6W Instrument Bulbs Installed! Let There Be Light!

[Rolf-Dieter ✝︎]

My odometer light bulb in my 280 SL 1969 is burned out. Has anyone changed it?

Is it a big deal? What bulb size do I need?

Thanks for your help fellows

[66andBlue]

Since the odometer does not have its own bulb I assume you mean the speedometer, correct?
Take a look here: http://www.sl113.org/wiki/Electrical/Speedo
In the photos you can see two round sockets (one goes through the bracket) for the bulb holders and info on the bulb.
Not a big deal, but a PITA - because to get access to the bulb holders you need to remove the tachometer and reach behind and around the center cluster instruments. Easiest to remove all three instruments. See also photos here: http://www.sl113.org/wiki/Electrical/RevCounter

[pj]

The tech manual says OSRAM # 3796, so I found this document:
www.osram.com.hk/osram_hk/EN/Local_Activities/English_Catalog/OSRAM_Automotive_lamps_2009_2010.pdf
and if you go immediately to page 27, you will find 3796 listed there. But what interests me is that # 3894, just 3 lines down, has the same voltage, same socket, same bulb dimensions . . . but it's a 3W bulb, not 2W.
What do you think? Would it work to brighten up the speedo and tacho a bit if we used a modern 3894 when replacing the bulbs in our instruments? I presume it would draw 250 milliAmps from the electrical system instead of 167 mA, but would that be a problem?

OSRAM's a big company with at least some incentive to care about their heritage, so more ideas might be out there somewhere.

[ABikePeddler]

Well, I just went for it. Tired of barely being able to read my instruments at night I made it my Labor Day project to replace all the 2W instrument bulbs with 6W replacements and WOW, what a difference!  While the orangeish glow of the dim bulbs is somehow more "classic "Benz", being able to now see (and control) the dash lighting is VASTLY more practical.  Here, look for yourselves...

The before photo is actually just with the new bulbs turned down to approximately their old maximum dim setting using the rheostat.  The brighter images are at full brightness.  In reality they are not quite as bright as it appears on camera but they are vibrant, fresh and look "new".  I just love it.  Hoping the jump up from 2W to 6W won't lead to any issues.  We'll see.

 

[pj]

Hello Eric,
great idea! I think your first picture answers one of my long-standing questions because the upper half of my centre instruments is dark. I figure there are 2 bulbs in there and one of mine is kaput.
So how many bulbs did you need, and where did you buy the 6W bulbs?
But most important: how did you do it? Part of a bigger project to remove the dash? Or what?

[Cees Klumper]

As far as I know I have original 2W bulbs and I can see the instruments just fine. That is with the rheostat bypassed, so full strength. The only issue I would worry about with going to the 6w is the additional heat they might give off, and whether the wiring won't overheat (we don't want that!), but that may be a lesser risk.

[ABikePeddler]

Heat. That is my concern also... additional heat as well as the additional draw on the cars 48 year old wiring. But I ran these new 6W bulbs in the tachometer since April with no ill effects.  (I didn't finish installing the remaining bulbs until just this weekend.)  Below is a picture from April showing the new bulbs in the tach while the old bulbs remained in the rest of the instruments....

I purchased the bulbs from Candlepower.com here: http://store.candlepower.com/38xefiinpala.html   You will need 5 bulbs total to replace the existing bulbs in the 3 main gauges.  I purchased extras in case I had any D.O.A bulbs from the retailer.

Note: As with even the standard bulbs, the speedometer is slightly less well lit then the tachometer.  That is by design.  It's just the way the bulbs are situated behind the gauge face that causes this uneven lighting.  Not much can be done about it. 

As to the question about the center gauge having two bulbs, mine only had one which is located direct center in the rectangular gauge cluster. Because the bulb is located in between the 4 small gauges I decided the best way to access it was the pull out the oil pressure gauge (which is held on with two small screws on the back side of the gauge) so I could gain access to the bulb.  It is a tight fit trying to remove that bulb with bare fingers but it worked fine and the new bulb slotted in with ease. The center gauge does have other bulbs (turn signal, low fuel light etc...) but they are not related to the main objective of overall gauge lighting. Once installed, I recommend carefully wiping down the bulb glass if you have to handle them with bare fingers.  Right or wrong, I have always heard that the oils from ones skin can cause a shorter life for the bulbs.

