Hotpoint Wm31 Spin Failure
The brushes have been replaced (correctly) with new Hotpoint original parts but there is still no rotation. Can you tell me if there are some basic electrical tests which can determine whether the motor is likely to be faulty or the speed control module has failed ? For example, using a multimeter, what voltage should appear on the brushes ? Or what voltage should be on each of the connector pins ? (I am an electrical engineer....but not in domestic appliances).
Solution Summary
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This thread was marked as solved. Here's a summary of the problem and the fix, generated from the discussion below.
Hotpoint WM31 motor not rotating after brush replacement
- The problem
- After fitting new genuine Hotpoint carbon brushes, the washing machine still had no drum rotation/spin. The user wanted to determine whether the fault was in the motor or the speed control module.
- Likely cause
- Open-circuit TOC in the motor was identified by continuity checks. The discussion suggests this was probably caused by arcing/flashing when the previous brushes failed, although possible armature damage was also noted and not ruled out.
- What fixed it
- Recommended diagnosis was with the machine unplugged, using continuity tests on the motor pins, field coil, armature and brush wiring rather than live voltage checks. The original poster confirmed the motor TOC was open circuit. Advice was to source and replace the correct TOC for motor 904/1158/04 (HPT1601978), not bypass it, and inspect the armature carefully first because a faulty armature can also cause TOC failure. Exact completed repair was not confirmed in the thread.
- Checks to try
- Continuity test on motor connector pins to identify armature and field coil readings
- Continuity test across the armature pins
- Continuity test from black brush wire to an armature pin
- Continuity test from yellow brush wire to the other armature pin
- Inspection of brushes for charring or sticking in the holders
- Inspection of armature copper segments for looseness or flash marks
- Insulation-to-earth test of the armature with a proper insulation meter
- Parts or tools mentioned
- Hotpoint original carbon brushes
- TOC for motor 904/1158/04 (HPT1601978)
- Continuity test meter
- Insulation meter
Safety: Do not carry out live voltage testing on the washing machine. Do not bypass the TOC. Further diagnosis should be carried out by a suitably qualified appliance engineer.
3 Answers
I would advise against trying to get any voltage readings from a washing machine. It's unecessarily dangerous. There are no published readings because all fault diagnosis like this should be done with a continuity test meter and with the washing machine unplugged.
Disconnect the washing machine from the electricity supply and unplug the motor.
With the test meter on continuity test (to check resistance) do the following checks -
If your motor has 6 pins, then the 1st two pins (from the left as you look at it from the front of the machine) are the armature. The next 2 pins are the field coil. The last two pins are the tacho coil
If your motor has 7 pins. Then the first pin on the left is an extra field coil pin and the rest are the same as the 6 pin motor i.e. the next two are the armature and the following two are also the field coil. The final two are also the tacho coil.
Forget about the tacho coil (the two over on the right)
You should get a reading on the field coil tags so if you have a six pin motor test the two middle pins and you should get a reading between them. If you have 7 pins, you should get a reading on the 1st pin and the 4th pin. The 1st pin and the fifth pin and also between the fourth and fifth pins
This leaves the armature. On the six pin motor its the first 2 pins. See if there is a reading between them. On the 7 pin motor it's pins 2 and 3 (from the left)
If there is no reading (open circuit) here then it means the brushes have a fault. However, it is possible that a TOC inside the motor has also gone.
To test this -
Pull off the black wire from the left hand carbon brush and test for continuity between the wire and one of the armature pins on the motor
Then pull of the yellow wire (from the right carbon brush) and test continuity down it to the other armature pin on the motor. Hopefully you will get a reading on them both. If not, then the TOC has blown
If you have an open circuit across the armature pins, but you do have continuity between the black wire and an armature pin, and the yellow wire and an armature pin, then the open circuit is likely to be caused by one or both of the brushes not making contact with the armature. Remove them and check they aren't charred - or if newly fitted check they don't stick inside the holders when pressed all the way in (due to the small locking tab not being prized fully out 90 degrees)
Hotpoint and Creda carbon brushes diagnostics & fitting
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This is all great stuff . I have been able to determine that my TOC is open circuit......probably caused by the arcing when the brushes failed (?). All I need to do now is source the correct TOC for a 904/1158/04 (HPT1601978) motor. If I can't do this locally then I'll be back ! Many Thanks.
This part is not made available by Hotpoint. They would only supply the full motor. It is available by a third party manufacturer though and I can send you one if you can't find one. Do not by-pass it.
If the TOC has gone, there is also a possibility that the armature is no good. I've even had the odd case where I could see nothing wrong with the armature, yet it blew the TOC when replaced. Having said that I have replaced many of these TOC's which had only blown because of the carbon brushes flashing and from arcing badly.
So, although there is a risk this could be in vain, the odds are more in your favour that it may pay off. Before fitting a TOC you need to carefully inspect the armature to make sure the copper segments are all OK (none loose or showing flash marks) You should also really test the armature's insulation to earth with a proper meter (one that tests the insulation with 500 volts)
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