Fitting Audi B3 / B4 VDO gauges to mk2

Fitting Audi B3 / B4 VDO gauges (Volts, Oil Temp & Oil Press to Golf Mk2)
Wire colours on the VDO gauge harness are:
Blue / black - Switched 12V (terminal 15)
Brown: Earth (terminal 31)
Green / black - Oil temperature signal
Light blue / white - Oil pressure signal
Grey / blue - Illumination
Red / blue - cigarrette lighter feed (not needed)
Cut off the white plug, not required on a Golf.
Locate a switched 12V supply, and connect the blue / black wire.
Locate a good earth, and connect the brown wire.
The voltmeter is now operational, as are the oil pressure and temperature gauges, though the latter 2 need a signal
For the oil temperature gauge, extend the green / black wire, and locate THE SAME colour at the back of the fusebox. Connect the extended green / black wire.
Under the bonnet, locate THE SAME green / black wire - usually tucked away by the oil filter housing. Remove the zip tie if there is one.
On the oil filter housing, locate the blanking plug (usually a 5mm allen bolt). Remove this plug, and replace with the screw-in sensor. Connect the green / black wire to the sensor. The oil temperature gauge is now operational.
Now for the oil pressure gauge. Working inside the car, extend the blue / white wire, and locate a suitable bulkhead grommet. Pierce your chosen one, and run the wire through into the engine bay. Take care when routing, that it is not trapped, or likely to catch on any moving parts.
Remove your existing oil pressure switch from the oil filter, and replace with the 2 pin sender supplied.
Care is required here - the 2 terminals are different. One is marked with a blue paint mark. This one MUST be connected to the extended blue / white wire, fitted with a suitable female spade connector. The remaining terminal MUST be connected to the original connector, which operates the oil warning lamp and buzzer.
Back inside the car, locate the instrument illumination feed behind your dash - easiest way is to tap into the grey / blue feed for your heater panel illumination. Splice the grey / blue wire from your gauges to this feed, an extension may be required.
Now, switch on your sidelamps, gauges should illuminate.
Switch on the ignition - voltmeter should read at least battery voltage, and oil pressure and temperature gauges should JUST move up from their rest positions.
Start the engine, voltmeter should read approx. 14 volts with all consumables switched off. On a cold engine, oil pressure should be at least 4.5 - 5 bar at idle.
Oil temperature will rise slowly as the car is driven. If the car is driven hard, temperature could be anything between 70 and 90 degrees celsius. On a very hot day, with sustained high rpm, it could rise as high as 120 degrees. Ideally, you want to back off at this point, till the temperature drops.
NEVER let the oil hit 130 degrees!! If it regularly reaches the 120 degree mark, you may want to invest in an oil cooler.
It is normal for the oil pressure to drop as temperature rises, at idle with the oil at 90 degrees, a pressure reading of 1.3 - 2 bar isn't uncommon. It should rise to 4.5 bar minimum above 2,500rpm on a healthy engine, 5 is ideal. An engine with a lot of hard miles under it's belt may only rise to 4 bar above 2,500rpm, but no cause for alarm.
This is based on the VDO coming with the wiring harness, mine are ALWAYS supplied with harness and sensors.
This is for Golf 2 fitting, Golf 1 & 3 similar, though location of oil pressure / oil temperature may vary, depending on engine type. Golf 1 & 3 may NOT have the signal wire for oil temp (green with black trace) in place.
If car is a GTI with OE MFA fitted, it WILL have the oil temperature signal wire in place, but do NOT use the sensor as a common for the MFA oil temperature, as well as the VDO gauge. It will cause the MFA to read not only oil temperature, but also the internal resistance of the VDO gauge. (Analogue gauges have a higher impedance).
In such cases, either find another blank on the oil filter housing, or on the cylinder head for the extra sensor to provide the signal to the VDO. Or, alternatively, use a splitter available from any hydraulic coupling centre with the appropriate thread to fit the original MFA location, with the 2 internal threads suitable for the OE VDO and MFA sensors.