There are numerous excellent write-ups on this forum about how to remove the gauges so do some searching.  Most all of them comment on how difficult it is to remove the gauges from the dash. I did not find this to be true at all. Sure, it is a tight fit reaching up behind the dash to first undo the tachometer but from there, it really isn't a big deal.  Whole project was done in less then 2 hours and that was including removing the chrome bezels so I could clean the glass and inside of gauges. 

Next:  Remove the HIVAC (Heating Ventilation Controls) controls and install new bulbs in there.  My controls work fine but the current, original 2w bulbs barely qualify as lighting and the Lucite controls themselves are so filthy they are not illuminating as they should. Will try and post pics of that project when I can.

[66andBlue]

Bike Peddler,
for how long did you run the bulbs continuously at full power, 10 minutes, 1 hour, 5 hours?
I would be worried about putting 12 watt heat into small space like a speedometer -  my circuit board soldering iron produces 12W !!
Like you i wanted brighter lights but decided to exchange them for 4-LED bulbs since they stay cool:
https://www.superbrightleds.com/moreinfo/ba9s-ba7s/ba9s-led-bulb-4-led/6/
The photo shows the effect of the rheostat.
I'll put more info on LED changes into the technical manual soon.
 

[Rolf-Dieter ✝︎]

I like to add my 2 cents here ... In real life Engineers and Designers use components that are safe and right for the application. That also applies to our cars. If you change things you take the risk of asking for trouble. I have to change a bulb in my speedometer, however, the bulb that came out will be replaced with a new one of the same make and wattage.

Be safe fellows ... don't take risks replacing wiring can be a major project, if it turns into a fire you may as well kiss your Pagoda good bye.

Peter, changing bulbs on our cars is not the easiest task. I'll show you next time you come by my old odometer how to remove the mounting bracket, then the protective cover to gain access to the bulbs and finally using two finger tips pushing in the bayonet-type mounting bulb to remove it. All this after one removed the tach.

There is a write up in the Technical Manual as to how to remove the tach.

Link right here ---> http://www.sl113.org/wiki/Electrical/Speedo#Lights

[ABikePeddler]

66andBlue: I have been running the bulbs in the tachometer since late April.  I drive the car daily, much of the time with the lights on, so I'd estimate I have over 25 total hours run time on the 6W bulbs in the tachometer with no ill effects.  But I didn't expect there to be an issue with these bulbs until I installed the remaining 3 bulbs as the real draw on the system would only happen once all were installed.  I will update this post if there is ever an issue. 

Your LED lighting looks fantastic!  As with most LED's, the lighting is usually a little blue.  Is that the case with yours?  (Hard to tell from pictures) Also, LED's generally are not dimable... is that also the case with yours?  I like the idea of using LED's as there really isn't many drawbacks to them... low cost, low energy usage, low heat, and super long bulb life.  Negatives usually are unnatural color lighting and lack of dimability.   

[66andBlue]

Peddler,
I do not perceive them as "blueish" but cool white, certainly not warm as the incandescent, and yes they can be dimmed using the rheostat in our cars. See my photo, the upper photo shows the lights dimmed with the rheostat.
But not all bulbs in the center cluster instrument can accept LED.  More on this in the technical manual later.

Rolf-Dieter,
I agree that one should not "... take risks  replacing wiring can be a major project") but please notice there are no wiring changes.
The 4-LED bulb draws less than 30 milliAmps compared to 0.14 Amp for a 2 W bulb (at 14V)  or 3x more for the 6 W bulb. So they are safer and more economical and I bet the MB engineers would have used them too 50 years ago.

[garymand]

I've wondered why the lights are so dim with with the pot full on.  2w is not much light from these filiment bulbs.  Maybe the Germans thought it would be best for night vision to use very low wattage AND further reduce the intensity through the pot.  To put some fears aside: 1) oil on the bulbs has no effect on filliment life, it is outside the glass.  The filliments are in a vacuum and unaffected by paint or oil to any measurable effect on the outside. (the bulbs that have that warning are very high intensity projection bulbs and I'm not sure I understand the problem issue other than the glass cracking. 2) apparently the pot never gives full current to the bulbs as Cees says they burn brighter with it bypassed.  So they aren't getting the full 5-6 W.  Thanks Cees, I've wondered about why the bulbs never go to full bright white light.  4) Heat?  well the wiring is more than ample for the current, the wires won't heat up, but the heat from the bulbs might be a problem if they are surounded by plastic that may be heat sensitive.  5) You can turn the brightness down to some comfortable level. 6) I and I'm sure many of you have replaced dash lights in other cars, 5W is about normal for what I see in other cars.

