High beams ON, Left Turn Signal On --> Headlights then go dark ???

[RicardoD]

Anybody run into this?

Headlights ON, High Beams On, and then active your Left Turn Signal and all headlights go DARK. Doesn't happen if I activate right turn signal. If I exit Left Turn Signal all headlights / high beams come back on. Scares the crap out of me when this happens.

Is this a known issue and quick fix? Not sure where to start on this problem.

 

[gsxr]

Wild guesses: Either the combination switch, or (less likely) the bulb-out module since all lighting power is routed through that monster relay behind the fuse box.

Never heard of this exact scenario though.

 

[nocfn]

I had a c126 issue where the combo switch insulation came off inside the steering column. I replaced the switch and a bad relay and never had an issue since. Light switch and ignition switch were also changed the same year, they were both original and worn.

 

[RicardoD]

The way it behaves it does make sense that something in the combo switch is off.

Combo switch on my 1994 model is: 1245402044 for about ~ $120 at mboemparts.com
- that doesn't look too fun to change

Anybody have the headlight control module part number? I think it is 78 or 101 in the EPC snapshot

 

[gsxr]

Ricardo, the bulb-out module is #101, MB p/n 126-542-01-32. Oddly, it's showing NLA at the RevParts sites, but MB Classic shows "available". I wouldn't buy a new one though - they are rare failures, and shared across all 124 & 126 chassis. Lots of used ones available cheap. If available new it is likely $300+. My money is on the combo switch, if you are going to gamble on something.

 

[RicardoD]

Some quick googling came up with this, doesn't look too bad

 

[RicardoD]

This isn't a problem that encounter often, and I know now to not turn signal left with my brights on. But just a sign that perhaps my turn signal combo switch is on its way out. Hmmm... I will think it over and of course write up a detailed how to if I ever get to this.

 

[gerryvz]

The combo switch isn't bad. I replaced it on my former E320 wagon many years ago.

Essentially to do this, from my memory:

0.5) Extend the steering wheel outward as far as it will go. Turn key to release steering wheel from steering lock.

1) Disconnect the battery.

2) Disconnect the red airbag connector behind the passenger-side footwell

3) Remove the two screws that hold the airbag to the wheel, from behind. I believe they generally use Torx bits.

4) Pull airbag off of wheel and disconnect airbag electrical connector at wheel.

5) Mark steering wheel position on splines with a Sharpie(TM) marker

6) Use a 10mm Allen socket (3/8" drive) to loosen bolt at center of steering wheel. Note that you WILL need a helper to hold the steering wheel so that it does not hit (and possibly break) the "lock." DO NOT use the "lock" to hold the wheel -- use a strong helper to hold it. A breaker bar or long handled (18"+) socket handle is advisable to make this step easier.

7) Pull steering wheel straight off of splined hub.

8) Undo the screws that attach the turn signal stalk mechanism to the steering wheel. Note that the cruise control stalk (IIRC) slides into the base of the turn signal stalk -- it is a separate mechanism.

9) Remove the lower dash cover next to the steering wheel, and unplug the dense electrical connector.

10) Remove turn signal lever mechanism from car.

11) Plug in replacement turn signal lever mechanism under dash, after routing cable from steering wheel area to proper location.

12) Re-assemble turn signal mechanism. Procedure is the reverse of removal.

It should take you well under an hour to do all of this, taking your time and taking care.

 

[gsxr]

Some quick googling came up with this, doesn't look too bad

Ricardo, note that video is showing a non-airbag car. You'll need to use Torx drivers to unscrew the airbag from the rear, not pry the cover off as shown in that video.

Also, if you have a 1/2" impact wench, use that for the steering wheel center bolt. MUCH easier than messing with a breaker bar.

Finally, your 1994 E500 will have a contact spiral instead of the older contact ring with brushes. DO NOT disassemble the contact spiral! It will unbolt and some out in 1 piece.

