the myth about the cluster engine coolant indicator
There were in the past a lot of discussions what is right or wrong when the temperature gauge on the cluster temperature indicator is right or left of the 12 o' clock mark.
The truth/fact is:
Temperature indication on the BMW is not linear, they call it 'tableau', basically the indicatior at 12 o'clock can mean everything between roughly 75-110 degree Celsius. Everything in between 75-110 is just 12 o'clock. Plus/ minus 1-2 mm to the right or left (deviation caused by the parts installed).
The analog signal ist processed in the instrument cluster and compared with data in the coding plug. A corresponding signal is sent to the instrument. Five temperature support values are stored in the coding plug.
Exceeding the temperature limit stored in the coding plug will additionally send corresponding warning information to the check control and display it there.
That is written and shown here on page 4 of the instrument cluster check control training reference book http://www.e38.org/e32/BMW_pdfs/INST_info.pdf
What is NOT shown in the English version I found in the German version, here a copy of that page showing the temperature diagram curve in picture 14, and there you see the socalled 'tableau' between 75-110 degree Celsius.
20 Photo by shogun_bucket | Photobucket
In the cluster chip the following data are stored (German language)
1. Gesamtwegstrecke km/miles
2.
SI-Stand
SI-Zeit
SI-Grenzwerte
3. Code-Nr. des Codiersteckers
4. Verbrauchskennlinie
5. Wegimpulszahl
6. US/ECE -Ausfuehrung CC III
7. Tank /5 Stuetzpunkte (Liter/Anzeigewerte)
8. Kuehlwasser-Temperaturanzeige/Stuetzpunkte
9. Kuehlwasseruebertemperaturgrenze
10. Grenzgeschwindigkeit (Limit)
11. Ton-Trigger-Ausfuehrung
12. Reserveraum fuer Fahrgestellnummer
13. Zylinderzahl
14. Programmanzeige ausblenden
15. Landessprache CC III
16. Gesamt-KM-Zaehler-Offset
17. Programmkonstanten
The English version of the handbook again does not mention all those, just a few:
Examples of NV-RAM Contents:
total odometer mileage
SI information
code number of coding plug
fuel gauge support values
temperature gauge support values
number of cylinders
This was confirmed by someone from the German 7-forum who is expert in cluster chips reading and programming.
In his words:
Die Kühlmitteltemperaturanzeige ist nicht linear. Wenn die Kühlmitteltemperatur in einem Bereich zwischen 75°C - 110°C liegt, steht die Anzeige Punkt Mitte. Erst ueber/unter diesen Werten sieht man eine Veraenderung der Nadel. Dies ist ein von BMW beabsichtigtes "Tableau"-Verhalten.
This is completely different from my Honda truck which basically shows always too low temperature for my feeling, as I am used to my BMW info. I would interprete it in such way, that BMW wants to have a stable indication for the usually non technically oriented average driver, and only warn when absolutely necessary.
