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Discussion Starter #1 (Edited)
Hi All,

I'm just in the process of rebuilding a S4 Spider Speedo (Euro version RHD) I have just sorted out the electrics at the back of the unit and I would like to match the donor unit mileage to the actual cars mileage (one being in KM and the other in miles). Now I know taking these things apart can be a real nightmare but do any of you know how to do this?

I am thinking that removing the small electric motor at the side and using the toggles at the top to wind back the dials …. or am I completely off piste?

A fellow S4 owner also tells me that the dials possibly can only be wound one way?

Does anyone have any ideas how this can be achieved?

The other question is … would it matter if the donor speedo is imperial and the one it is replacing is in KM as 1mile is about 1.6KM …. would the electrical circuit boards be compatible with each other or would a KM circuit board still try to produce KM's on an imperial odometer?

All your thoughts would be very gratefully received.

P
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don't break those tiny green and red wires on the odometer's stepper motor (your 1st photo)...they are almost impossible to solder back on w/o melting everything.

not sure what you are aiming to do: are you going to replace that rather dirty one with the red felt tip marks at 50, 65 and 112 (92518 on odometer) with the dual 'mph/kmh' one (91362 on odometer)?
I believe the odometer reads KMs even on the speedos marked mph/kmh (another quirk of converted cars)

why don't you just drop in the new speedo... the 1500 km difference between the two odometers is hardly worth the risk of damaging the new speedo
(of course you don't know if the new one works, and if it does work, how slow it reads....till you test it)

someone else might have ideas.
 

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Discussion Starter #4
Yes I get where you are coming from re the wires …. bearing in mind gearing tends to wear together, I wonder how wise it would be to drop the little electric motor into a donor unit or vice versa. I also wonder if a KM circuit board would do the same readings placed into an imperial speedo (and vice versa)

Once reassembled I also think it may also be a good idea to send the units out to Speedy Cables | Automotive Instrument Repair - Mechanical Cables for recalibration and refurbishment.

Yes now you mention it the 1500 km difference between the two odometers is hardly worth the risk of damaging the new speedo. That said it is a real pain to drop in an ODO that you don't know whether it is working or not so sending out seems like an even better idea.

There may however be people out there that have re-adjusted the mileage and views would be very gratefully received.

My real concern however is whether dropping in an imperial unit will give accurate mileage readings if the set up is for KM. Maybe if I keep the circuit boards for the particular speedo attached to the original unit it will not matter?

I am of course interested in your knowledge and experience!

P:)
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Discussion Starter #5 (Edited)
All,

Would I be right in assuming that as the unit receives 12V whether the odometer reads miles or KM that either unit would give an accurate reading of the distance covered whether it be kilometres or miles on my Euro S4?
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Rebuiding a speedo is virgin territory for me so would be brill to know from those of you more experienced.



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it actually runs by impulses from the impulse generator mounted on the chassis near the exhaust downpipe...
and the impulse generator (#3 in diagram) has the same PN for all S4 spiders, be they USA, CAN or EU delivery cars.
(The connector from pulse generator #4 is up near the brake booster, just for info)

speedo.jpg
I believe there should be a paper tag on the back of the speedo case with some info?

btw in that last photo of yours you can sees the speedo adjustment screw (the one with a blob of silicone on it from the factory)...that is what you use to calibrate the speedo if it is not reading correct (say against a sat nav)

this is a long thread on the electronic speedos/tachos which might help
How to fix your slow reading speedometer or tachometer on 91-94 Spiders
 

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Discussion Starter #8
Just taken delivery of a KM speedo for re-building … has anyone got any thoughts on what should be fitted. I did promise I'd keep the car original to the previous owner but would the speedo still read in miles if I re-fitted that?

P
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So you'll note the that the mph and kph speedos just have different faceplates: the needle moves to the same point at the same speed on both of them. The 100 kph point on the mph speedo is the same as the 100 kph point on the kph one.

