This may help especially those of us, which are not that good in electrics/electronics as a DIYer and need some guidance how to do a simple DIY test of electric/electronic components in our car.
Simple instructions how to test relays http://www.wikihow.com/Test-a-Relay
All you really need to do this is a multimeter set on resistance, however, a 12 volt car battery could be useful. If a car battery isn't available, you can manually close the coil in the relay.
https://www.youtube.com/watch?v=_gIZ0weS7iU
How to Test a 3, 4 or 5 Pin Relay - With or Without a Diagram https://www.youtube.com/watch?v=IpRWcNoLdwQ&ebc=ANyPxKpdYVRa8zgsv3OwLzAfVdW0E-YWV4EYfI-EBenLCu4DO2FCjWhqZGlE4KNdEyHB9BUJZg6mkHzyOq17cztkEWiVy-XMaQ
What you need is a electronic contact cleaner and contact enhancer like DeoxIT or Stabilant 22A which BMW is using. Not similar to flushing type contact cleaners, DeoxIT or Stabilant, Wurth and some others dissolve oxidation on metal surfaces. This is especially important on older equipment and equipment exposed to severe environments (humidity, salt, and other contaminants). Dissolving oxidation lowers contact resistance, thereby increasing conductivity even more.
Stabilat 22A is recommended by BMW
Stabilant 22A Electrical Contact Enhancer Model: All BMW
Complaint:
Connectors which carry low current are more likely to form deposits which affect the resistance of the circuit through the plug connector. Depending upon the particular circuit these deposits can cause malfunctions and consequently activate warning lamps and check control indicators.
Remedy:
Part replacement can temporarily stop the problem.
If the connector is the problem then without disconnecting the connector measure the resistance of the circuit running through the connector to make sure the connector has a high resistance. A good resistor will have close to 0 ohms resistance.
Visually examine the male and female terminals in the connector housing by removing them. Look at the integrity of the wire crimps, and in some male terminals the integrity of the weld of the male pin to the terminal. Then reinstall.
With a zero residue electrical contact cleaner liberally spray the male and female connectors, and allow the air to dry.
Apply Stabilant 22A to both male and female terminals so they are saturated, and reconnect the connectors while they are still wet. When the Stabilant 22A dries it will leave a thin coating of polymer film which is conductive between mating surfaces, and is non-conductive between adjacent pins. It can also prevent the formation of more harmful deposits.
[PDF] Understanding European DIN Wiring Diagrams http://www.thesamba.com/vw/arc…r_Magazine_April_2003.pdf download it
