Author Topic: Tach noise (Read 15911 times)

jimj · « **on:** January 04, 2006, 08:23:34 »

Guys, been lurking here for a few months, but now I have a question/problem with my 1968 280SL. Went out this weekend and fired the car up after it had been sitting for a couple of months, and danged if it didn't sound like I had stepped on the cat's tail. There was a gosh-awful squealling coming from the tach that varied with the rpm's of the engine. If I was a little more talented, I could have played a tune on that sucker.

After pecking on the tach face a couple of times the squeal went away but, when I left the garage on a short trip to warm up the transmission and rearend, the squeal resumed and now I can't get rid of it.

The noise is definitely coming from the tach and I haven't been able to get my hand up behind the cluster to disconnect the drive cable in an attempt to isolate the problem to the gauge or cable
Btw, the tach is still reading normally.

Any ideas/suggestions before the neighbors have me locked up for pet abuse?

waltklatt · « **Reply #1 on:** January 04, 2006, 08:39:46 »

Jim,
The cable sounds like it's out of lubrication grease. You will need to stick your hand up into the cavity behind the tach and unscrew the knurled nut holding the bracket for the tachometer. Push the tach out from the dash and then unscrew the tach cable. Squirt a few drops of 80 weight oil into the orifice and then smear a bit of grease into the opening. Then turn on the motor to observe the rotation of the cable inside. If it still squeals then it's a replacement time.
Walter Klatt
1967 220SL-diesel
1963 230SL-gas

Jonny B · « **Reply #2 on:** January 04, 2006, 11:19:12 »

This is almost a contortionists job to get to, but still reasonable. It helps to have small hands. Remember to check for the grounding cable on the knurled nut (that holds the tachometer bracket, or keeper in place) and to put it back when you are done. Also, this is a good time to check the bulbs, at least the ones in the tach.

Jonny B
1967 250SL Auto

J. Huber · « **Reply #3 on:** January 04, 2006, 11:32:52 »

Jim, I'll be the one to add the slightly more involved problem "potentially": sometimes, even replacing the cable will not cure your problem. What will is removing the tach and having it rebuilt by specialists. Many of us here have had to do it -- so I'd say its fairly common. Two reputable outfits that do it are Palo Alto Speedometer and I believe its called Hollywood Speedometer. There might be others. A rebuild might run you 125 to 150. Mine was 125. Perhaps others will share their experience on this approach. Good luck!

James
63 230SL

114015 · « **Reply #4 on:** January 04, 2006, 15:27:01 »

Hello Jim,

Yes, I agree fully to what the colleagues already said. Try to lubricate the tach cable first. If the noise persists, a tach overhaul is in time.
The both names (just google for the addresses) for the shops are first choice.

Good luck!

Achim
(Magdeburg, Germany)

114015 · « **Reply #5 on:** January 04, 2006, 15:30:05 »

I used North Hollywood Speedometer for a total of 10 instruments (including clocks). They all came out like new. However, I had so far only the chance to check the speedo of my sedan, which was overhauled as well. The result is fine.
Price is about what James already mentioned.

Best,

Achim
(Magdeburg, Germany)

TR · « **Reply #6 on:** January 04, 2006, 21:55:10 »

David Pease, are you reading this thread?

Sounds familiar, eh? Thank you again, David, for kindly disconnecting the tach connection at the front of my engine. You saved my bacon then (while we were all together at Dick & Ann's beautiful place in Nevada City) and on the long drive up the California and Oregon coasts and then back to Boise. As JimJ accurately points out about this problem, the noise is really obnoxious.

BTW, we drank a bottle of the Ferrari-Carano late-harvest muscat (with chocolate blueberries, of course!) as an after-dinner treat at Thanksgiving. Your recommendation on that was an excellent one.

Tom in Boise
'71 280SL 4-spd, signal red w/lt. tan interior, restored/enhanced

LFrank · « **Reply #7 on:** January 05, 2006, 10:54:43 »

My $.02: have the same squealing tachometer, but only when temp dips to around freezing...never a problem in warmer weather.

LFrank
Washington DC
65 230 sl - auto
DB334/Hellblau

Cees Klumper · « **Reply #8 on:** January 06, 2006, 15:48:11 »

My 'squeeling tach' problem exhibited itself about 5 years ago, mostly in cold weather. Unlike other posters, I cured the issue simply by replacing the tach cable, no rebuild. That did the trick and the problem never came back. While I had the tach out, I also cleaned the inside of the glass.

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

DavidAPease · « **Reply #9 on:** January 09, 2006, 00:58:55 »

Hi, Tom!

Happy New Year to you and everyone; I'm just catching up on the Forum after the holidays.

I'm glad that both suggestions (disconnecting the tach cable for the remainder of the trip, and the Muscat) were a success. I'm looking forward another wine-tasting trip together sometime.

-David Pease
'66 French 230SL

Dick M · « **Reply #10 on:** January 09, 2006, 02:28:00 »

David and Tom...
Next spring in Oregon.. Pinot
My screeming tack in cold weather turned out to be the instrument... Jumping speedometer was cable.. I had gages refurbished in Sacramento ($85) and put in new speedo cable... now life is wonderful.

jimj · « **Reply #11 on:** January 26, 2006, 08:21:20 »

Well, I'm not a contortionist, nor do I have really small hands, but this past weekend, I did teach the dog some new curse words and managed to get the old tach out of the car. Turns out that my squeal is coming from the instrument itself, and it and the clock are on their way to North Hollywood Instruments for some freshening up.

But, as is always the case,while doing this, I also determined why the lighting for my tach doesn't work. Seems that one of the tiny screws that hold the leads to the post on the back of the tach has gone AWOL, so I need to come up with another.

