Author Topic: Tach Installation Nightmare  (Read 2793 times)

Atazman

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Tach Installation Nightmare
« on: June 23, 2020, 04:24:56 »
Hi Pagoda family….

Age has taken a toll on my agility.  Nonetheless, I needed to get the tachometer out to properly ground my instrument lights.  It was not too difficult reaching up from behind and unscrewing the nut securing the tach bracket.  But reassembly was a nightmare!  Definitely not easy getting the tach back in the hole, the “U” bracket aligned, and then the retaining nut back in place.

After it was all said and done, I’m thinking there is a way to assemble the “U” bracket onto the tach and even installing the retaining nut while the tach is out in front of the hole.  Then…. just stuff the entire assembly into the hole.  Here’s the thought……….

Using spring steel, make a new/different “U” bracket that will fit through the dash hole.  Shape it so that the ends of the “U” spring outward, slightly wider than the hole.  After installing on the tach, start the retaining nut.  Once partially inserted into the hole, the bracket should be “springy” enough to where the sides can be compressed to slide into the hole ahead of the tach.  Once inside the hole, the sides of the “U” would spring outward and hold the tach in position.  All that would be needed from the backside of the dash would be to tighten the retaining nut with your fingers. 

Tach removal would be no different than now; we have to reach behind the tach and remove the retaining nut.  The “U” bracket is taken out through the hole after the tach is removed. 

If I would have dreamed this up before my installation today, I would have cut the existing “U” bracket to reduce width, bend it slightly to get some spring action, and weld it back together as a trial.  I might have had something positive to report.  Also, I’m guessing the job would be easier if the threaded rod on the back side of the tach is longer.  That would be no problem to change.

Too late now but maybe next go around.
Don
67 250 Sl
(#3168) from Italy
5-speed/Posi/AC/Kinder

ja17

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Re: Tach Installation Nightmare
« Reply #1 on: June 23, 2020, 05:21:42 »
The steering wheel can be removed easily to make the job much easier. Did you remove the wheel?
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

WRe

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Re: Tach Installation Nightmare
« Reply #2 on: June 23, 2020, 07:55:23 »
Hi,
steering wheel AND driver seat removal, laying backwards on the floor (with some pads leveling the floor) can make it a liitle bit easier.
But now as ever it's a lousy job, I can't image how it was done during production, even when heating levers were still not build in.
...WRe

Jonny B

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Re: Tach Installation Nightmare
« Reply #3 on: June 23, 2020, 14:35:43 »
I will second the idea of taking out the seat. I just had to tighten two steering column bolts that are behind the dash. I took out the seat and the steering wheel, and used towels as padding. Fortunately all I had to take out this time was the tach. Fortunately I have smallish hands and was able to get the tach back in place with minimum swear words.

I have had the whole dash apart including the heater controls, NO FUN AT ALL!
Jonny B
1967 250 SL Auto, DB 568
1970 280 SL Auto, DB 904
1966 Morris Mini Minor

ja17

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Re: Tach Installation Nightmare
« Reply #4 on: June 23, 2020, 16:22:42 »
Actually there is a bulkhead between the heater controls and the dash instruments so with removal of the heater controls, the job is not any easier. Experience and correct sequence of dis-assembly and aswsembly seems to be the biggest factor.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

Peter

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Re: Tach Installation Nightmare
« Reply #5 on: June 23, 2020, 18:25:30 »
When I have to take out/mount the dash instruments I first take out the left Chrome Cover plate of the ventilation and the air duct behind it. To be honest I did not mount the (left) air duct, so in a minute I’m able to easily take out or mount the tachometer, speedometer and Instrument Cluster.

Atazman

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Re: Tach Installation Nightmare
« Reply #6 on: June 25, 2020, 16:25:38 »
Thanks to all for your comments and suggestions.

Yes....."back in the day" I was able to remove/install the dash instruments.  I always removed the seat but never the steering wheel.  Also, I never thought of removing the air duct to the left as pointed out. 

Before I go through this again, I will find out how to remove the vent and air duct tube.  My assumption from Peter's note is that the nut and bracket behind the tach can be reached through the air duct hole.  That sounds like a good plan.

Also, I would like to experiment by using a spring steel bracket, as I mentioned initially, to enable installing the complete tach assembly from the front of the dash.  If anyone has one of these brackets for sale......please let me know. 

As always..... I appreciate your feedback.
Don
67 250 Sl
(#3168) from Italy
5-speed/Posi/AC/Kinder

Peter

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Re: Tach Installation Nightmare
« Reply #7 on: June 25, 2020, 17:42:46 »
Before I go through this again, I will find out how to remove the vent and air duct tube.  My assumption from Peter's note is that the nut and bracket behind the tach can be reached through the air duct hole.  That sounds like a good plan.

Correct.

The chrome is fixed with two round clips. (see picture).
Use a soft material such as wood to gently pry it loose from the dashboard.
The airduct is fixed with, I believe, 2 screws to be reached from the underside.
Via the hole you can reach the three instruments form behind.

When the clips cannot be used anymore for fixing the chrome you can also use a screw plug (in Europe: Fischer SX 5x25K). These plugs are much less expensive than the clip of € 11.


Atazman

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Re: Tach Installation Nightmare
« Reply #8 on: June 26, 2020, 00:50:22 »
Peter,

I thank you for the good info!!  And thanks for the picture too.
Don
67 250 Sl
(#3168) from Italy
5-speed/Posi/AC/Kinder

mrfatboy

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Re: Tach Installation Nightmare
« Reply #9 on: June 26, 2020, 01:04:45 »
I threaded the post and just put a nut on it.  Much easier the next time I have to go in.  It has already come in handy🤣
1969 280sl (Aug 1968 build)
Signal Red
4 Speed

prefervintage

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Re: Tach Installation Nightmare
« Reply #10 on: June 26, 2020, 01:22:10 »
What die was used to thread the vent posts to accept nuts, may I ask?

mrfatboy

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Re: Tach Installation Nightmare
« Reply #11 on: June 26, 2020, 01:24:34 »
I had a metric kit from Harbor Freight.  I seem to remember it was 4mm or 5mm.
1969 280sl (Aug 1968 build)
Signal Red
4 Speed

66andBlue

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Re: Tach Installation Nightmare
« Reply #12 on: June 26, 2020, 05:06:03 »
....
Before I go through this again, I will find out how to remove the vent and air duct tube.  My assumption from Peter's note is that the nut and bracket behind the tach can be reached through the air duct hole.  That sounds like a good plan.
...
In addition to removing the round clips shown in Peters photo the chrome plate is also fixed in place by a hook which I have always found to be the most difficult to keep intact when you pry the cover of.
Here is a photo:


You can also use speed nuts instead of the round clips, they are a lot cheaper.
https://www.sl113.org/forums/index.php?topic=7690.msg48830#msg48830


Alfred
1964 230SL manual 4-speed 568H signal red
1966 230SL automatic 334G light blue (sold)
1968 280SL automatic (now 904G midnight blue)

Atazman

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Re: Tach Installation Nightmare
« Reply #13 on: June 27, 2020, 18:37:50 »
Thanks, Alfred, for the additional tip on the chrome vent also having that hook tab on the back side that must be disengaged.

I'm still intrigued by the thought of modifying the tach bracket to be able to slide the whole tach assembly in from the front and then just tighten the knurled nut on the backside.  Maybe one of my new LED bulbs will fail and I will get the opportunity to prove my insanity.

Thanks for all the other options (everyone) that we know have been tried and they are "true".
Don
67 250 Sl
(#3168) from Italy
5-speed/Posi/AC/Kinder