I NEED A NERD!

[Chadick]

I have a metric KPH instrument cluster in my 1997 850R. This is a daily driver so I switched out the instrument cluster with a speedo reading MPH. I picked up an extra cluster and broke down both clusters to swap the instruments panel alone (including all potentiometers (pots)). Both speedo pots had the same model number on them with a date stamp of late 95 for the replacement. I believe I read something regarding early 1990s cluster may not work correctly in a 1997.

My thought was the original metric board would tell the same pots what to read, with the KPH under the MPH on the speedo dial and all is good…

On the first test drive the speedo accumulated positively. Below 40mph, the accuracy is close, but accumulating. Above 40mph, +10MPH over 50MPH. Have yet to drive the car above 65mph for data collection. The kph was just as inaccurate.

I swapped the original metric pot with the transplanted pot and received the same result. Lightly sanded and cleaned the contacts, same results. Reset the hand and received the same result. Unplugged the battery to attempt to reset the CPU. Same result.

Found a technical document for a 1992 850 talking briefly about the 48 plus of a speed sensors and resetting the regional setting when replacing the cluster, with nothing more.

Not sure if the speedo was accuracy in the first place, as I’m am metrically challenged.

Does anyone know if the is some way to calibrate the replaced speedo? Or should I be barking up the wheel speed sensors tree?

Thanks for the read.

[xanthefin]

There is tire size parameter programmed in speedo (VDO) which affects your speed gauge how much it shows. Maybe its different?

[yanga001]

Agree with Xan in terms of the tire size. Are you running standard tires on the car? take some standard data points every 10 mph and plot the inaccuracy to see if it is a fairly constant error percentage. I think google maps will tell you your speed as you drive so you can use that for reference. In terms of the cluster itself, i seem to recall a pulse per revoloution signal was fed to the cluster in order to calculate the speed (for 98 v/s/c70's). They also had some outputs to the radio and electronic climate control (ECC) for adjusting intensity based on speed.

If you have a Vag Com KKL cable kicking around then maybe you can use VOLFCR to read out some of the parameters from the car. Its been a few years since i drove my V70 but maybe you can check the speed parameter of the car and cross reference that with reported speed and measured speed. If the measured speed is accurate on both the cars parameter and the google maps, but inaccurate on the dash then it probably is some out of calibration setting. If the parameter speed and the cluster speed match then i would look elsewhere. You can physically calculate the speed using the wheel speed rpm and multiplying it by the circumference of the wheel. ie = miles/meter* meters/rev (From circumference) * revs/minute *minute/hour. This should get you the vehicles measured speed from the wheel speed in revs per minute.

It is not a direct answer but i hope its a starting point.

[Chadick]

Working with KPH and MPH.

Just got the 850 OBD app up and running! Found the wheel size set to standard and changed it to a custom circumference. It appears speeds up to 70mph (+/-2) agrees with the GPS!! I did notice the original metric cluster removed from the car had been professionally repaired. Never ready confirmed the speedo was correct before starting this process. Any ideas how this setting could be lost?

While running live data in the 850 OBD app, I noticed the displayed (ECU?) speed 5 to 10 kph faster than GPS and speedo displayed speed. And noticed the tach showing an ideal speed of 910 rpm when the ECU showed 832 rpm (which is where it usually sits). Stomping on the throttle, the RPMs go up to 9000rpm!! ECU shows something around 5000 rpm. Have not found the tach settings are yet. I might have causes the tach issue tinkering with this app.

Any experience with this app or what I should be looking for to correct the tach?

[scot850]

Why did you swap everything over? I took a 97 850 NA to US from Canada and just swapped the whole MPH unit into the KPH car and it worked fine with no issues?

There were 2 brands of clusters used in the mid 90's 850's.

Neil.

[Chadick]

Trying to get a speedo with MPH. The donor cluster was from a 96 turbo.

Are you suggesting I carry over the tach potentiometer?

[scot850]

Did your replacement MPH cluster come from a non-turbo? Otherwise, if it is, the only real difference is the turbo boost gauge on the turbo cluster that naturally is not in the NA version. If this is the reason for doing all the swapping, I can now understand all the work you are going through. Other than the turbo gauge you can just swap them over complete.

If your MPH version is from an NA, then you can still use it complete but you lose the turbo boost gauge.

Neil.

[xanthefin]

Working with KPH and MPH.

Just got the 850 OBD app up and running! Found the wheel size set to standard and changed it to a custom circumference. It appears speeds up to 70mph (+/-2) agrees with the GPS!! I did notice the original metric cluster removed from the car had been professionally repaired. Never ready confirmed the speedo was correct before starting this process. Any ideas how this setting could be lost?

While running live data in the 850 OBD app, I noticed the displayed (ECU?) speed 5 to 10 kph faster than GPS and speedo displayed speed. And noticed the tach showing an ideal speed of 910 rpm when the ECU showed 832 rpm (which is where it usually sits). Stomping on the throttle, the RPMs go up to 9000rpm!! ECU shows something around 5000 rpm. Have not found the tach settings are yet. I might have causes the tach issue tinkering with this app.

Any experience with this app or what I should be looking for to correct the tach?

Hi, tacho setting of the COMBI aka Instrument Panel is related to Country Code parameter hex code which has being either Diesel or Petrol ( 5k vs 7k RPM range).
It has bit which tells which one it is. There is no other related options in my knowledge and this does affect how RPM is shown different places. There is no any general need to change Country Code parameter if else known reasons due there is multiple things related to its value.

This tacho relation is explained in Country Code window Below !WARNING! text.

Its reversible to program back what originally was there. It only accepts certain valid values programmed. On 70 series it can funnily start showing kilometers instead of miles if program values crossed by guessing.

Edit: i was bored enough.. IF you did change Country Code.. its possible should be 850R "A4" in hex format for you (US).
Edit2: Its for me known example the speedo on 850 is very not exact in changing enviroment.. like i feel in up hill speed slowing down (in butt GPS/Galileo) but speedo still pointing same so there is lag / hysteris / spring effect on speedo needle what you see.

Edit3: Here little preview after night coding and head scratching from next version of the App from COMBI's Country Code parameter programmer with little helping hand what to put there so helps to avoid most of problems in future. P.S. The labeled "Unknown bits" is mostly on 70 and 40 series COMBI's. Dont ask i dont know (yet).

[misha]

What about a trick with hours & minutes buttons on board computer on instrument cluster?
When you press them both in the same time...temperature and mileage should convert to F instead of C and mileage reading should go from km/h to miles.

The same should be for speedometer.

[xanthefin]

What about a trick with hours & minutes buttons on board computer on instrument cluster?
When you press them both in the same time...temperature and mileage should convert to F instead of C and mileage reading should go from km/h to miles.

The same should be for speedometer.

-Selecting units at Trip Computer:
Once means pressing hour or minute button
Press once: 12-hour clock and F
Press twice: 24-hour clock and F
Press three times: 12-hour clock and C
Press four times: 24-hour clock and C
..
Press finally both hour and minute buttons (5 seconds or so) to save and apply the settings


This is for 850 COMBI / Trip meters.


As previously mentioned on 70 series they can change at least by programming the kilometers/ miles.. well i know because i got more than once people contacting me after changing the parameter how to change it back when they forgot the original default value and they dont get it any way back to show kilometers / miles in trip meter. So i belief they tested this trip meter buttons too on 70 series but i can be wrong of that detail

99 year models/ late P80 models with CDM Instrument panel/cluster.. i didnt yet check any details. Later if someone needs those for something. Some things at least programming is protected by PIN code on those.