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Audi ur-quattro 1988/9 MB Engine - Notes to circuit diagrams

• Audi's index doesn't pick diagrams for either the electric windows or the heated seats. Diagrams 25 and 26 have been consolidated with minor amendments.
• The headlight washer circuit is illustrated without its components. The relay sits in the main panel position 4 but is not documented in any diagrams.
• Information on the lockable centre differential is still present in the main diagrams, though the feature was deleted for the 1988 model year.
• The cruise control diagram refers to the distance sender (vehicle speed sender) as G54 - the main diagram and digital dash diagram refer to G22. There is only one sender on the car.
• The digital dashboard diagram refers to J150 as an 'oil warning delay relay'. In fact the MB uses J114, the switchover relay that sounds a buzzer for oil pressure problems over 2000 rpm. The purple (lilac) wire carries an rpm signal.
• The digital dashboard designations for the foglight and rear foglight warning lights override the ones in the separate feature diagram - the latter have been deleted as not fitted to UK cars.
• The digital dashboard schematic wrongly identifies K64 as the hazard flasher warning light. In fact this is K6 in the main diagram - K64 is the right hand indicator warning light.
• The wire between N70 (track 43) and N (track 45) is labeled as 'red'. On all cars so far seen, this wire is black/white.
• The idle stabilisation valve N66 is identified in the diagram (track 50) as N71.
• M4 (track 126) is identified as L4 in the index.
• V (screen washer pump) is in track 156, not track 137.
• Diagram 41 identifies K19 as a seat belt warning light and K21 as an OXS sensor warning light. Neither is fitted to the MB.
• The index incorrectly picks Diagram 36 for the radio "up to December 1988". This should read "up to September 1987" - the change was to remove the link to the voice synthesizer, which was never fitted to the 1988/9 model year. Diagrams 45 and 46 should be picked for all MB-engined cars.
• The digital dashboard does not distinguish between the functions of Pins 26 and 27, which are both connected to G3, the coolant temperature display. Pin 26 is connected via a blue/brown wire to G2 on the side of the head and drives the temperature display. Pin 27 is connected to the multi-function thermoswitch below the head water union and to the coolant level switch - if either switch closes the top three segments of the display flash as a combined warning of either overheating or low coolant.
• The multifunction thermoswitch (F76; tracks 202-204) can cause confusion. The loom was designed to provide it with two separate power supplies, one for each function. As shipped, however, only one of these supply pins - labelled "+" on the sender - is actually used. The other supply pin - "T" - is not used and the black wire coming from the connect is cut off in the loom. The diagram marks this black wire with an "*" and the note in the index says: "Leitung ohne Funktion - dient nur zur Abdichtung" or "Non-functional wire - serves only to seal". This is fine for the thermoswitch shipped with the car - 035 919 369L. This has long been obsolete, and replacement thermoswitches (034 919 369C) only have three pins. The deleted pin is however the one marked "+" - so if a three-pin thermoswitch is fitted to a stock unmodified loom neither power pin is connected. The solution is to splice the black wire (track 202) into the black/blue wire (track 204).

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