But ,,,I really like the led version especially if we can dim them.  This isn't something I would do on a whim, but I need to replace my ignition switch and speedo cable anyway.

BTW, Nice result pictures, thanks.

[66andBlue]

...  To put some fears aside: 1) oil on the bulbs has no effect on filliment life, it is outside the glass.  The filliments are in a vacuum and unaffected by paint or oil to any measurable effect on the outside. (the bulbs that have that warning are very high intensity projection bulbs and I'm not sure I understand the problem issue other than the glass cracking.

See: http://en.wikipedia.org/wiki/Halogen_lamp
Any surface contamination, notably the oil from human fingertips, can damage the quartz envelope when it is heated. Contaminants will create a hot spot on the bulb surface when the lamp is turned on. This extreme, localized heat causes the quartz to change from its vitreous form into a weaker, crystalline form that leaks gas. This weakening may also cause the bulb to form a bubble, weakening it and leading to its explosion.[18] Consequently, manufacturers recommend that quartz lamps should be handled without touching the clear quartz, either by using a clean paper towel or carefully holding the porcelain base. If the quartz is contaminated in any way, it must be thoroughly cleaned with alcohol and dried before use.

 

2) apparently the pot never gives full current to the bulbs as Cees says they burn brighter with it bypassed.  So they aren't getting the full 5-6 W.  Thanks Cees, I've wondered about why the bulbs never go to full bright white light.  

I don't think Cees wrote what you think he did.  
In any case it is not correct. A well functioning rheostat will change the resistance from 0 Ohm to to 18 Ohm and there should be no drop in voltage caused by the rheostat. If it does then it needs to be cleaned!
See: http://www.sl113.org/wiki/Electrical/Rheostat
Incandescent light bulbs do turn dark slowly with age and thus become less bright. No need to blame this on the rheostat.  

[ghenne]

Surface contamination is indeed a problem with halogen bulbs, because of the heat they output. However, are these bulbs halogens?

[Sableco]

Hello 66andBlue
I would agree that the Led lights are a better choice for the advantages mentioned by all.
the vendor offers them in 32 or 90 degree light bulbs, which ones did you use?
Thanks a lot for all the info.

Basem

[pj]

Hi Alfred,
those LED bulbs from the superbright website look very interesting and quite reasonably priced. Did you buy the "Cool White" colour? Any thoughts on what the other colours would look like in our instruments?

[garymand]

Ahh yes, Halogen and vitrious quartz envelopes, bubbles form and the envelopes explode.  I understand exactly what that says.  I'm glad I can still handle ordinary light bulbs with my bare hands.  I'd hate to have the bulbs in my house, or dash board, blowing up around me. 

[garymand]

Take a look at this parallel topic,  basically no problem with 3W some are using 6W and not mentioning and blown fuses.  If you count all the bulbs on the circuit and multiply by .25Amp (250mA), the answer should be 1/2 the fuse Amp rating.  If there are 8 bulbs X .25 = 2 Amp.  With 8, 6W bulbs its still just 4 Amps.  Or you might want to go to LEDs as covered in the topic. 

[Rolf-Dieter ✝︎]

Thanks Alfred, Yes I did mean the Speedometer. I explored the issue a few days ago by disassembling the old one I got with the car having the original milage. I also found the write up in the Technical Manual. I will (once I get a set of replacement bulbs) remove the speedometer and change out the bulbs. There is no urgency since I don't intend to do much night driving perhaps on my way home from Williamsburg, VA I may put in some evening driving.

Meanwhile I'm following the thread of "6W Instrument Bulbs Installed! Let There Be Light!" Perhaps I will change them all out to a bit stronger Wattage.

[49er]

Sorry guys but I still like the old timey look of the original "dim" bulbs. Maybe when and if the day comes when I need to replace them,  I might change my mind.

John

[garymand]

We get used to them, don't we.  I really do think they are dim on purpose for better night vision.

[66andBlue]

John and garymand,
I agree with both of you. I also prefer to have dim lights at night time (in any car I drive) and for this reason I would never bypass the rheostat. It is during twilight that I want brighter lights and the LED are almost perfect for this.
When you took this photo, John, were the lights at full brightness?

[66andBlue]

Hi Alfred,
those LED bulbs from the superbright website look very interesting and quite reasonably priced. Did you buy the "Cool White" colour? Any thoughts on what the other colours would look like in our instruments?

Peter,
unfortunately at this time the Ba9s 4-LED bulbs are only available in "cool white" (plus blue, green, yellow and red) but my guess is that in the near future there will be "warm white" available also. The company already sells a Festoon bulb in "warm white".

