Turn signal master switch assembly

I'm a newby here and have looked a little for past posts without much luck to answer the following question- how many of you have had to replace the entire master switch assembly to get your turn signals to work again?

I am about to install another switch cluster in my '05 and it's getting old. The first lasted to 70K and was replaced with a new one that went out in the same manner after another 15K miles. In the meantime I had rebuilt the original unit (not so simple...) so I reinstalled it. The 2nd unit was warranted and was replaced.... I reinstalled it after another 10K when my rebuilt switch began to fail. This one only lasted 3K. I rebuilt the original again and put it back in and was able to get the replaced replacement replaced, which I'll probably install tomorrow as the rebuilt rebuilt is only working if I hold the stalk just so and the temperature isn't between 25 and 36 degreed F.

The contacts for the switches in the assembly are all very small, and the two contacts that complete the turn signal circuits appear to just arc fail and corrode over with gunk. I think they probably have a factory coating of nickel ore similar on them to protect them from the contact/break arc when used, and I think by cleaning them I have removed this layer and that's why my repairs haven't lasted very long. All of the other switches in the cluster work just fine, and it isn't a relay issue- clearly it's a matter of the switch contacts not contacting.

Has anyone else had this problem, and if so, how did you resolve it? I'm getting pretty good at replacing the assembly but it floors me that the switches seem to be so fragile.

A-mr-F,
In the two years I've been wandering the Sprinter forums I don't recall the turn signal switch failure/replacement being highlighted as a common problem in the NAFTA Sprinters. There have been some needing to replace the switch, but not enough to call it an epidemic as I recall.

Some guesses. Is your Sprinter wired for trailer lights? Perhaps something in added wiring has increased the loads on the contacts? Is it possible you have an intermittent ground or short in your wiring harness? There have been reports of wire harnesses chafing under the dash near the steering column. I believe there have even been some specific areas to watch for mentioned in some posts. Are there any electrical symptoms that may indicate harness problems? Any unexplained fuse failures?

Sorry I can't offer more information. Hope this does some good. AP/vic

My van has the factory trailer hitch and wiring- the switch failures don't present themselves in a way to suggest there is proceeding electric fault. The contacts start to make a slight buzzing sound as they make and break contact as the contacts wear, and this is followed by the blinkers ceasing to function alltogather. If I move the stalk forcefully and hold it with a little more tension than it should require I can put enough pressure on the contacts to keep them in contact and make the signals work. The stalk works a cam that pushes a small plastic push-rod that closes the contacts. The last time I rebuilt the switch unit I made a small rise in the contactor reed to allow it to push the contacts together with a little more oomph- but this was only successful for a time.

I'll have to think about outside causes- I can see if there was an excessive amperage draw on the signals how it might cause there to be more wear on the contacts- except that load should be getting carried by the flasher relay and not the switch.

Perhaps I should replace the relay when I replace the switch- I can envision how a fault in the relay coil might increase the load through the switch and still allow the system to function.

Hmmmm.......

Hey MrFixit

I did have a failure on my assembly at 85K, and while on this site (shameless plug) I did come across some helpful suggestions. Though my problem did turn out to be the Turn switch assembly someone noted the fuse holder assembly may be at fault. I ended up taking mine apart to make sure it didn't have any of the cracking problems where blinker relay plugs into the holder it at times breaks and requires some soldering. This maybe another spot to check for you!

Quick sidebar: I also tore my blinker assembly apart to see if it was just gunk and when I popped it apart and the internal junk fell on the floor I almost puked I was able to put it back together and make it work long enough to go buy another for 150.00 which I expected to be much higher.

amazingmrfixit said:

...

Perhaps I should replace the relay when I replace the switch- I can envision how a fault in the relay coil might increase the load through the switch and still allow the system to function.

Hmmmm.......

Click to expand...

Amazingmrfixit,
Good point about the relay and contacts load. It should be minimal. Trailer wiring wouldn't come into it. I hadn't thought it all the way the through last night.

I believe there are identical relays used. A place to start might be to compare coil resistance on similar relays. Please keep us informed if you trace down the cause. AP/vic

PS- As you say you've been getting better at the switch removal, a detailed procedure for the switch removal in the Write-ups would be a good addition to our knowledge base. I did one for the OM647 water pump replacement.

https://sprinter-source.com/forums/showthread.php?t=6228

Other people have also contributed great Write-ups. The reward is that it's nice to get the feedback from people who have used it.

