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ISO & DIN Radio and Satellite Navigation Connections

The radio is the worst documented feature of the Audi ur-quattro. Because of Piech's dictum that a sports car is "a car in which it is pointless to fit a radio"? Or it reflects an attitude gulf between Germany and the UK - Germans refuse attempts to "foist inferior radios on them at silly prices" (and there is legislation on the subject there) whereas Britons object to "a high-priced car without a radio".

Despite the availability of the stunning Philips MCC, UK ur-quattros were fitted with distinctly inferior Blaupunkt Toronto SQR 44s. These used the DIN system - a four-pin plug for power, ground and aerial control, with a separate pin-and-blade plug for each loudspeaker. Fitting a modern top-line radio, CD changer or satellite navigation system requires rewiring the radio connections to the ISO 10487 standard.

ISO 10487 Car Radio Connections

ISO car radio connectors - back of radio or cable side of connectors

In the UK, excellent connectors are available from Halfords or Nexxia. There may be up to four - connectors A and B are mandatory and often formed as a single block.

• Connector A is often not fully populated since some pins are used only by satellite navigation systems. Audi part number 000 979 225A is a wire with the correct pin crimped onto both ends - it just pushes in to the connector from the rear.
  
  
  • Pin 1 - GALA - Geschwindigkeitsabhängige Lautstärkeranpassung - speed-dependent volume control.
    
    This pin is used in some radios to increase the volume automatically at speed. It needs input from the speed sensor - more correctly known as the distance sender. The signal can be taken from the electronic dashboard or cruise control, if fitted. In the MB and RR ur-quattros, it can also be taken from the rear differential lock controller or the idle stabilisation computer. The wire is usually coloured red/yellow. When a cable speedometer is fitted and the car does not have cruise control (some early analogue dashboard cars) a separate wheel sensor must be fitted - e.g., Bosch 7 607 611 093.
    
    NOTE: If the speedometer stops working after the radio has been fitted, this pin has most likely been grounded by the radio using the pin for some function other than GALA. Detach this wire and see if the speedometer returns to normal. On MB and RR-engined cars, this signal also controls idle stabilisation and the automatic differential unlocking system
    
    
  • Pin 2 - mute control - grounded by external components to mute the radio, often used when a mobile telephone is fitted to the car.
    
    See the telephone handset installation instructions. On a 1985, 1986 or 1987 ur-quattro with a green digital dashboard, this pin should also be connected to pin 16 of the voice synthesiser/autocheck unit so that the radio can be muted when warning messages are issued.
    
    
  • Pin 3 - RFLS - Ruckfahrtlichtschalter - the reversing light switch.
    
    Satellite navigation systems use this signal, the GALA signal (pin 1 above) and an internal laser gyroscope for "dead reckoning" in the absence of satellite signals. +12v input to the radio with the ignition on and the car in reverse gear.
    
    
  • Pin 4 - permanent +12v input to the radio from the battery, already in the DIN radio harness.
    
    Note that VW and Audi normally installed radios in such a way that they operated with the ignition off - thus one wire in the standard DIN connector is a permanent +12v equivalent to pin 4 above. This is because of ecological concerns raised when the German forests started dying off in the late 1970s - people waiting in cars for friends to come out of their houses would idle the engine just to listen to the radio. Connecting the radio directly to the battery (usually via Fuse 4) eliminated the requirement for the ignition to be on. Some more modern radios have automatic power-off functions. Some radios reverse the functions of pin 4 and pin 7.
    
    
  • Pin 5 - automatic aerial - +12v output from the radio.
    
    Maximum 150mA, to drive an automatic or electronic aerial. From 1985 onwards this is a white wire in the radio harness - different colours were used on earlier cars; check the colour of the wire in the small single pole connector on the radio aerial. If present it MUST be connected, even if the aerial is not automatic. It also operates the buzzer that warns of the radio being on when the door is opened - see the note below.
    
    
  • Pin 6 - illumination - +12v input to the radio when the car's lights are on.
    
    In some radios this actually lights the display - in others it dims it, reverses the black-on-white aspect, or even changes the colour from green to orange. If the dashboard has a dimmer function, this pin should be connected to the dimmed part of the display. The wire to the cigarette lighter bulb - usually grey/blue - can be used.
    
    
  • Pin 7 - ignition - +12v input to the radio when the ignition is on.
    
    On ur-quattros with the combined LED voltmeter and oil temperature gauge, the black wire to pin 2 on that unit is a useful source of switched 12v. On earlier cars, the power feed to the differential lock lights should be used.
    
    
  • Pin 8 - chassis ground - already in the DIN radio harness, but usually black instead of Audi's normal brown.
    
    
• Connector B is for the loudspeakers. Which loudspeaker a particular pair of wires goes to can be identified using a small battery - preferably a mercury "button" cell or a discarded AA or AAA battery with very little charge left in it. The loudspeaker will click noticably. They only have a resistance of around 4 ohms, so 9v batteries must not be used. The wires are in obvious pairs - the one with the stripe is the "+" sense.
  
  
  • Pin 1 - Right rear speaker +
  • Pin 2 - Right rear speaker -
  • Pin 3 - Right front speaker +
  • Pin 4 - Right front speaker -
  • Pin 5 - Left front speaker +
  • Pin 6 - Left front speaker -
  • Pin 7 - Left rear speaker +
  • Pin 8 - Left rear speaker -
    
    

    On green digital dashboard ur-quattros, some of these wires must be passed through the voice synthesiser unit. If a separate amplifier is fitted, note that the voice synthesiser outputs at high volume. The test function (depress the computer reset button while switching on the ignition) can be used to adjust the amplifier's gain control. It may prove better to attach the mute (pin A2) and provide a separate small loudspeaker for the voice synthesiser output.

• Connector C is actually three separate connectors dovetailed together. It may not be present at all - sometimes, only parts of it are present. It usually comes attached to the device it supports:
  
  
  • C1 - external amplifier or equaliser
    • Pin 1 - Line out left rear
    • Pin 2 - Line out right rear
    • Pin 3 - Line out ground
    • Pin 4 - Line out front left
    • Pin 5 - Line out front right
    • Pin 4 - +12v switched - maximum 150mA
  • C2 - remote control
    • Pin 7 - RXD
    • Pin 8 - TXD
    • Pin 9 - Chassis ground
    • Pin 10 - +12v switched - maximum 150mA
    • Pin 11 - Remote control in
    • Pin 12 - Remote control ground
  • C3 - CD changer
    • Pin 13 - CDC data in (bus)
    • Pin 14 - CDC data out
    • Pin 15 - CDC +12v permanent
    • Pin 16 - CDC +12v switched - maximum 300mA (+A)
    • Pin 17 - CDC data ground (+U)
    • Pin 18 - CDC audio frequency ground
    • Pin 19 - CDC audio frequency left
    • Pin 20 - CDC audio frequency right
      
      
• Connector D is only present on satellite navigation systems - it is documented in the relevant manuals.

Halfords' adapter range is indeed excellent - each wire has its function printed on it as a useful confirmation that connection is correct. There are DIN to ISO adapters and ISO to DIN - if fitting a modern radio into an ur-quattro, the best strategy is to adapt the existing harness entirely to ISO and purchase the ISO to DIN adapters in case anyone wishes to replace the original radio. Leaving a short piece of wire attached to each loudspeaker plug will allow the plug to be crimped onto the leads of an ISO adapter so that a radio with DIN loudspeaker connections can be fitted.

Note that the original Blaupunkt SQR is now a collector's item - eithe retain it with the car for a future owner or sell it via eBay.

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