BMW AG Motorcycle (K1100LT, K1100RS). Manual - part 13

12.21

Checking starter relay

•

Connect terminal 86 to positive battery terminal, 
terminal 85 to earth (ground).

L

 Note:

The relay is defective if no switching noise can be 
heard.
Check resistance if clear switching noise can be 
heard.

Checking starter relay with ohmmeter 

•

Connect positive lead from measuring instru-
ment to terminal 30, negative lead to terminal 87.

L

 Note:

Ω

 value indicated means relay is defective.

LT120200

+

86
85

-

LT120210

30

OL

87

-

+

12.22

Troubleshooting

Troubleshooting on alternator

Alternator makes noises.
Do carbon brushes whistle?

yes

Rework slip rings/replace carbon brushes. 

Battery produces excessive gas (vapour)

no

Check contact between regulator/alternator 
and between alternator/diode carrier.
Is contact poor?

yes

Repair cable connections.

no

Check regulator.
Is regulator defective?

yes

Renew regulator.

no

Check battery.
Is battery defective?

yes

Renew battery.

12.23

Indicator lamp lights at only half brightness 
intensity when engine running.

no

Check contacts of cable connections. 
Do cable connections have poor contact.

yes

Repair cable connections/plug contacts. 

no

Check regulator.
Is regulator defective?

yes

Renew regulator.

no

Check carbon brushes.
Are carbon brushes defective?

yes

Renew carbon brushes. 

no

Check rectifier.
Is rectifier diode defective/does rectifier diode 
have short to earth (ground)?

yes

Renew diode carrier.

no

Check alternator.
Does stator have short to earth (ground)?

yes

Renew stator. 

no

Check rotor.
Does rotor partly have short to earth (ground)?

yes

Renew rotor.

12.24

Indicator lamp lights at half or full brightness 
with engine running. 

no

Check regulator.
Is regulator defective?

yes

Renew regulator. 

no

Check supply line. 
Does supply line have break/short circuit?

yes

Repair break; 
renew cable/connection elements. 

no

Check carbon brushes.
Are carbon brushes defective?

yes

Renew carbon brushes. 

no

Check rotor winding.
Is rotor winding defective?

yes

Replace rotor. 

no

Check exiter current circuit.
Is exiter current circuit broken?

yes

Repair break;
renew cable/connection elements.

no

Check diode/diode carrier.
Is diode/diode carrier defective?

yes

Replace diode/diode carrier.

no

Check cable D +/61.
Has cable short to ground?

yes

Repair short-circuit; 
if necessary renew cable.

12.25

Indicator lamp does not light when engine is 
stationary and ignition switched on. 

no

Check indicator lamp.
Is lamp defective?

yes

Replace indicator lamp.

no

Check battery.
Is battery discharged/defective?

yes

Charge/renew battery.

no

Check alternator.
Has generator short at positive diode?

yes

Immediately disconnect charge line (discharge 
when stationary). Repair alternator.

no

Check cable.
Is cable loose/damaged?

yes

Secure connections/renew cable. 

no

Check regulator.
Is regulator defective?

yes

Renew regulator.

no

Check carbon brushes.
Are carbon brushes worn?

yes

Renew carbon brushes.

no

Check rotor winding.
Do slip rings have oxidation layer?

yes

Repair alternator.

no

Check rotor winding.
Is rotor winding broken?

yes

Renew rotor.

12.26

Troubleshooting on starter

Starter does not turn when start switch is 
operated.

no

Switch on light. Does light operate?

no

Check battery.
Is battery discharged, defective?

yes

Charge or renew battery.

no

Check power circuit.
Does power circuit have a break?

yes

Repair break.

12.27

Starter does not turn when start switch is 
operated.

no

Switch on light. Does light operate?

yes

Connect jumper at connection between termi-
nal 50 and 30. Does starter turn?

yes

Check ignition switch and supply line.
Is ignition switch defective?

yes

no

Replace ignition switch.

yes

Is there a break in supply line?

yes

Repair break. 

no

Check carbon brushes.
Are carbon brushes too short?

yes

Replace carbon brushes. 

no

Are carbon brushes jammed?

yes

Release carbon brushes.

no

Is spring pressure acting on carbon brushes 
too low?

yes

Replace compression spring.

12.28

Starter turns too slowly, does not crank en-
gine.

no

Check battery voltage.
Is battery voltage too low?

yes

Charge battery, replace if necessary.

no

Check battery terminals.
Are terminals loose or oxidised?

yes

Clean poles and terminals, firmly tighten.

no

Check connections.
Are connections loose?

yes

Secure connections.

no

Check collector.
Is collector dirty?

yes

Clean collector.

no

Check armature winding. 
Is armature winding defective?

yes

Repair starter.

Starter turns at high speed.
Engine stops or turns only sporadically.

no

Check drive pinion. Is drive pinion defective?
Is shift lever broken?

yes

Repair starter.

Drive pinion does not engage.
Starter turns idle at high speed.

no

Check drive pinion.
Is drive pinion excessively dirty?

yes

Repair starter.