Author Topic: Tachometer 'Screech'  (Read 679 times)

jlimpic

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Tachometer 'Screech'
« on: January 16, 2021, 21:21:41 »
I have heard other members mention this issue and curious about the proper repair of the tachometer that screeches. Pulled the harness so it stopped.

Wondering if tach needs to be replaced or can be repaired? if repaired, looking for recommendation preferably in Southwest, or anywhere in US.

appreciate anyones thoughts and all replies.

Cheers

Pawel66

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Re: Tachometer 'Screech'
« Reply #1 on: January 16, 2021, 22:11:04 »
Screetching tacho often means it needs to be rebuilt. If it is vibrating while screetching - it just proves it.  Not sure what you mean by "pulled the harness so it stopped".

There are rebuild services in the US - the US Members will chime in to advise, or use the search function - it has been discussed many times.
Pawel

280SL 1970 automatic 180G Silver
W128 220SE
W121 190SL
G-class

jlimpic

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Re: Tachometer 'Screech'
« Reply #2 on: January 16, 2021, 22:33:10 »
Pawel66,

thank you for the reply

my mechanic detached the wiring to stop the screech.  He would not remove though as he said it tends to scratch the dash when removing.

cheers

Mike Hughes

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Re: Tachometer 'Screech'
« Reply #3 on: January 17, 2021, 00:57:41 »
Send your instruments off to Palo Alto Speedometer in California.  Many people on these forums, including me, have used them with very satisfactory results.  Send both your tach and speedo to be serviced and you won't have to worry about them again for a very long time. 

I say instruments (plural) because if your 50-odd year old tach needs attention, your 50-odd year old speedo won't be far behind.  Once you've done this job once you don't want to have to do it again!  Besides, it is a whole lot easier to get the speedo out if the tach is already out, and a whole lot easier to reinstall the speedo if you can reach through the tach hole when tightening everything up.

If you want to minimize or avoid scratching the painted dash, try applying some 3M blue painter's tape before starting to remove the instruments.
- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havana Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

DaveB

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Re: Tachometer 'Screech'
« Reply #4 on: January 17, 2021, 01:31:12 »
my mechanic detached the wiring to stop the screech.

ahh he gives me a great idea to solve my diff whine - detach propellor shaft.
DaveB
'65 US 230sl 4-speed, DB190

Pawel66

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Re: Tachometer 'Screech'
« Reply #5 on: January 17, 2021, 02:17:54 »
yeah... when my car is in the garage- nothing screeches... have not thought about it before!

Your mechanic probably detached the shaft, I see.

There is a procedure on how to remove the instruments here in the Technical Manual. Blue tape is a vey good tip. See via the search function what can be done once you have the dash disassembled - bulbs changed, etc.
Pawel

280SL 1970 automatic 180G Silver
W128 220SE
W121 190SL
G-class

DaveB

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Re: Tachometer 'Screech'
« Reply #6 on: January 17, 2021, 03:14:34 »
The protective tape is certainly a good tip. But perhaps an even less sticky version than blue, think it's purple? It would be so disappointing to pull off paint with the tape! Unlikely I guess. Also good advice is the if your 50-odd year old tach needs attention, your 50-odd year old speedo won't be far behind.

Pawel - Luckily I was sensible enough not to dismantle my car before storage. Only took out the radiator to completely drain the coolant. I shouldn't have even done that, as the rad would be better protected in-situ. If I dismantled everything I would be like a squirrel stashing nuts, might never find them again. Tip - when removing anything to work on, always screw the nuts & bolts back into place after (I'm sure you already knew that one). Also, I have not cleaned the driveline, it is totally covered in leaked oil and grime. Which is very effective corrosion protection, looks great beneath!
DaveB
'65 US 230sl 4-speed, DB190

GM

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Re: Tachometer 'Screech'
« Reply #7 on: January 17, 2021, 04:13:55 »
From my experience it's not so much the paint to worry about but the chrome plated trim over the gauges. The tach and speedo mount VERY close to that piece and can easily be scratched on removal and replacement. Ask me how I know... ::)
Gary
1971 280SL
180G Silver Gray Metallic
Black MB Tex

ja17

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Re: Tachometer 'Screech'
« Reply #8 on: January 17, 2021, 04:39:32 »
The steering wheel is easily removable. Remove it first and you will have plenty of room to work on the tachometer, without scratching the dash.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

cfm65@me.com

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Re: Tachometer 'Screech'
« Reply #9 on: January 17, 2021, 16:22:32 »
Pawel,
The screeching might be the cable.
I suggest, before removing the instruments, put a few drops of oil down the speedo cable. Take it around the block, another few drops and connect the cable. This might solve the screech problem.
Regards
Chris
Cape Town.
28 Ford Model A Pickup
29 Chevy Phaeton
67 E Type FHC
67 250SL 5 speed
83 911SC
2015 VW T5 California Pop Top

Pawel66

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Re: Tachometer 'Screech'
« Reply #10 on: January 17, 2021, 16:26:04 »
They unhooked the cable and it stopped....

But , yes, it sure can be.
Pawel

280SL 1970 automatic 180G Silver
W128 220SE
W121 190SL
G-class

stickandrudderman

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Re: Tachometer 'Screech'
« Reply #11 on: January 17, 2021, 18:15:08 »
Detach the tacho cable at the engine end, elevate it by attaching a piece of wire and hanging it from the bonnet, attach a small funnel to the tacho cable and add just a small quantity of light oil, leave overnight and then re-attach the tacho cable. Chances are your noise will be gone.
IMPORTANT: don't use any more oil than is necessary to lube the cable, otherwise it'll end up filling the tacho or dripping down from under the dash and spoiling your carpet! For extra insurance put a drip tray in the footwell.

jlimpic

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Re: Tachometer 'Screech'
« Reply #12 on: January 18, 2021, 14:15:16 »
Thank you for info Mike. 

Curious, would you take both out yourself?  if so, any directions you might be able to share?

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Mike Hughes

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Re: Tachometer 'Screech'
« Reply #13 on: January 18, 2021, 15:02:35 »
I did, and full instructions are found here:

https://www.sl113.org/wiki/Electrical/DashboardInstruments#DashboardRemoval

Once you have removed your instruments do not proceed with the disassembly steps.  Carefully package them up with bubble wrap, etc., and ship them off to Palo Alto (Call them first, to set up the service and for shipping instructions).  They will disassemble, clean and service as necessary, and return them to you freshened up and looking like new.

While you are waiting for your instruments to be returned from Palo Alto, I would recommend spending some time strolling through and familiarizing yourself with the Technical Manual.  It is a tremendous resource for a Pagoda enthusiast.  You can find the Technical Manual link directly below your name in the upper left hand corner of this web-page.  Armed with a little knowledge you will likely be able to tackle other projects in future.  Next to driving it, working on it is the best way to bond with your Pagoda. ;^)
- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havana Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

ctaylor738

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Re: Tachometer 'Screech'
« Reply #14 on: January 30, 2021, 22:22:16 »
I just got my 230's screeching tach back from North Hollywood Speedometer.  I've sent them a number of tacos, speedos, and clocks for repair in the last couple of years.  I have found their work to be excellent and their turnaround time and customer service better than Palo Alto.
Chuck Taylor
1970 280SL #13027 (restored)
1966 230SL #15274 (sold)
1970 280SL #14076 (sold)
Falls Church VA