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Starter motor (repair)
| Is finding the defect perhaps more expensive than exchanging the part? |
Before searching for a possible defect or starting to repair a starter, at least in the case of the motor car, one should find out the price of an exchange unit. Perhaps it would make any repair work on the starter an
economical total loss. The customer will not want to accept the price of the starter and also the hourly rate charged for repair attempts.
| Voltage drop and battery performance? |
Wait a minute, perhaps the defect is not in the starter itself. Has e.g., the voltage drop of the battery, when turning the ignition key been tested? Or the current supply to the starter? Should it be too low, the error may be
that the contact resistance is too high, e.g., in the connecting cable or it's terminals. In this case, please check the entire earth cable, right up to the battery.
| Diesel compact class: Starter current -> 400 - 500 A |
Finally, there is still the peculiar error, that when trying to start, nothing happens at all. If the solenoid is ok, then obviously the contact resistance in the ignition switch (if the car still has one) is too high. Installing a shunt-
relay between the ignition switch and the solenoid often saves you buying and installing a new ignition switch.
| The condition of the flywheel teeth? |
This is still not enough reason to simply replace the starter. After switching off the ignition, the combustion engine has the strange habit of always coming to a stop in one or two typical positions. When starting again,
the starter must mesh in exactly at this point. This is why the teeth wear out particularly here. What we do of course, is to turn the flywheel one complete rotation, checking it thoroughly through the starter opening.
| Always measure the short circuit current in less than 2 seconds. Unless the manufacturer states
otherwise, the max. allowed voltage drop should be approx. 0,5 V. |
The test bench (see above picture) is designed for the correct checking of the starter, also, and particularly, after the repairs have been done. Here, the starter can be mounted and brought to a halt by a drum brake.
Furthermore, during the idling check, without any strain, the RPMs can be measured. Indeed, one has to have a lot of repair inquiries, before the purchase of this type of test bench is worthwhile, particularly as one can
also carry out, e.g., the short circuit testing when the starter is still mounted.
| A lot can be found out by listening and measuring, without dismantling the starter. |
Finally, the particular importance of acoustic checking must be emphasized once more. Due to the fact that the starter is not the quietest component anyway, defects can be particularly well recognised by the noises
they make. This can mostly be done by the driver, he/she will notice if the normal starter noises change. One can hear whether the meshing was successful or not, also the difficulty of finding the correct point to mesh
in, when the teeth are damaged, or the meshing-in/out takes too long. In this case, the gearing on the flywheel may also be damaged, which makes the whole business of repairing a lot more expensive. This is why,
one should take suitable measures as soon as one hears any strange noises.
| The starter won't turn, the carbon-brushes are not making contact. |
The starter must not necessarily always be completely replaced. It's quite possible that only the solenoid is faulty. This can be recognised, when attempting to start, and no sound can be heard, not even a clicking
noise. That would be heard if the starter itself was the problem. If the problem was in the starter itself, one would at least hear the sound of the solenoid. The clicking sound that you hear is, so to speak, the deciding
factor, whether the starter-motor or only the solenoid is damaged. Of course, sufficient battery voltage must be available. However, the clicking sound may still be heard if the battery is weak. 09/13
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