 

[RicardoD]

Thanks guys, combo switch ordered!

 

[RicardoD]

This beautiful new part came today. When I get around to doing this one I will make a HOW-TO: based upon the helpful tips on this thread.

 

[RicardoD]

So excited this morning, time to change the combo switch and I get stuck at Gerry's step 3

3) Remove the two screws that hold the airbag to the wheel, from behind. I believe they generally use Torx bits.

Those torx bolts are at least 2 inches (52mm) deep into he back of the steering wheel. And guess what kind of torx bits I have? Big fat ones for 1/4" drive socket and they don't fit in that hole. Then I have a multi-bit tool but the extension is too fat. Then I also have a tiny bit set screwdriver but the bits are not big enough. My thing is too big to fit into the hole!!!

Time to find something at Amazon.

 

[gerryvz]

You will need a T-27 size for these bolts. Look on eBay for an appropriate tool (or factory tool) that will work.

I use a Craftsman T-27 screwdriver for this job, FYI. So, your local Sears/Craftsman/Ace Hardware outlet may have it in stock.

I have successfully, but inconsistently, used Allen keys in the past.

 

[gsxr]

Factory tool shown below. I'm not sure of the size but I thought a standrd size (T25 or T30) would work...?

Still only $10 from Napster:

Socket 126-589-00-10-00 | MB OEM Parts

126-589-00-10-00 - Socket

www.mboemparts.com

 

[RicardoD]

Thanks Gerry, I found a Torx bit set, including T-27, 3" (75mm) long on eBay which is perfect. You have about 6 inches (153mm) behind the steering wheel to work with steering wheel extended to max position.

Dave, the Mercedes one looks about 75mm long as well. Need a bit more than 50mm. The eBay set was only $12

 

[RicardoD]

One more thing. The forum is amazing. I will never be able to get rid of this car, not that I want to, but realizing I am stuck with it for life unless I get into an accident. This group will keep my E500 running forever.

 

[gsxr]

Forgot to mention, a normal Torx driver will usually work if you rotate the steering wheel so the fastener being loosened is at the 6-o'clock position... and extend the telescoping steering wheel as well.

 

[geraniumtr]

Ricardo, I've done this job and was going to post a few hints but procrastinated. In my 94 E320 its a T30 for the two airbag screws. I just ran out and double checked. The T30 fits. You need to use a single Torx key without a handle. The set I have are bare metal with a 90 degree bend at one end. A driver with a handle is too fat to work in the confined space.

Also when reinstalling the air bag follow FSM 91-660 carefully or your steering wheel will squeak when turned. BTDT.

One more hint. Before removing the hood release handle-- pop the hood open. This will give you a little slack in the wire cable making installation a little easier.

Regards,

Peter Weissman

 

[RicardoD]

Thx, Peter, the set I ordered includes a T-30. I am documented this for another HOW-to to collect all the words of wisdom together for everyone else.

 

[gerryvz]

A Torx screwdriver will work just fine, as long as you turn the wheel to the 6PM position (and extend it out all the way). I just used it not two weekends ago on my G-wagen. I used the T-27, but I also have a T-30.

 

[RicardoD]

Got a T-27 screwdriver from my neighbor (another car nut) so back in business this weekend!

 

[RicardoD]

YES!!!! Problem FIXED!!!! Love this forum.

Finally, your 1994 E500 will have a contact spiral instead of the older contact ring with brushes. DO NOT disassemble the contact spiral! It will unbolt and some out in 1 piece.

Dave, you don't say? You mean you will end up with an unspooled ribbon cable all over yourself?

(Should have paid more attention to the comment. My HOW-To on this will prevent other hacks for making the same mistake )

 

[gerryvz]

Did the T-27 work OK?

 

[RicardoD]

YES, T-27 worked like a charm

 

[RicardoD]

To close this out T-30 is the correct size for the airbag bolts even though T-27 will work. Confirmed after I received my Torx bit set today.