That said, there may be one for the switch already. I don't remember seeing one though.

Perhaps I should replace the relay when I replace the switch- I can envision how a fault in the relay coil might increase the load through the switch and still allow the system to function.

Hmmmm.......[/QUOTE]

I think you are headed in the right direction. Check connections at the relay and any other harness connections between the switch and the relay. Resistance lowers voltage. Lower voltage means higher amperage. Over amperage or current is what burns contacts. In such a light control circuit an amp or two would do it. Let us know if you find any corrosion or loose connections.

Chris

A follow up and an apparent solution:

I replaced the multifunction switch with a new unit and at the same time replaced the turn signal relay located on the underside of the steering column. I've put another 25K on the van since and there has been none of the arcing/buzzing that proceeded the previous failures of the multifunction assembly. I am pretty sure now the original relay was drawing too much current (I did not ohm it before tossing it out- my mistake) and causing the very tiny contacts in the Mf switch to arc and fail.

So- if you find your turn signals have failed and the MF switch is to be replaced, be sure to install a new relay at the same time, as it is very likely to have produced the failure in the first place.

The plug in connection pins for the flasher relay are the same poor design as the fuse connections. Maybe by removing/re-installing the relay you helped establish a better connection? Coil resistance in a 12 volt relay is not likely to change. Shorts between windings which may lower resistance and increase load are not common with low voltage components... but, you never know? vic

amazingmrfixit said:

A follow up and an apparent solution:

I replaced the multifunction switch with a new unit and at the same time replaced the turn signal relay located on the underside of the steering column. I've put another 25K on the van since and there has been none of the arcing/buzzing that proceeded the previous failures of the multifunction assembly. I am pretty sure now the original relay was drawing too much current (I did not ohm it before tossing it out- my mistake) and causing the very tiny contacts in the Mf switch to arc and fail.

So- if you find your turn signals have failed and the MF switch is to be replaced, be sure to install a new relay at the same time, as it is very likely to have produced the failure in the first place.

Click to expand...

Aqua Puttana said:

The plug in connection pins for the flasher relay are the same poor design as the fuse connections. Maybe by removing/re-installing the relay you helped establish a better connection? Coil resistance in a 12 volt relay is not likely to change. Shorts between windings which may lower resistance and increase load are not common with low voltage components... but, you never know? vic

Click to expand...

That's a realistic possibility, but I did note the pins on the relay I removed were clean and showed no signs of arcing. Why I didn't ohm the silly thing when I had it on the bench along with the replacement is beyond me- I'll blame it on being over 40 and leave it at that. I "rebuilt" two of the master switches that I had failed and both of them had cratered and smoked contacts for the turn signals- which I thought must be related to an excessive load problem. All of the other contacts in the switch were fine- and there are a LOT of them. I'm hoping this fix is going to last, and as I had 5 failures before I bothered to swap out the relay I'm inclined to assume the relay had something to do with it.

Time will tell, I suppose.

Mrfixit.
The cct for the blinkers shows the power going to the relay and then to the blinker switch so the relay can not be the problem. The current for the globes goes through the switch. If the damage was only on one side it would most likely be a faulty light but if is on both sides it has to be a faulty design of the trailer wiring. I have done lots of miles in Sprinters and have never had a switch fail. Eric.

Well, rats.

Both of the contacts for the turn signals (there is a left and right contact) have been fried in the switches I took apart, and my Sprinter does have the factory installed hitch and wiring. It had been suggested that the cause might be a faulty converter box for the trailer wiring- but I can't locate such an item.

My first master switch took some 70K to poop out, so it's not out of the question the issue is corrosion/wear related. Do I wait for my present switch to fail or keep looking for a cause?

If I keep looking, where do I venture next?

amazingmrfixit said:

Well, rats.

...
and my Sprinter does have the factory installed hitch and wiring.
...

If I keep looking, where do I venture next?

Click to expand...

Maybe this will help?


https://sprinter-source.com/forums/showthread.php?t=7505

vic

P.S. - Still goin' strong OrioN!!!

