Instrument cluster removal on a 108 - PeachParts Mercedes-Benz Forum

ievans · #1 01-20-2004, 05:17 PM

I'm having the damndest time getting the instrument cluster removed from my '73 280SE 4.5. I've searched the forum for instructions, and know that there's a plastic knurled nut that holds the cluster in, plus a press-fit rubber seal.

I've been fishing around the back of the dash feeling for the nut to no avail. It's possible that the nut wasn't reinstalled by the previous owner. OK, so the cluster should be able to be jiggered out. That doesn't work either. It feels like it's being held in, and I don't want to force it.

Where should the nut be located (specifically, if I'm looking at the cluster from the driver's seat, which part of the cluster is it behind)? I've felt a lot of stuff back there, but nothing like the plastic nuts used on the rear brake light enclosure.

Tomguy · #2 01-20-2004, 05:31 PM

It's directly in the middle, and located well behind the cluster - you must get it out by reaching from UNDER the dash (lie on your back on the driver's floorpan and look up. You should see it if it's there). Mine sits very tightly w/o it and needs "coaxing" (rocking back-and-forth) to remove it.

pyrOman · #3 01-20-2004, 06:06 PM

You may also be able to access it through the speaker cavity on top of the dashboard. If you don't have somewhat skinny hands get someone that does to help you here. I know how you feel, it is really tight in there!

I didn't re-installed the "thumb-nut" either. It looks like the same as those which hold the tailight assembly in the trunk.

Good luck!

ievans · #4 01-20-2004, 07:43 PM

No dice on the speaker hole. And no dice on the visual. With quite a bit of contorting I can see the back of the cluster, or at least a little bit of it (I think the speedo cable and two black plastic circles), but I don't see anyplace for the knurled nut.

It's not budging at all when I pull it out. I've been rocking it back and forth, but as soon as I let go it goes right back.

Boy, is this frustrating. All the directions make it seem to easy.

Tomguy · #5 01-20-2004, 10:44 PM

The speedo cable could still be holding it back - mine moves enough to pull the cluster, but yours may not (at least without a firm tug).

JoeyTheB · #6 01-20-2004, 11:56 PM

I'll bet the knob is still there - mine showed same symptoms the first time I took out.

Try this -
Drop the emergency brake handle
Disconnect the black electrical connector
Lay on back (as described above),
with your hand going up near the emer brake -
you should be able to wiggle around and feel the knob.

After you get the knob loose, you will be stopped by the speedo cable (as mentioned).

PS - Be Patient - goal is to NOT crack the dash !
(been there done that)

psfred · #7 01-21-2004, 01:50 PM

It's quite difficult to actually see the knob from underneath.

It's dead center both ways behind the cluster, hold the bridge across the back to the dash support.

You can only get to it from underneath. Drop the parking brake bracket and unplug the large wiring harness that runs across, and you should just be able to catch a glimpse of it. Mine was white, but if yours is black, you may not be able to see it.

You will have to stick your whole arm up there to find it, it's a long reach (elbow deep).Go in on the driver's side of the steering column.

If it is off, you will find the threaded rod sticking out of the bracket. While you are up there, unscrew the speedo cable. Expect to loose some skin, lots of sharp bits and NO room.

Watch out for the shift indicator cable, it gets in the way.

Peter

MikeTangas · #8 01-21-2004, 05:34 PM

Regarding the shift indicator that Peter mentioned. If you have a column shift and your indicator works, while you are under there getting at the knurled knob, carefully disconnect the end of the cable attached to the shift tube. It is a simple hook and loop end. Then carefully unthread the cable from the support hook a little higher up. Might be a good idea to have a flashlight with you, even if working in the daylight.

If you have a functional indicator you don't want to mess it up. These VDO indicators aren't cheap, probably $110 or more.

ievans · #9 01-21-2004, 07:01 PM

Well, my shift indicator isn't working. My working hypothesis is that the cable isn't attached any longer. Reattaching it is on the list of things to do with the cluster pulled (including replacing the dash bulbs, fixing the clock, and trying the odo fix).

I'll try feeling around for the nut again this evening. Thanks for the tips.

gerryvz · #10 01-22-2004, 05:28 AM

One thing that I've found helpful is to remove the parking-brake bracket and move it aside -- it gives more room for moving your arm around up there. Simple, apparent procedure.

DON'T replace the knurled nut, just keep it safe and handy.

Cheers,
Gerry

ievans · #11 01-23-2004, 04:36 AM

Thanks for the help, everyone. I found the nut and managed to get the cluster out. I'll try the speedo fix, get a whole mess o' bulbs, and take a look at the clock tomorrow.

psfred · #12 01-23-2004, 01:48 PM

Clock is an electrically wound mechanical clock -- if it doesn't run at all, chances are the internal fuse is blown --it's just a low temp solder joint holding a spring contact down. Re-solder with low temp solder from Radio Shack, NOT normal electrical solder, it won't blow.

It works by energizing a solenoid and flipping a weight up, the rotation of the weight back down to the contact drives the clock. YOu will hear it click once in a while if you sit with the engine off.

If it runs slow, the mechanicals need to be lubed. Use only very dilute instrument or sewing machine oil (one drop of oil in a mL or two of lighter fluid) and a shaved down matchstick to apply oil to the pivots of the mechanism ONLY. Keep the gears all clean and dry. Only use enough dilute oil to wet the pivots, you don't need any more. If it runs, you put too much on.

Old gummy oil is the usual slow running cause, just like any mechanical clock.

Peter

ievans · #13 01-23-2004, 04:23 PM

So, I have to crimp the bezel to get at the clock's internals, right? I took off the three screws on the back of the clock, but it looks like the bezel is holding the metal cover on.

How am I going to get the bezel off without ruining it?

pyrOman · #14 01-23-2004, 05:03 PM

I'm no expert but I've done many a clock already so this much I know.

The reason why the "fuse" blows in the first place is none other than wear of the mechanism thus slowing down to the point of jamming itself. When this happens at the point of "rewind" the heat of the constant electrical connection blows the fuse.

If you take the mechanism (or correct term: movement) apart and inspect it under a microscope, you'll see the small pin holes where the gears turn, have become slots instead of round holes. The slots now become so big that the gears either don't engage properly or just plain jam against each other. After 30 or 40 years of ticking these clocks will take a licking.

Though I'm not a watchmaker by trade, I stayed at a Holiday Inn last night! So I have "jewelled" a couple of these clocks so they will NOT wear out again.

Of course all that is relating the early windup type clocks. The "later" quartz ones are a different animal. If that's what you have and it doesn't work there's only 2 things that could go wrong, at least in my experience. Either the little motor in it is fried or one or more gears could be broken, mostly everything in there being plastic. When this babies are working they are just as accurate as anything telling time!

I did fix one with a running motor but with a broken gear. Simply took one with a fried motor apart and replaced the gear of the broken one with it. That was over 2 years ago and that mother is still ticking!