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There’s lots been written about the R170 rear lights. I’ve been there, done that.
I recommend you take the light assembly off the car. Only 3 nuts. You see the design is not MB’s finest hour. The earth plate is also the mounting plate and is a cadmium plated affair.
The bulbs are mounted using a spring contact which doubles as location and electrical connection.
The earth plate gets a little surface corrosion and the contact becomes poor. You then get
Heat that can melt the plastic or
Sparks that burn the plate away or
Just plain intermittent connection
The brake light goes first because it is repeatedly on/off and draws most current.
Treatment means cleaning with an abrasive. This might be a polish with a cutting compound (t cut), wire wool, wet and dry or a dremel with a grind stone.
Mine needed the last one.
Then repair the plate if needed. Mine had a hole which I filled with solder and smoothed off. You may need to use a conductive grease to stop new corrosion.
Then look at the spring contacts. Clean and bend for maximum pressure. If melting is evident, buy a new bulb holder.
Check all the bulbs while you’re in there. Look for corrosion or blackening glass or just bin the lot and fit new, quality bulbs.
Mines been fine for nine months.
Time is about an hour per side. Cost is zero to a few pounds (bucks) depending what’s on your shelf.
Cheers Neil


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keeps failing. Sharp rap and it works. Once. Bulb is fine. Anything I should know about passenger side stop light wiring ? Just a single filament bulb.
Likely, it's bad contact in the lamp assembly. Contact cleaner may help for a while. Removing,, cleaning with emery paper and possibly solder on top is a permanent fix. I use the tried and tested strategy of "once is never, twice is always" - so if problems comes back after contact cleaner takes it away (electronics variety may be better than WD40, here), removing and repairing the holder is better.

There are ways, with the inserts removed, to get dual reversing lights to work - if that is of any interest to you.
 

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Premium Member 2001 SLK320/2000 SLK230
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Discussion Starter #6
Sounds like the best thing is to switch to LED lights, they pull much less current. Am I correct that the stop lamps and backup lamps are 1154 and the tail & turn signal lamps are 1156. Suspect I need ones with the CanBus resistor.
 

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Administrator 2009 SLK 55 AMG/Founding Member 2006
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Owner's manual says

page 175

 

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Sounds like the best thing is to switch to LED lights, they pull much less current. Am I correct that the stop lamps and backup lamps are 1154 and the tail & turn signal lamps are 1156. Suspect I need ones with the CanBus resistor.


That would help with the heat created by poor contact but won’t help the poor contact. You need good, firm reliable contact with any bulb. No canbus on the R170 as far as I know.
Neil


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That would help with the heat created by poor contact but won’t help the poor contact. You need good, firm reliable contact with any bulb. No canbus on the R170 as far as I know.
Neil


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I had the same prob with mine (and it also had the recall done). Neil's solution is the best. I bought new bulb receptacles as well as they were in rough shape due to arcing. In addition, building up a good contact as outlined above takes care of it.
 

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Registered 2005 SLK55 AMG
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I have seen bulbs break the filament from vibration, start working again with a sharp rap to the housing that causes the filament to touch and then resistance heat sticks the two halves together until the next hard rap separates them again. Currently have a bulb on our Vacuum doing this exact thing that I do not care to fix. That bulb stays on, flashes, stays off depending on the walls you bump into.

Had this problem on a trail bike headlight as well, too much vibration broke the filament, didn't notice until I was 20 miles from home and it was starting to get dark, fortunately, I hit the housing, it started working and made it home before it failed totally.

But then, I am certain you have replaced the bulb and still have the problem. Contacts in the plug, ground connection, and possible break in the wiring, had all these problems at one time or another. Other than company cars, for a long time the newest car I had owned was 20 years old, with years of problems stored up in them.
 

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That would help with the heat created by poor contact but won’t help the poor contact. You need good, firm reliable contact with any bulb. No canbus on the R170 as far as I know.
Neil


Sent from my iPhone using Tapatalk
I had the same prob with mine (and it also had the recall done). Neil's solution is the best. I bought new bulb receptacles as well as they were in rough shape due to arcing. In addition, building up a good contact as outlined above takes care of it.
 

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Premium Member 2001 SLK320/2000 SLK230
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Discussion Starter #12
Yes have that (enlarged below):

Problem is that it shows four bulbs and my taillight has three single filament bulbs, all the same size, one amber coated (is that what NA means ?). It also shows 1154s which show as dual filament and all of mine are single filament.

