Bosch exxcel 7 water hammer

[gNick]

I have a Bosch Exxcel 7 washer that has started causing a water hammer on the final spin cycle. This started after I changed the brushes so may be because something got disturbed when the washer was lying on its front.

 Having a good investigate with the cover off, the solenoid on the water inlet valve is being operated in about 1sec pulses which is causing the water hammer, it's also leaving water in the conditioner part of the detergent drawer.

 So something is momentarily switching the inlet valve solenoids. Does anyone have an idea of where I should look next? Getting the Bosch engineer out is something I'd rather not have to do, given that it's well out of warranty!

 Nick

[Whitegoodshelp (Andy)]

Strange. A shuddering water valve could be caused by a poor electrical connection but the water valve shouldn't be activated on spin. One possible explanation could be if water has got in somewhere when it was laid down. It's ok to lay a washing machine down but you need to ensure all the water has drained out first. It's possible the fault could disappear after several days although if the water dries up or runs off but that's a bit of a long shot. Does the motor spark badly when this happens?

[gNick]

I suspect that it isn't water getting in as it didn't happen straight away.

 There wasn't noticeable sparking and it was only happening on the final spin cycle which is a bit odd. There is a lot of carbon dust everywhere, something tell me that cheap brushes are cheap for a reason, and the motor is noisier than it was, especially in reverse. Do you have any recommendations for brushes?

 Oddly I laid it down again, to check the motor wiring and gave the connectors into the controller a bit of a wiggle and on the next try the problem had stopped. It will have a proper run tomorrow to see if the problem comes back. It must be something to do with the controller, maybe a relay controlling the valve solenoid?

 I might just buy a water hammer arrestor anyway, just in case!

[Whitegoodshelp (Andy)]

You need to use the genuine carbon brushes. The cheap brushes usually work ok but they can be too soft and wear out quickly. They can also coat the inside of the motor in carbon dust which can short it out.  If the motor is sparking excessively it's no good, it could be that the armature is worn.

[Whitegoodshelp (Andy)]

Water hammer should only occur when a washing machine energises the water valve and when the valve shuts off it creates a shock wave that causes loose plumbing pipework to knock. It is normally stopped by finding the loose pipework and securing it properly. Also, it only happens with high water pressure so turning down the mains water pressure in the house usually stops it too. 

Having said that the water valve should not be energised at all on the spin cycle. So if these faults are caused by the water valve erroneously activating, possibly repeated times that's a weird fault. Is the motor sparking excessively? Even so water hammer should only happen if you also have high water pressure and loose pipes. Search how to stop water hammer on Google if you haven't already. But I agree that the washing machine shouldn't be causing it on spin. Can you observe that the water valve is being activated when it does it? Can you feel vibrations on the water hose connected to the machine?

[Adrianmark]

Was this issue ever resolved? I have exactly the same problem with my Hotpoint HE7L252 Experience after bizarrely, the same as gNick, having changed the brushes in the motor. The solenoid on the inlet valve is definitely being activated during the last spin cycle, for around a second each time, quite frequently, as I can feel the pipe pulsing! I have done many repairs to washing machines over the years but have never come across anything as odd as this!