...the vendor offers them in 32 or 90 degree light bulbs, which ones did you use?

Basem
for the tachometer and speedometer and also for the center instrument panel I used 90 degree 4-LED.
All the other bulbs in this cluster are 1-LED and also 90 degree. 
Note that not all bulbs can be replaced with LED!
The red indicator light for battery charging (which is also the warning light for "door open" and "low brake fluid") must have some resistance otherwise the charging circuit is compromised!
The opening for "low fuel level" warning light in the housing (on the left in the photo) is too narrow to accept a 1-LED.

[garymand]

Nice pic, I better get my order in before they run out of stock.

[garymand]

Does the stock flasher work with the LEDs or do we also need the LED compatible electronic flasher?

[pj]

Hello Alfred,
that photo of the "inside" of the central instrument cluster is extremely helpful! Especially because I've never seen one opened up. But still there are questions. . . For one thing, you've labelled the red LED as blue. 1 point for me if I figured this out, 1 point for you if it really is supposed to be blue 

Are the green LEDs used for turn signal indicators bright enough to be seen in daylight? I find my stock turn signal indicators are almost invisible in daylight.

Did you hang on to the part numbers if you ordered these LEDs from www.superbrightleds.com ? Why not make a list? If you didn't, I'll scour their website and see if I can figure which one is which.

The low-fuel lamp is just a regular 2W bulb? So the red colour comes from a lens in front of the lamp? This one I probably would not want to make brighter.

[66andBlue]

Hi Peter, 1:nil for you!
I colored the borders and arrow red but mistyped the text, it should read "red", not 'blue".
--Corrected April 6, 2017!
The turn signal indicators are really bright, especially when it is dark, and I am not sure whether I should replace them with the 1-LED bulbs.
I do have a list of all the part numbers - including LEDs for other locations that I plan to put into the technical manual. I replaced the Festoon bulbs in the glove box, license plate illumination, and shifter console (for automatic 280SLs) also. Can you believe that they all have different lengths?!
And yes, the fuel warning light is a regular 2W, there is a red filter inside the housing.

[awolff280sl]

Great work Alfred!
Regarding accessing the bulbs in the center cluster, and referring to your picture ( and using the pictures at http://www.sl113.org/wiki/pmwiki.php?n=Electrical.Temperature ), how is the frame/glass part separated from the part holding the bulbs? I see that both the temp and oil gauges are removed first.

[66andBlue]

Hi Andy,
you need to unscrew the back as described here:


then you just lift the bulb holder together with the rheostat off. No need to remove the Bakelite cover or any other screws.

If your capillary to the temperature gauge is original, that is has not been repaired and shortened, thyen you should be able to pull the unit into the cabin far enough to remove individual parts from the cluster without unscrewing the temp sensor on the engine block.
Haven't had a chance to add all of this to the manual because of an upcoming trip to Europe.

[awolff280sl]

Thanks Alfred

[ricky9089]

how do you remove the dimmer knob from the shaft

[awolff280sl]

the dimmer knob is not removed from the shaft, rather the shaft is pulled back out of the knob. You do this by removing the back of the center cluster as described above. The knob remains on the glass. When you reassemble, be sure that the shaft lines back up with the knob. The glass could break if it is not when the back of the cluster is screwed back down.

[bsimaz]

I'm in the middle of replacing bulbs and re-installing the instruments.

a few notes:  I am planning going the LED route.  They are OK for some but not all the light bulbs.   There is one socket on my revolution counter that will not accept the LED bulb.   The LED's are too big to fit.  This is also true for the light behind the instrument panel.  The rest will fit and they do look great.

I've read all about the removal and re-install of the dash but I'll tell you this....  I'm about one more try away from paying someone Airfare, hotel, meals and expenses to come out here and do it for me.    I've been at it for two evenings now and I don't have one of them in.
It is a tight space.

Good news is that I have a long weekend ahead.

[awolff280sl]

Bill,
I can relate completely. But there is hope. It used to take me over 2 hours to do it, now I can do it in under an hour with minimal pain.
For me the trick was finding the correct route to the back of the tach with my right hand, and this happened when I changed my entire approach.
I used to lie on my back with my head on the pedals, very cumbersome.
Now, with the steering wheel and electrical connector bracket removed, I can partially sit on the seat, and reach my right hand under and around to disconnect the vent hose and then the tach bracket.
If you haven't tried this, I can recommend this.
I also had a problem with an LED being too big. I had to carefully take a Dremel to the socket.