Bulb makings are not normal, suspect European (eg. PA21498).

So thought it best to ask if anyone can recommend LEDs that work in the taillight of an R170 (facelift).

I have checked the normal resources just the answers have been inconsistent with my taillights.
 

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Premium Member 2001 SLK320/2000 SLK230
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Discussion Starter #14
Anyone in the US have the answer. BTW my owners manual says "USA Edition C 2001" but I just have four single filament bulbs, one amber. Three large (stop, backup, turn) and 1 smaller (67?) for taillights. While the 1154 mentioned in the manual for stop and backup (page 175) is dual filament so is evidently wrong.

The 67 is in a different place passenger vs driver which had me going for a bit.

Have looked on the bulbs themselves and those markings are different. e.g. P12498

However the manual says 21W for the three biggies (my oems are marked 21w) while an 1156 is the proper configuration but 26.9W and is brighter/hotter which may explain the heat issue if 1156s were used for P12498s

So would like to replace the biggies with LED but apparently the current is sensed by the computer (got a warning on dash when stop light was out) so would appreciate knowing what others have found to be a good CANBUS LED replacement if someone here has made the swap. YWTK.

So while the 5W 67 taillight is ok, I'd like to replace the biggies. Has anyone used these ?
 

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Anyone in the US have the answer. BTW my owners manual says "USA Edition C 2001" but I just have four single filament bulbs, one amber. Three large (stop, backup, turn) and 1 smaller (67?) for taillights. While the 1154 mentioned in the manual for stop and backup (page 175) is dual filament so is evidently wrong.

The 67 is in a different place passenger vs driver which had me going for a bit.

Have looked on the bulbs themselves and those markings are different. e.g. P12498

However the manual says 21W for the three biggies (my oems are marked 21w) while an 1156 is the proper configuration but 26.9W and is brighter/hotter which may explain the heat issue if 1156s were used for P12498s

So would like to replace the biggies with LED but apparently the current is sensed by the computer (got a warning on dash when stop light was out) so would appreciate knowing what others have found to be a good CANBUS LED replacement if someone here has made the swap. YWTK.

So while the 5W 67 taillight is ok, I'd like to replace the biggies. Has anyone used these ?
I have a facelift (2002) and have overhauled the lamp holders recently (due to indicated reversing lamp failure, and found corrosion). The lamps are not "smart lamps" in any way, and the lamp sensing circuit simply senses current draw. (Anecdotical: my auto DRL circuit turns on the fog lamps only, resulting in a lamp-out indication, likely because the rear lamps in the factory fog circuit are not drawing current at the same time). If you go the LED way, you will need a (integrated) resistor that matches the lamp, to get current up to the necessary level.

LED¨s are good, cause they hold "forever", but given the design of the monitoring circuit, current draw may not be much less.
 

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Super Moderator UK 2002 SLK320 Blue
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I had my driver's side rear light and brake light both give trouble recently. I took both my rear light clusters off and stripped each down then cleaned contacts with a fibreglass pencil and contact cleaner. No issues since. Took less than 30 minutes.

Also took opportunity to clean all the accumulated gunk from the bodywork and clusters too. Now the lights work AND the car is cleaner.
 

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Premium Member 2001 SLK320/2000 SLK230
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Discussion Starter #18
Agree, R170 is quite easy to work on. In my case it was clean so a quick wipe took care of dust and a bit of contact stretching was all it needed. Different taillight location L vs R had me going for a bit.

Now have a pair of spare 21W clears coming in and 21W amber single contact I had to swap for the OEM dual in the projectors is a good spare for the turn signals.

ps FMVSS requires amber front and red or amber rear turn signals so clear is right out in the US.
 

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Registered 2002 SLK 32
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42 Posts
Used the search feature and found this thread, it appears I might need some assistance to search for the correct fix, my running light does not work on the passenger side and attached a image to show that the connections are good. So any help to figure out why the bulb does not work would be appreciated. I realize it is the picture of the back of the light, but each bulb socket is fresh and show no signs of corrosion. So I am wondering where to start? Wiring diagram? Check ground? The brake light and turn signal work fine only running light on bottom outside. Also, if someone can inform me what the two small bulbs that are closest to the trunk do that would be great as these do not work either.
 

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