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Fitting 154740 carbon brushes
First of all! If you are going to examine your Bosch motor brushes, of utmost importance! Disconnect the appliance from the mains electricity supply! Do this by removing the plug from the supply socket or by switching off at the main consumer unit. This can usually be accomplished by switching a single breaker, which, if it is an up to date RCD (residual current device) hopefully it will have been labeled Kitchen Sockets, Utility Room Sockets, House Sockets, Garage Sockets, you get the idea, where ever your appliance is situated. It may also be a wise move to ask anyone who is working at a computer that is mains powered to back up their work before switching off.
Down to the actual brush changing! All Bosch washing machines that use these 154740 brushes are not the same, nor do they use the same Bosch motor, in fact the only thing they have in common are the brushes part number 154740. Remove the rear panel from the machine, on some models this will be enough for you to be able to remove the single fixing bolt, slacken the tensioner bolt and remove the motor, carefully disconnecting the plug from the socket on the motor. On other models you will need more access than described above to actually access the motor fixing bolts and the best way to do this is to lay the machine down on its side with the soap dispenser to the top away from the floor, this will give full access to the motor fixing bolts. Having removed the motor, examine it for any physical signs of damage, particularly the surface of the commutator where the brushes rub and make contact with the armature. If this looks to be damaged in any way, what you are looking for is to see if any segments of copper are raised and out of line with the rest, if this is the case it is usually fatal and requires a replacement motor!
To test this requires the use of a megger or some other voltage producing tester, but a simple test can be carried out with a basic resistance measuring meter, such as a multimeter which may be purchased at a very reasonable price. Before doing a test, switch on the meter and set it to the lowest Ohms range, touch the two test probes together and the screen should indicate zero resistance, this is just to ensure that the meter is actually working and does not have a flat battery or some other fault, now, touch one probe on to the frame of the motor and the other probe on to the surface of the commutator, if you see any reading at all there is a problem and this needs either testing with the proper equipment or the motor needs to be replaced as there should be no electrical connection at all between the commutator (live) and the frame of the motor (earth). If you do not see a reading on the meter screen, good, but this is not necessarily the end as this is only a crude test and is an indicator only that it may be worthwhile continuing with fitting the replacement brushes. Another quick test you can carry out with a test meter is, touch one probe on to one of the brass brush holders and the other probe on to each connector in turn in the motor socket until you see the meter read zero ohms once more, then repeat this from the other brush holder, this is telling you that the temperature fuse embedded in the motor windings is OK and has not blown due to the motor overheating. Having got this far, remove the brush retaining tags from the end of each brush holder and withdraw the worn out brushes which may be intact but may also have broken up and disintegrated. Once removed, it is good practice to clean off all of the excess carbon dust from any where on the motor with a dry cloth or an airline if you have access to one.
Having done all of this, you are now ready to fit the replacement carbons. Gently slide the new carbon into the brush holder, does it slide in all the way freely without jamming? if it does, fine, replace the second brush the same way, if the brush does not slide in freely all the way do not force the brush in, instead withdraw the brush before it jams, what has happened is that the metal brush holders have distorted slightly due to the continuous heating and cooling of the motor throughout its working life. What you need to do now , is, using a file or a Stanley knife or some other scraper, scrape away gently at the corners of each brush in turn until it slides in to the holder freely, if this does not work try scraping one edge of the brush again just until it slides freely into the holder. Having accomplished this, push the spring down the brush holder and replace the tag to hold it in place, repeat this for the second brush. Now, rotate the motor shaft with your hand and ensure that it is not scratching and clicking as it rotates. If it is clicking excessively, you may need to clean up the commutator, or get it cleaned, this should be done with a comm stick and not with emery cloth or sand paper as these can cause serious damage the motor. Once this has all been accomplished, then it is time to replace the motor into the machine, using the reverse procedure to the removal. Once the motor is back in its location in the machine, tighten the securing bolts and apply gentle tension to the belt. Do not over tension the belt! After replacing the machine covers, you should now be ready to test the machine and find out if your repair is a success!.
Hope this helps, and good luck with your repair project!