help with instruments

[deQuincey]

hi, i am renewing the instrument panel and i have a couple of questions:

1- what is this small metallic plate for ? is it a mechanic fixing ? or an electric connection to ground ?

2- you can see in the next pic the bottom of the speedo clock, can you tell me if this model is appropriate for a 4-speed 1971 e9 3.0 CS ?

i start this question because my actual speedo is giving me wrong reading of the car velocity, so i want to know if this new speedo (i have no history of the donnor car) will be a good replacement or if i will meet the same problem

specially the W=0,7125 is that the correct ratio ?

3- i have painted the metallic base plate, to avoid future corrosion, (the original status is a galvanized finish that has dissaperared in the edges (as is a common case when you cut or drill galvanized steel))
but i am wondering if this is not correct because i might be isolating some electric conexion to ground. really i don´t think so because each clock has a dedicated ground conexion, but just by the case i make the question

i will appreciate all your kind answers

best regards

 

[deQuincey]

any help ?

thanks

 

[JhwShark]

My curiosity is up on this as well...

Grounds to the cluster are usually through the Brown wires attached to the instruments back housing.

 

[61porsche]

Instrument panel and Speedo

Looking closely at the wiring diagram, the brown wires do ground in several ways as well as the panel. The small tab serves both to fix the panel and a ground. As many have reported when they've had issues, it's best to run another seperate ground. In my opinion, it would be to the metal backing panel.

Speedo- BMW to this day, admits that a speedo can be off as much as 10% before there is a warranty issue!

Usually and because E9s are mechanical, the problem is with one or both of two gears. ( Worm and circular.) There are suppliers for the gears that crack, missing/ broke a tooth, or changing ratios. Most the time the guage would have exhibited some distress or noise. Sometimes the gears just slip on the shaft and a judicous application of epoxy or super glue can fix the problem. There are instances where the needle goes further south of the fixed point and has to be reset.( pointer out of range.)

Perhaps an explanation of the what the guage is doing or not would help...

FYI- VDO has begun introducing a combination electrical and mechanical speedo conversion that looks promising for electrical output transmissions that will directly interface with a mechanical speedo avoiding all the differential conversion signal issue and can be reset for different ratios by using a button and a marked mile distance. Looks promising to me for future 5 speed swaps.

 

[MMercury]

what is this small metallic plate for ? is it a mechanic fixing ? or an electric connection to ground ?

Nice job with the restoration.

The tang you highlighted does not appear to be a typical grounding point. This could have been more easily accomplished by an eyelet connection to any one of the preexisting posts or attachment locations. As you will note from the above picture (taken from the shop manual), no tang is present. That doesn't mean tangs weren't later additions.

I suspect a better explanation for the tang is that it was merely a makeshift design to secure the bundled wiring.

hth

 

[Stevehose]

According to an old post on this forum, the picture of this cluster frame has the tang:

 

[MMercury]

According to an old post on this forum, the picture of this cluster frame has the tang:

This may have also been described as an "arm" in this thread: http://www.e9coupe.com/forum/showthread.php?t=5075

Whether it was an original attachment to all E9 instrument clusters, or a later factory addition, its purpose remains unclear (to me).

From this perspective, it almost seems like it might be used to secure a gauge - or as a locking strip to secure the housing to the body. Granted, the fact that it is straight with squared edges suggests it would not be the best means of securing the wiring that passes near it.

 

[Gosch]

the mystical of w=mark´s

Hi,

read the thread : http://www.e9coupe.com/forum/showthread.php?t=2464

 

[deQuincey]

thanks to everyone !

now i can see that the W is ok for my 3,0CS, i hope it works ok and no gears are damaged !

i agree that the tang can be avoided as a ground, basically think that apart from the dedicated grounds in each clock (brown cables), the two attachemnt points to the body, will do ground through it´s threads !

i am not sure but when i replace the instrument panel in the car, i will see what i can do with that tang

 

[deQuincey]

hi, a question to mr,mercury, or to anyone that can help:

can you see the big difference between the conexion cable that can be seen in this old picture, and mine ?

