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Super Moderator UK 2002 SLK320 Blue
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Discussion Starter #1
Before I start this DIY I had to replace a blown lamp in the boot / trunk. This is done simply by easing the lamp housing out from the rear and unplugging the two wires connected to the housing. I then removed the old 44mm festoon lamp fitted to the housing and replaced it with an LED equivalent. Note that the metal contacts in the housing will benefit from a quick rub with a fibreglass pencil to remove any oxidation that may have accumulated.

Reconnect the cables and make sure the lamp lights up before fitting the housing back in the rear boot cover. If the LED lamp doesn't light up, take it out and swap ends and re-insert it. It should light up the other way round.

For the record, I fitted a cheap, non-CANBUS LED lamp. This may become important later on.

P2260114.jpg

Now we turn to the dome light in the car. You may have seen references to a Pelican Parts technical article about replacing the Dome Light lamp. In the article PelicanParts shows the removal of the dome light housing for a pre-facelift car. This DIY is therefore for a facelift (post-2000) vehicle as the dome lights are completely different.

Tools needed:
- plastic panel tool
- pozidrive screwdriver
- fibreglass pencil (like this one from Amazon)

Parts needed
- W5W LED lamps (I chose OSRAM Premium Retrofit W5W interior lights from Amazon)

The lamps do not need to be CANBUS compatible in this instance. They do, however, need to focus their light 'downwards' into the car and not 'sideways' as the light from the lamp will need to aim down into the car. The Osram ones I chose were called 'warm white' but are in fact 4000K so they are more of a 'cool white' and are a lot whiter than the old lamps which are around 2700K. They look like this:

Osram W5W LED_.jpg

Steps needed

Step 1 - Using a thumb or a plastic panel tool ease down the cover off the dome light.

P2260120.jpg
P2260121.jpg

Step 2 - Once the cover is safely off undo the two screws nearest to the windscreen. Be careful of the lens in front of the dome lamp. These are fragile and may break easily. They do not need to be touched to replace the lamps.

P2260122.jpg

Step 3 - Using the rear view mirror as a help ease the dome light housing towards the rear of the car and pull the front part of the housing down till the clips are visible.

P2260127.jpg

Step 4 - Now push the housing towards the front of the car and pull the rear part of the housing down till the metal clips release and the housing is free.

P2260128.jpg

Step 5 - You can see that there are two plugs and cables that are connected to the housing. The larger one on the end connects the lamps and switches. The smaller one in the centre is for the infrared sensor. Remove both plugs so the housing is free and can be attended to. You may have to unclip the smaller plug to separate it. If so, ease back the two grey clips and ease the connector out then pull the connectors apart.

P2260129.jpg

Step 6 - Turn the housing over and remove the old lamps by twisting the yellow holder anti-clockwise and pulling back towards you. You can see by looking at the metal track where the corrosion can creep in.

P2260131.jpg

Step 7 - Use a fibreglass pencil to clear away any oxide products that may be there and ensure a clean connection for the new LED lamp. Remove the old lamp by pulling the glass lamp and holder apart. Then clean the housing and the lamp holder.

P2260132.jpg


(As I've reached the max file limit I'll continue in Post 2 below)​
 

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Super Moderator UK 2002 SLK320 Blue
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Discussion Starter #2 (Edited)
Step 8 - Insert the new LED lamp by pushing the lamp fully home into the holder. Then put the lamp through the hole and turn the holder clockwise to secure it.

P2260134.jpg
P2260137.jpg

Step 9 - This is a picture of the housing with both lamps replaced and ready to re-assemble.

P2260145.jpg

Step 10 - Ease the cables down from the roof lining and plug them into place on the housing. The plugs are keyed so you can only plug them together one way.

P2260142.jpg

Step 11 - Offer the housing back up to roof and insert it as shown - cable-first. The housing will just click back into place ready for use. Insert and tighten the two screws (remember the housing is plastic - don't over-tighten them) then offer up and clip into place the outer cover of the housing.

P2260146.jpg
P2260147.jpg

Step 12 - That's it! Job done! Now turn the lamps on and bask in the new light in your car!

P2260148.jpg

I did try to show the difference between the two types of lamp - the new LED one and the older tungsten lamp. You can see that the older lamp (on the right) is yellower than the new LED type and less bright.

P2260136.jpg

As you can see in the picture above I also added a dashcam to the wiring in the dome light at the same time I added the LED lamps, but I'll write this up in a separate thread to keep things simple to follow.

Thanks for reading!
 

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Registered 2001 SLK230
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180 Posts
Thanks

Thanks. I just replaced the glove box light in my 2001 R170, and had been considering doing the same with the dome light. Though not difficult, it looks a lot more complicated than I had expected.

