Component Tests and General Diagnostics

H1 Items to check:

In-Car Checks:

- battery is at least 3/4 charged
- battery terminals are secure and not corroded
- ground straps between: battery - body and engine are secure and not corroded
- starter motor cables are correctly connected

H2 Seized starter motor





Connect meters as illustrated. Engage top gear and apply hand and foot brakes. Turn starter motor (max. 5 sec) and check meters. If reading is not same as the specified value (see H6), the recorded current strength must be recalculated according to H7. Remove starter motor for inspection if test values are different from manufacturers specifications.

H3 Checking control solenoid

Fig. 1 Checking Control Solenoid:

Connect battery as illustrated. No other leads may be connected. When circuit is completed, the drive should slide Out of solenoid and remain so as long as current is switched on. Replace solenoid if defective.

Testing Starter Motor On A Test Bench
H4 Connecting - up





Clean and dry starter motor and secure it firmly to test bench. Connect test meters as shown.

Note: The test bench must be equipped with a shunt of at least 900A .

H5 Starter motor connectings





B+30 = from battery (+)
50 = from starter motor terminal 50
16 = to ballast resistor, ignition coil
M = to starter motor field coil

H6 Test values

Specified Values:

The specified current and voltages given in the second image should be obtained when testing a starter motor. If voltage is not the same as test values the current can be converted. Values which differ from manufacturers specifications may be caused by the differing capacities of the test bench battery and standard battery.

H7 Conversion to another voltage





Bosch 0 001 311 1..
I = Manufacturer's specification (410-490 A according to test H6 locked starter motor).
Ix = Measured current consumption in test bench.
U = Manufacturer's specification (6.5 V according to test H6).
Ux = Measured voltage in test bench.

H8 Example:





Locked starter motor
I = Ix . U / Ux
Measured values: Ix = 350 A
Ux = 5 V

Manufacturer's specifications:
I = 410 - 490 A
U = 6.5V

Calculate I, and compare it to the manufacturer's specifications (I).
I = Ix . U / Ux
I = 350 x 6.5 / 5
I = 2275 / 5
I = 455 A

The calculated value of 455 A lies within the manufacturer's specifications (i.e. 410-490 A).

The measured value 350 A has been converted to 455 A and is thereby a fully acceptable result.