what am i supposed to see when i open my car dasboard ? the long one, or the short ?

i am mainly worried about the conexions, are they going to be the same ?

regards

 

[Arde]

thanks

On the wrong speed reading question, I wrote in the past but I can' find it. Here is my view, you can determine if the error is an offset vs. a factor by measuring the error at different speeds. I assume you use your GPS as the master reference. You can measure at 20, 40 , 60, 80 and if the error has a multiplicative factor (error increases with speed) then the W, the tires, and the differential all combined create a factor different than 1, and then can go figure out why.

If you have mostly an offset (error does not increase with speed above some minimal speed) then you can think of it as the instrument faceplate being rotated a bit. I do believe BMW deliberately built an offset into its mechanical speedos to make sure the error is biased to the safe side. You will not exceed the speed limit, your acceleration appears to be better, your oil changes will be more frequent, and your tear and wear all look better. I find such an "optimistic" offset of that type in all three I own (E9, E24, E36).

 

[MMercury]

Can you see the big difference between the connection cable that can be seen in this old picture, and mine ?

what am i supposed to see when i open my car dashboard ? the long one, or the short ?

i am mainly worried about the connections, are they going to be the same ?

Hello,

Did not intend to mislead you with the picture from the shop manual. My focus was on the mystery "tang" rather than on the wiring.

BMW changed many things on the E9 during its manufacturing lifetime and this includes the wiring harness. As a cost/labor saving measure, the newer models had electrical couplings like yours. This presumably made removing and installing accessories and switches easier to manage. In my limited experience, all of BMW's later models used modular, molex or molex-like connections. And, as the years have progressed, even those connections have evolved from "pins" to "spades" to "whatever" and back again. It is a matter of opinion as what works the best and last the longest. Just compare the your fuse styles with those used today, as but one example of change. :wink:

For what its worth, your wiring looks correct to my bleary eyes.

hth

 

[deQuincey]

Perhaps an explanation of the what the guage is doing or not would help...
.

some explanations:

i don´t use a gps, but a friend of mine was in another car behind me, telling me the speed by the phone :-?

roughly speaking i think that the figure in the speedo is more or less half of the real speed (consider also the deviation of his speedo)

no apparent noise can be heard in the speedo while driving, so if a gear is faulty i can not tell

anyway my intention is directly interchange my old speedo with the (1974´s) new one

regards

 

[deQuincey]

Hello,

Did not intend to mislead you with the picture from the shop manual.

hi, no misleading, don´t worry !

i was only asking if in your opinion, my car (1971) will have the old wiring harness (like in the shop manual) or the new one (like in my renewed 1974`s panel)

maybe i have to remember that i do know nothing about what is inside my car´s instrument panel ! (all the pictures about a renewal of instruments is of a donnor instrument of a 1974 car)

regards

 

[MMercury]

I am not an E9 scholar respecting the chronology of BMW's wiring changes. An uneducated guess is that the photo used in the Shop manual is of a gauge cluster from a 2800cs. Yours, from a 3.0cs looks typical and correct.

The more things change, the more they stay the same. Here are some more instrument clusters you can dream of refurbishing. :wink:

 

[Arde]

some explanations:

i don´t use a gps, but a friend of mine was in another car behind me, telling me the speed by the phone :-?

roughly speaking i think that the figure in the speedo is more or less half of the real speed (consider also the deviation of his speedo)

no apparent noise can be heard in the speedo while driving, so if a gear is faulty i can not tell

anyway my intention is directly interchange my old speedo with the (1974´s) new one

regards

Only two explanations for a 50% error: 1) the instrument/speedo cable are shot 2) your friend is playing a practical joke on you.

I would try to replace both the instrument and the friend, just in case.

 

[deQuincey]

Only two explanations for a 50% error: 1) the instrument/speedo cable are shot 2) your friend is playing a practical joke on you.

I would try to replace both the instrument and the friend, just in case.

;-)
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;-)
very wise !