Does anyone know what size this tiny screw is? I'm sure I can find one in town, but just need to know what to ask for.

waltklatt · « **Reply #12 on:** January 26, 2006, 08:35:01 »

Jim,
That wire(brown) you are referring to has a metal clamp with a hole in it? If that is the one, then that goes onto the long threaded bolt sticking out the back of the tach. After the bracket is put on then the wire and then the knurled nut.
Walter Klatt
1967 220SL-diesel
1963 230SL-gas

jimj · « **Reply #13 on:** January 26, 2006, 11:33:22 »

Walt, it's not the ground wire that attaches with the knurled nut retaining the tach, it's the tiny screw that connects the electrical leads to the lights for the tach. The lead from the harness has a soldered tip that inserts into a hole in the post, and the tiny screw then screws into the end of the post to retain the wire.

Benz Dr. · « **Reply #14 on:** January 26, 2006, 12:55:58 »

This is a common problem and can be found in both the tach and the speedo - even on sedans. These things work on a mechanical system that uses a magnet spinning inside of a drum. The grease around the shaft gets hard or dries up and is much worse in cold weather. In most cases it goes away after the interior of the car warms up or in the summer heat. It's possible to remove the guage and repair this yourself but a good cleaning and calibration might be in order anyway.

Dan Caron's
SL Barn
benzbarn@ebtech.net
slbarn.mbz.org
1 877 661 6061

waltklatt · « **Reply #15 on:** January 26, 2006, 13:12:11 »

Ahh Jim, that's the light bulb power wire you are referring to. Key word was soldered tip. That should go into the center shaft of the light bulb holder that slips into the two holes in the back of the tach. Do you still have the bulb and holder? If not then I can send you a spare of mine.
Walter Klatt
1967 220SL-diesel
1963 230SL-gas

jimj · « **Reply #16 on:** January 26, 2006, 14:03:50 »

I have the bulbs and all, just need the little screw that retains the power wire, and only one 1 them at that. The other one was tight.

waltklatt · « **Reply #17 on:** January 26, 2006, 14:41:02 »

Quick, what's your address?
I'll tape 2 screws inside an envelope for you and mail it tomorrow.
Walter Klatt
1967 220SL-diesel
1963 230SL-gas

waltklatt · « **Reply #18 on:** January 27, 2006, 13:33:02 »

Jim,
Got it and they will be in tomorrows mail.
Best to edit out your address so other's wont flood to your home for pieces of your SL.

Walter Klatt
1967 220SL-diesel
1963 230SL-gas

jimj · « **Reply #19 on:** January 31, 2006, 06:47:27 »

Walt, I got the screws yesterday, and I would like to express my appreciation for your gracious gesture. If you ever find yourself in Lexington, KY, look me up and I'll buy you a drink of your favorite potion.

jeffc280sl · « **Reply #20 on:** March 10, 2008, 20:48:31 »

Just found the noise culprit on my tach. Like most I had a squeal when very cold which got better as the car ran and went away as warmer weather arrived. This past weekend it started howling full time. Took the cable out. Cleaned it and lubed it with graphite. No change. While I had the tach out I hooked it up to the cable and played with strain relief etc trying to change the squealing. There was a slight change in pitch as I moved the cable around but this was not the solution. I decided to put a couple of drops of oil on the tach bushing that the square tach cable plugs into. Noise disappeared immediately. The shaft that takes the square inner drive cable spins with the engine revs. It has a bronze bushing around it that is stationary and fixed to the bracket where you screw the tach cable end. The inner shaft need to spin freely in the bushing. If it doesn't you will get noise and a jittery reading. Just though to post the findings from my car and hope others will try this fix and report back there findings.

Maybe those that solved the problem with a new cable really had a bad cable that was transmitting noise through the tach. Or, maybe some oil on the new cable found its way to this bushing and that helped quiet things down.

Jeff C.
1970 280SL 4-speed

PnHi · « **Reply #21 on:** May 02, 2008, 15:26:35 »

quote:
Originally posted by jeffc280sl

Just found the noise culprit on my tach. Like most I had a squeal when very cold which got better as the car ran and went away as warmer weather arrived. This past weekend it started howling full time. Took the cable out. Cleaned it and lubed it with graphite. No change. While I had the tach out I hooked it up to the cable and played with strain relief etc trying to change the squealing. There was a slight change in pitch as I moved the cable around but this was not the solution. I decided to put a couple of drops of oil on the tach bushing that the square tach cable plugs into. Noise disappeared immediately. The shaft that takes the square inner drive cable spins with the engine revs. It has a bronze bushing around it that is stationary and fixed to the bracket where you screw the tach cable end. The inner shaft need to spin freely in the bushing. If it doesn't you will get noise and a jittery reading. Just though to post the findings from my car and hope others will try this fix and report back there findings.

Maybe those that solved the problem with a new cable really had a bad cable that was transmitting noise through the tach. Or, maybe some oil on the new cable found its way to this bushing and that helped quiet things down.

Jeff C.
1970 280SL 4-speed

Jeff
Again thank you for sharing with the group. I was about to send my tach out for another rebuild (or whatever) after only 6k miles and decided to try a few drops of oil in the bushing and hooked it up to the cable just sitting in the dash. After a hundred miles no squeal. Reinstalling tonight.

Mike C
68 250SL

James Stern · « **Reply #22 on:** May 05, 2008, 12:24:32 »

can someone tell me where the exact steps for tach removal are listed.

Thanks,

Jim

James Stern · « **Reply #23 on:** May 05, 2008, 13:56:25 »

Nevermind. I found the thread elsewhere in the Forums.

Thanks Anyway,

Jim

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Author Topic: Tach noise (Read 15911 times)

jimj

TR

LFrank

Dick M

jimj

jimj

jimj

jimj

jeffc280sl

PnHi

James Stern

James Stern