Electrical Fault Finding

Resolving electrical faults for some is easy and others daunting but following simple procedures can make it easy. First learn to use a multimeter to measure voltages between a wire and earth and secondly measure resistance between two ends of a wire or two pins on a component.

Thirdly identify any intelligent components such as ECU's or Dash and understand that there may be complex data communications between intelligent components rather than simple on or off voltages.

The final element is to learn the BMW color code system. It is common to all the vehicles with some small variations.

BMW Color Codes

The full color code lists are in the index of the wiring diagrams, these are the main colors with explanations of their normal usage. The color code system can break down at the final socket to a component, where generic parts are sourced. An example is the ABS sensor wiring. The 3 primary wiring colors are :

Rt - Red - Normally unswitched +12v
Br - Brown - Normally -12v (earth)
Gn - Green - Switched +12v
Red with a strip indicates unswitched power for a specific circuit
Brown with a stripe indicates a return wire from a component to earth
Green with a stripe indicates power to a specific circuit

Examples of the color stripe system are below

Rt/Sw - Red/White - Fused Power to Components
Rt/Ge - Red/Yellow - Power to Load Relief Relay
Gn/Bk - Green/Black - Power from Load Relief Relay

Br/Sw - Brown/Black - Sidestand diode return wires
Br/Or - Brown/Orange - Earth return from Engine Parts
Gn/Vi - Green/Violet - Power to Horn from Switch

BMW Wiring Diagrams
The BMW wiring diagrams can be difficult to follow at times as circuits are split across multiple diagrams and there are errors in diagrams. The BMS/Dash/ABS are the main area single page diagrams are useful to understanding the operation of the systems. The single page diagrams here are intended to simplify fault finding. The G Series 10-14 diagram includes the Sertao. These are the first revision so may have errors. Let us know if you find any errors.

BMS / Dash / ABS Diagrams F650GS 00-04 F650GS 05-07 G650GS 08-09 G650GS 10-12 G650GS 13-16

2013+ BMS-E equipped models have fuel pump and fan relays mounted under the seat near the fuse box.

Alternator Stator, Starter Clutch and Flywheel Parts

There are differences between F Series and G Series parts, the Part Nos are in the pdf. Generator Parts

It appears the G Series starter clutch has been changed with most other parts remaining the same.

Dash Lamps and Front Parking Lamp
The dash lamps are the same on all 650GS models 2000 to 2009
All except Indicators/Speedo/Tacho are 1.2w. These 4 are 3 watts.
BMW list the dash lamps as type w5/1.2w. (also called BS286 or T5)
The front park lamp is T10 (type 194 ?). Base may be too wide.
Information on LED globes is in the pdf LED Globe Info

The majority of the dash lamps operate independently of the dash electronics.

The method of operation of the dash lamps on the all the 650GS from 2000 to 2009 is below.

The 00-09 Dash info pdf on Electronic Repairs page has more information on Fuel & ABS lamps.

ABS - Operates via circuitry in Dash
Fuel - Via circuit in Dash with delay and latch
High Beam - Power on White wire from High Beam
Indicators - Operates across the L/R indicator wires

Coolant - Earth on Violet wire from the BMS-C
Neutral - Earth on Br/Sw wire from neutral switch
Oil P - Earth on Br/Ws wire from pressure switch
Note - See Mods/LED for LED flasher modification.


Headlight and Globe Tests
To test a faulty headlight system start at the headlight socket
Disconnect the H4 socket to the headlight and then test as follows
Test for +12v at the Headlight socket with the ignition on
Test for resistance on the globe, Yellow to Earth, White to Earth.
Note - H4 (EU) and 9003/HB2 (US) are equivalent
Indicator Relay Tests

Wire 2 Flasher sockets together, connect to BMW Relay O/P & +12v to I/P.

Tail light and Globe Tests
The tail light globe can make poor contact in the globe holder
TailLight - Test for +12v on grey/black wire with the ignition on park
BrakeLight - Test for +12v on green/red wire with the brakes on
Test for resistance on the globe, Pin1 to Earth, Pin2 to Earth.


Battery Parasitic Drain
The term "Battery Parasitic Drain" is unfortunately commonly used to describe the normal drain on the battery when the ignition is off. In professional circles it is used to describe abnormal battery drain from a fault in components.

The Dash and BMS-C have connections for both switched and unswitched power. When the ignition is turned off there will be approximately 70 milliamps current drain, then after approx 5 seconds both components should go into sleep mode. When in sleep mode the total current drain is 1 to 2 milliamps.

There can be a number of causes for abnormal battery drain in a modern machine, the main faults are listed below.

ECU's - Dash and BMS-C may not be going into sleep mode. There is no history of this on the GS.

Harness Chafing - The wiring harness chafing is known to cause parasitic drain. See Wiring Repairs.

Starter Solenoid - "Feathering" or very fine metallic fragments can build up on the solenoid contacts.

Relays - As per the starter solenoid "feathering" can build up on relay contacts. Replace the relays.

The full list of components with unswitched power is :-
Ignition Switch, Solenoid, Voltage Regulator, BMS-C, Motronic Relay, Instrument Panel, ABS, and Load Relief Relay

The safe basic procedure for finding the fault is to put a multimeter in the earth lead circuit on the battery using the 0-10 Amp connections and disconnect components one by one to locate the faulty component.

The multimeter will initially read 0.07 then drop to 0.00 if there is no abnormal drain. The multimeter can be used in 200ma range to get better readings but the 10amp range is safer for those less experienced with multimeters.

Removing Fuse 1 isolates the BMS-C and Motronic Relay.
Removing Fuse 2 isolates the Load Relief Relay.
To isolate ABS and BMS-C disconnect sockets as +12v is not fused.
Removing Fuse 2 isolates the Dash and Flasher Relay.