chip, rather than keeping simple and the minimum. Two different outputs for left and right headlights seems to be one way to make something simple, too complex! What are we designed to get? A car with headlights that "wink"?
I'm glad you checked the drawings to find that before I guessed that it would be one single circuit!
And I do fully agree that is does sound like a thermal problem with the board. Something as simple as the current draw heats a solder joint but those seem to go open when cool rather than when heated, so perhaps a small bow forms in the board when warm?
The tech may be fully on the right track to replace the board. Are these LED headlights? Boards are nice for making things fast and cheap but they certainly are not easy to sort out faults, short of trial and error replacements which you and I often have to pay for the errors! The heating could just as easily be where the bulb plugs in as at the board.
Short on any more ideas to try, though.

[thataway4]

Morich, the lights are halogen bulbs.

[Morich]

Originally Posted by thataway4

Morich, the lights are halogen bulbs.

Just letting my mind wander around and thinking if there was some type of circuit near the base of LED bulbs but that is not true for halogen.
Halogen get hot but if there is no circuit board, it doesn't mean much.
Another dead end thought!

[AlanO]

Have your mechanic check the front SAM. A failure (usually) due to water intrusion can cause any number of electrical failures. The outputs are readable on the CAN bus with the correct scan equipment

[thataway4]

AlanO, The Signal Acquisition Module was OK. It turned out to be a short in the actual headlight/turn signal/parking light unit. Replacing that solved the problem.
Thanks for the reply!