Bosch type 154740 Carbon brushes Fitting Information
Personal safety at all times
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.
Checking the motor carbon brushes
Down to the actual brush changing! All Bosch washing machines that use these Bosch 154740 carbon brushes are not the same, nor do they even use the same Bosch motor. In fact the only thing that they have in common is that they all use these carbon brushes part number 154740.
First of all, 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 on the motor from the socket on the machine. On other models you will need more access than described above to actually access the motor fixing bolts. 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 touch and rub on and actually make contact with the armature. When the surface of the commutator appears to be damaged because of the worn out carbon brushes, you are looking to see if any segments of copper are raised and out of line with the rest. If this is the case it is absolutely final and requires a replacement motor!
Testing the 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 check ensures that the meter is actually working and does not have a flat battery or some other fault. Next, touch one probe on to the frame of the motor and the other probe on to the surface of the commutator. Should 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).
No Reading is Good
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 carbon 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 come this far, remove the Bosch 154740 carbon brushes retaining tags from the end of each brush holder. Withdraw the worn out carbon 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 anywhere on the motor. Do this using a dry cloth or paint brush or an airline if you have access to one.
Fitting the replacement carbon brushes
Having done all of this, you are now ready to fit the replacement Bosch 154740 carbon brushes. Gently slide the new carbon brushes into their respective brush holders. Do they slide in all the way freely without jamming? If so, fine, replace both carbon brushes the same way. If the brushes do not slide freely all the way in, do not use force. Instead withdraw the brush or brushes before they get jammed completely. What has happened here is that the metal brush holders have distorted, maybe only very slightly. This is due to the continuous heating and cooling of the motor throughout its working life.
What you need to do now is to use a file or a Stanley knife or some other scraper. Gently scrape away at each corner of each carbon brush. Do this to each corner in turn until the carbon brush slides into the holder freely. If this does not work try scraping one edge of the brush. Do this just until it slides freely into the holder. Both carbon brushes must be free to slide in and out of their respective holders before carrying on any further.
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.
Cleaning the commutator
Correct any excessive clicking of the new brushes by cleaning up the commutator. Do this using a comm stick. Do not use emery cloth or sand paper as these can cause serious damage to the motor. Take the motor to a reputable trades person should you not have access to a comm stick.
When you have done all of this, then it is time to replace the motor into the machine. Use the reverse procedure to the removal. Once the motor is back in its location in the machine, tighten the securing bolts. Apply gentle tension to the drum drive belt. Do not over tension the belt! After replacing the machine covers, you should now be ready to test the machine. Now to find out if your repair has been successful!.
Hope this helps, and good luck with your repair project!