I Can See Paradise by the Dashboard Lights

[Mark in KS]

I knew the title would catch everyone's attention.  But my question is legitimate.  I replaced all the lights in the dashboard when I first purchased the car, but have always noticed that the tachometer lights brighter and more evenly than the speedometer.  Does anybody else have the same situation?  The tac is brighter.

I had the dash all apart last year and there were no bulbs burned out or pulled from their sockets.  I bought the bulb set from my good friend Ray Paul at SL Classics, so I know their all the same wattage, etc.

Any comments?

'67 230SL

[TR]

Yes, I've notice that same difference in brightness.  I know my bulbs are good and of the same wattage.  I don't know the source of this lighting discrepancy.  I'm glad you brought it up.  Hopefully someone will tell us.

Tom in Boise

[rmmchl]

I have the same problem. I noticed it when I had the glass on the sppedometer replaced and I replaced the bulb with a new one. I just ordered another new bulb from bud's benz. I don't ever remember the speedometer being that dull when I purchased the car in 1986. Does anyone have the answer? The tach is lit up well.

[hauser]

Same here.  Tach seems brighter than speedo.

1969 280sl 5 spd
Gainesville, Fl.

[Cees Klumper]

On my speedo and tach, the lighting is the same. I suggest you try a slightly different wattage on either to get them to be the same, if all else (positioning, cleanliness) checks out.

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[DaveB]

I think I remember reading about this somewhere. The tach is purposely brighter for the purist drivers who drive on revs alone. Gentlemen, start your engines.

DaveB

[Ben]

My RHD car is the same, tacho is brighter !

Glad I didn't try to fix it !

Regards,
Ben in Ireland.
'64 230SL 4sp.

[Jonny B]

To add one more vote, after I got my dash lights all in place last year, the tach was, and still is, a bit brighter.

Jonny B
1967 250SL Auto

[Mike Hughes]

The bulbs for both the tach and speedo are the same and are fitted to the rear back of the instruments in roughly similar locations.  What is different is what is inside the instrument cases.  The tach mechanicals are simply less bulky than those of the speedo.  The speedo mechanicals have the same indicator drive as the tach, but attached to this are the additional barrel drives for the odometer and trip odometer.  So there is simply more stuff inside the speedo to block the light getting around to the face of the instrument from the rear of the case.  Regardless of manufacturer, the innards of most instruments are roughly the same.  In particular the inside of the instrument case is almost universally sprayed white to improve light diffusion from the rear of the case to the face of the instrument.  This white paint can discolor, or even flake off over time.  I have had great success with improving the night time display quality of the Smiths and Jaeger instruments in my M.G.s and Jaguar by simply removing the works from the case and cleaning, preping and repainting the interior of the case with the "whitest" satin white spray paint I can find.  I can't imagine that the 113 instruments would not benefit from a similar procedure.  In addition, it is useful for longevity and accuracy to lubricate the two or three critical wear points of the indicator drive works with a drop of very light machine oil through a needle aplicator (I get mine from a watch repairman) while you have the works out of the case.

- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havanna Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

[Mark in KS]

Mike, a great reply.  I don't know why I didn't think of all the "extra" stuff in the speedometer when I was pondering it.

Thanks for the insight.....

[TR]

Gents -- My dash is totally apart right now, so the timing for this is perfect.  I had one of the mechanics bring over the speedo & tach so I could look at them.  Mike, the speedo sure does have more "stuff" to block those little lights, plus the bulbs appear to be mounted a tiny bit further back.  However, both instrument cases have lovely white rubber inserts completely lining the cases.  While apart those will be cleaned.

I see no way to even out the illumination between the speedo and tach without adjust one or the other.  So, what we plan to try is to insert a miniture potentiometer on the brighter of the two, meaning the tach, and then dim it down until it matches the speedo.

That little pot. will not be visible after the small adjustment is made.

Tom in Boise