I believe the difference in the odometer is that they have a different drive gears but don't quote me on that.
 

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Discussion Starter #10
That's interesting ! …. so the original drive motor should go with the original speedo .. I get you !! but would changing the metric Odo circuit board for an original imperial circuit board affect the readings?

In other words it sounds like keeping parts to an Odo to that particular Odo makes good sense.

P
 

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Discussion Starter #12
All,

This could be a very interesting journey!! I am thinking of going down the route of a reproduction speedo (which can incorporate original parts and are indistinguishable from the originals externally (and most certainly would be much more reliable)

There is a firm that does this in the U.K. called https://speedycables.com/ They do government contracts and have a fantastic reputation. I think I will be giving them a call. Be advised though they are reputedly slow and have a staff of 20 to service a world wide demand … yes I think I will give that avenue a try ...

P
 

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All,

This could be a very interesting journey!! I am thinking of going down the route of a reproduction speedo (which can incorporate original parts and are indistinguishable from the originals externally (and most certainly would be much more reliable)

There is a firm that does this in the U.K. called Speedy Cables | Automotive Instrument Repair - Mechanical Cables They do government contracts and have a fantastic reputation. I think I will be giving them a call. Be advised though they are reputedly slow and have a staff of 20 to service a world wide demand … yes I think I will give that avenue a try ...

P
Hi Andrew, I don't want to put you off but I tried Speedy Cables years ago for help with my S4 speedo and they couldn't do anything with it. And are VERY slow.
Whereabouts are you in the UK? I gained a bit of knowledge sorting mine out, and have a couple of spare speedo units, if you do some accidental damage to yours! I'm near Harlow, Essex.

You can turn the numbers on the odometer if you undo the 2 screws holding the motor in and lift it off the cogs which turn the numbers. As Dom says, be very careful of those thin wires as they are fragile.
 

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Discussion Starter #15
Hi Andrew, I don't want to put you off but I tried Speedy Cables years ago for help with my S4 speedo and they couldn't do anything with it. And are VERY slow.
Whereabouts are you in the UK? I gained a bit of knowledge sorting mine out, and have a couple of spare speedo units, if you do some accidental damage to yours! I'm near Harlow, Essex.

You can turn the numbers on the odometer if you undo the 2 screws holding the motor in and lift it off the cogs which turn the numbers. As Dom says, be very careful of those thin wires as they are fragile.
In what way could they not help? … I am considering asking them to make a reproduction electronic version of the speedo ...

P
 

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I am considering asking them to make a reproduction electronic version of the speedo ...
I am not getting why one needs to do this?
these things are all repairable, and once repaired should last another 20 years....(or about how long it'll take speedi to make one for you;))
 

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Discussion Starter #17
I am not getting why one needs to do this?
these things are all repairable, and once repaired should last another 20 years....(or about how long it'll take speedi to make one for you;))
One needs to re-build as the original KM metric one is particularly *Fu barred :)

Interested in your repair !!

P
 

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Discussion Starter #19
Ahhh the little electric motor and disconnecting to wind the numbers to the correct mileage … did you have any problems when you did this and will the dials only wind in one direction?

Did you use the little toggles at the top to do the winding back?

Very appreciative for your advice !! P
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In what way could they not help? … I am considering asking them to make a reproduction electronic version of the speedo ...
I sent one to them wihich wasn't working accurately and, after some time and a charge of £40+ (it was some years ago, I forget the details), they sent it back still not working and did the equivalent of a shoulder shrug when I called to discuss.
I fixed it myself (actually with the assistance of a friend who is very handy with a soldering iron) by following one of the great threads on this BB, and putting a new variable resistor in.

I didn't change the numbers on my in-use speedo, I just experimented with a spare which is dead anyway. As I recall the wheels would turn either way but I will confirm this when I'm back home.

Andrew, I will PM you my phone number.
 
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