[mdsalemi]

For me the trick was finding the correct route to the back of the tach with my right hand, and this happened when I changed my entire approach.

Don't forget friends, that Andy is a SURGEON.  He has skills the rest of us frankly do NOT have! 

[49er]

John, were the lights at full brightness?

Sorry Alfred, for some reason I missed seeing your question from a while back. Yes, they were cranked all the way on. The rheostat still functions OK but I just leave them set at full brightness.

John 

[mmizesko]

Alfred,

After Joe Alexander and I replaced all the bulbs in my dash after a rheostat hard wire last spring, I just bought a full set of LED's per your suggestion.  I added one 4 LED white bulb for the clock.  I too have a hard time reading the gauges at night, and need to have the dash apart anyway for a full body paint restoration next month.  I can't wait to see the light again!

Mike

[awolff280sl]

Mike, ortho surgery tends to be easier: good exposure, good assistants, good light, good retraction. You don't usually get any of that working on the Pagoda.

I also put in LEDs all around and I'm pretty happy with the results. However, both the tach and especially the speedo are not as bright as the center cluster.
I happened to look at the Bud's Benz apparent repros ($$$$) of the rubber covers for the back of the speedo and tach. I was struck by how white they are
compared to what I have. So, I've decided to have the inside of the rubber housings painted gloss white by Palo Alto Speedometer. I'm waiting to get them back now. Apparently, the vintage Porshe owners have had good results with this method, but their instrument housings are metal, so we'll see.

[66andBlue]

... I added one 4 LED white bulb for the clock.  ....

Hi Mike,
What kind of clock do you have?
I tried to get a 1-LED in there but had no success. Perhaps I need to take another look.

[mmizesko]

Alfred,

I've got the standard VDO.  I just ordered all of the LED's being inspired by your experience. I'll probably face the same problem when we try to get it in there.

Joe promises me he can fix my 5 minute per day loss problem.

I'll let you know how it goes.

Andy,

I'm an old collegiate shot putter with hands like hams.  Pre-med for 2 weeks.  With orthopedic surgery, I'm always the patient, not the practitioner.  Good thing Joe Alexander is there to help.  We've already had everything out once already last year, so I know the sequence.  I've got a howling tach when it gets cold, so I need to send it out for repair while the car is in the paint shop this winter.

[awolff280sl]

Alfred,
I was able to get an LED into the quartz VDO clock.

Mike, you are lucky that Joe is near. He's walked me through some rather dark and scary regions by remote control.

[mmizesko]

Alfred,

Just an fyi.  Had to pull out the dash components to get the wood out, as I'm replacing the windshield during my exterior paint restoration.  The clock light bulb will only fit a 1 LED bulb, and we had to grind down the bulb to the metal on the sides (on a wheel) to remove the plastic bulge and the metal flange.  Also had to remove about 1/8" off the top of the bulb, but still left enough room on the stalk to protect the LED component.  It did leave the plastic translucent instead of clear, but I hope it is kind of like a frosted bulb.

Put the clock back in and the instrument cluster and I like the brightness.  Sent the tach and speedo out for refurb so I don't know what they look like yet.

I don't think the grinding will compromise the LED or create a safety issue. But the bulbs are only $2 each.

Mike Mizesko
Columbus, OH

[IXLR8]

Hi--

In working with other electrical items, I have found that manufacturers will sometimes specify a lower wattage bulb specifically to keep the heat down in order to increase the life of the bulb.

Additionally, as was pointed out, the specifications of 50 some years ago probably were the best for the bulb life of that era.

Today, the leds better accomplish the same goal.

the other Joe

[Moe]

Hi, I am new to this forum and came across your reply stating that you plan to put the list of replacement bulbs (to LED) for the instrument panel.  I have a 1966 230SL and I am planning to replace all the bulbs - tach, speedo meter, and the center section light bulbs.  Any pointer to a list of bulbs/part numbers (LED) from www.superbrightleds.com or any other site would be much appreciated.

Thanks in advance.

Moe

[Jonny B]

Moe,

Try the search engine for this. There are quite a few topics on the LED light installation.

Use the main search function, the link to the right of "Home", between "Technical Manual" and "Admin" this will search the entire forum. The one at the top right, just under the club logo will only search in the forum you are reading.

I used "led light" with the quote marks, and got a single page of items. There are several dealing with dash lights, and there are some further links within each thread.

Good luck. And welcome to the group!