You did a really great writeup; thanks!

By the way, do your new LED bulbs dim like the old ones did? My dome light dims before it shuts off, a feature that I find annoying at times when I simply want to be sure it's definitely off before I go into the house.
 

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Super Moderator UK 2002 SLK320 Blue
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Discussion Starter #4
They do dim, yes. Apparently there is one issue in that there is an occasional flash from the dome light when the windows are moved up or down. I've not had a chance to verify this though as the weather has been so bad I've not been out in the car.

The dome lights aren't difficult - I've maybe over-done the steps but I know most people like to see step-by-step instructions for these as they go through the work on a computer before they tackle the job. If it takes you 15mins to change both lamps I'll be very surprised. The Osram lights I chose are plenty bright enough and are available from Amazon (link in first post above)
 

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Premium Member
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342 Posts
They do dim, yes. Apparently there is one issue in that there is an occasional flash from the dome light when the windows are moved up or down. I've not had a chance to verify this though as the weather has been so bad I've not been out in the car.
Hi Sav, when i disconnected my boot light to remove all the boot trim, my dome light was on all the time, but dimmed. I guess they must be part of the same circuit, not sure if that might be why you get your flashing problem but worth being aware of. Took me ages to figure out why the dome light was staying on all the time (well, not ages, but a little bit of time ruling other things out!)

Cheers,

Dez
 

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Super Moderator UK 2002 SLK320 Blue
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Discussion Starter #6
Hi Sav, when i disconnected my boot light to remove all the boot trim, my dome light was on all the time, but dimmed. I guess they must be part of the same circuit, not sure if that might be why you get your flashing problem but worth being aware of. Took me ages to figure out why the dome light was staying on all the time (well, not ages, but a little bit of time ruling other things out!)

Cheers,

Dez
Hi Dez - I've got the dome light wiring attached. There you can see how the boot light and the dome lights interact. E18/1 is the boot lamp and E15/1 is the Dome Light. All I can think of is that with the boot open the lighting controller (N10-3) was detecting the open boot and trying to switch the boot lamp and the dome lamps on by taking the blue-brown cable to ground as, logically, the boot light and the dome lights are in parallel with each other:
Dome Wiring.jpg
 

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Have the same trunk light issue!

Before I start this DIY I had to replace a blown lamp in the boot / trunk. This is done simply by easing the lamp housing out from the rear and unplugging the two wires connected to the housing. I then removed the old 44mm festoon lamp fitted to the housing and replaced it with an LED equivalent. Note that the metal contacts in the housing will benefit from a quick rub with a fibreglass pencil to remove any oxidation that may have accumulated.

Reconnect the cables and make sure the lamp lights up before fitting the housing back in the rear boot cover. If the LED lamp doesn't light up, take it out and swap ends and re-insert it. It should light up the other way round.

For the record, I fitted a cheap, non-CANBUS LED lamp. This may become important later on.
I needed this in my life...THANK YOU!
 

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Registered 2001 SLK320
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50 Posts
I replaced the light in the trunk with an LED when the old one burned out, and replaced the dome light with an LED when I had a bad-connection problem there. Definitely brighter, bluish light, and haven't had any problems since.
 

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Hi, nice write up. I have an alternate view to how to remove the bulb. I found in my car the housing plastic had degraded and was no longer holding the yellow bulb holders effectively. If you try to twist them off you can end up breaking them so be careful. I find it easier and less risky to remove the bulb diffuser shields.

Just use a needle nose plier and gently pull the middle bridge section (its the section I point to with my screw driver in the attached photo) Before you pull disengage the spring loaded clip on the left.

Once the shield is removed just simply pull out the bulb without twisting.
 

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Super Moderator UK 2002 SLK320 Blue
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2,933 Posts
Discussion Starter #10
I do have one further little tip to add to my write-up

I noticed after a while that one of the LEDs was flickering. By swapping left for right I found that it was the holder that was faulty - not the LED so I set about with a little repair.

If you look at the picture attached you can see that the metal contacts for the LED lamp sit around the hole that the lamp mounts in. I found some thin rigid plastic (the plastic from a takeaway container is about right) and I cut a sliver and inserted it between the contact and the plastic of the dome housing. After popping the LED back into place I've not had any further issues.

I would say that if you find the LED lamp is too difficult to insert after doing the mod then the plastic you've put in place is too thick. To give you an idea, the plastic from a credit card is too thick - you want something about a third of that thickness or less - and make sure it doesn't intrude into the space of the lamp.

Good luck!
 

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