Mr fix it.
Vic's PDF is the wrong model. Your unit has relays somewhere, you must be able to trace the wire back from the hitch to the relay box, If not just remove your rear lights and cut the wires to the the relay box. The factory wires are protected with a black cloth, the hitch wires are most likely covered with plastic. If you pull the large plastic bung behind the rear wheels and reach inside the cavity you must find the box. Comments from others indicate water in the relays is the likely cause of your switch problem. Eric.

Mrfixit
I have a turn signal master switch assembly to install. You mentioned you were getting pretty good at this. I am concerned with the airbag in the steering column when replacing the switch. Do you have any cautions or helpful suggestions before I attempt this? Cliff

cliff normand said:

Mrfixit
I have a turn signal master switch assembly to install. You mentioned you were getting pretty good at this. I am concerned with the airbag in the steering column when replacing the switch. Do you have any cautions or helpful suggestions before I attempt this? Cliff

Click to expand...

Yes please Mr Fixit. A write up on MFS switch replacement would be super helpful right now. or - Maybe you can do one, Cliff?

Airbags are nothing to fear. Like a gun, just learn how to handle them and treat them with respect. Whenever working on anything electrical, disconnect the battery.

OK- long term follow up:

I have since experienced the dreaded non-working turn signal problem another three times. However- in the last three instances I have simply swapped out the turn signal relay and the problem has resolved. Each time I did this it was at the first sign that the turn signals were beginning to fail: I can only hope the contacts in the master switch assembly are still in reasonable condition. If anyone else is experiencing a turn signal failure (even if it only is to one side and not the other) try replacing the relay FIRST as it's super easy and reasonably cheap. In my case, the relays seem to have about a 6 month life and begin to show signs of an issue on humid days with temps in the 40's.

As for changing the master switch... this is from memory, so bear with me:

1) Disconnect the battery. Have a soda. Do a crossword puzzle. Wait 15min or more for the airbag system to safety.

2) Remove the airbag by unscrewing the torx fasteners from the backside of the steering wheel. The airbag can be unplugged from it's wiring via the center connector (I seem to recall it's yellow). It'll be a pain to remove- but it is a press fit.

3) Disconnect horn wiring from the steering wheel and remove the center bolt holding the steering wheel in place. (10mm allen, I think) Remove wheel, snaking the wires out through the wheel- they will JUST fit.

4) Remove the cover from the topside of the steering column- a stubby #2 philips is needed here.

5) Remove the cover from the underside of the column and unbolt the fuse block. Pull the fuse block off of the multi pin block on the underside of the master switch.

6) Remove the steering angle sensor taking care to see how it is oriented, and let it dangle. Unscrew the two remaining philips screws that are holding the masterswitch in place (these are hard to see and you have to have a screwdriver that can reach through the access hole to get to them). If you have cruise control the additional wires will have to be followed and unhooked.

7) if I haven't forgotten anything, the master switch should now lift off out over the steering shaft.

One note- the 10mm bolt that holds the fuseblock to the masterswitch threads into a captured nut in the switch, and if you over tighten it the nut will spin and you will have a HELL of a time removing it in the future. Be careful not to over tighten.

Whoever does this next please feel free to edit my instructions as required.

Whoever does this next please take and post photos!

I too am experiencing the dreaded turn signal flicker failure. I might have tracked it's demise to a friend driving my van, and leaving the parking lights on, but somehow also had the turn signal turned to the left or right. The next morning, I came down, baffled to find one side of my van lit up. Not blinking, just lit up.

Since I never use the parking lights, I wonder if the blinkers fried the relay. It's still slowly dying... I usually get one blink before it goes out now.

Mrfixit, are you saying you replace the signal relay with a new one every 15k or so??? Are we talking about the same item, costs about $125?

Matt

My parts guy was getting me the relays for about $15 per... part number #003 542 02 19. The relay is located under the steering column in the fuse block- remove the fuse cover and it's right there. There are two relays located right next to each-other, and I forget which one is for the turn signals- I usually turn the signals on while touching the back of the relay and feel which one "Ticks". One of these days I'll just mark it with a pen!

Uncle Google shows these guys having the relay for $14:
http://www.everythingbenz.com/z/part/0035420219-mercedes-multi-purpose-relay