Bosch SGS6612GB/12 main circulation pump not running

[paltibine]

Old Bosch SGS6612GB/12 dishwasher, when started up it pumps out, fills the manifold, empties the manifold into the machine and then just sits there. There are a few clicks after a few minutes but no circulation and dishes are all dry.
I popped both sides off and can flick the pump round with a stick in both directions and it feels the same (very little resistance to being turned) when it’s switched off or when I would expect the pump to be running.
There are 3 wires to the pump (plus the earth), a white one on the LHS, a grey one on the RHS and another white one going to a black thing in the centre. Both the white wires seem to be at 240V both when I would expect the pump to be running and when I wouldn’t.

While the connectors look like normal spade terminals they don’t seem to want to come off so I guess there is some sort of clip which I haven’t figured out yet.

If it was a faulty pump wouldn’t I see the voltage changing on the terminals?

I’d appreciate any suggestions what to try next….
Thanks!

[electrofix]

correct you would see voltages on the terminal if pump was open circuit which would be rare

i would check the wiring harness at the bottom of the door where it bends

Dave

[paltibine]

Thanks Dave! I will check later and report back.
Do you know which of the 3 wires should have mains on them when it is running?

[electrofix]

paltibine wrote:Thanks Dave! I will check later and report back.
Do you know which of the 3 wires should have mains on them when it is running?

neither do I but if your getting no lives at all you know it cant be the motor

Dave

[paltibine]

Dave, I found 2 of the wires live but it didn’t seem to change between when I would expect it to run and when I wouldn’t expect it to.

“There are 3 wires to the pump (plus the earth), a white one on the LHS, a grey one on the RHS and another white one going to a black thing in the center. Both the white wires seem to be at 240V both when I would expect the pump to be running and when I wouldn’t.”

[electrofix]

that means your missing a neutral and it could be neutral switched so still check wiring

Dave

[paltibine]

So there are 4 terminals on the top of the motor marked 3 2 4 1 reading from the front of the machine to the back when looking at the right hand side of the machine. Terminals 3 & 2 seem to be connected together. Terminals 2 & 4 (the middle ones) are both connected to a small black box with only one terminal coming out. The terminal on the black box is connected to a white wire that comes from the main on / off switch and appears to be a permanent live connection. Terminal 3 (the front one) is another white wire that comes from the rear of the machine.
If I start up the machine with all the 3 wires disconnected it pumps out but doesn’t fill. If I connect the 2 white wires to their correct terminals then it pumps out, fills the manifold and then empties it into the machine ready to start washing.
The grey wire connected to terminal 1 doesn’t seem to have any voltage on it and doesn’t seem to make any difference if it’s connected or not. I have checked the voltage on it both when pumping out and when I would expect that main pump to be running. No volts under either circumstances.
Are these useful clues?

There are also a red and black wire going to a capacitor(?) at the side of the motor.
I’m a bit stuck now as I don’t really know if that implies it’s a faulty motor or the motor isn’t being switched on?

[electrofix]

the wire will come off the motor and go to the terminal blocks at the rear right. from there it may change colour and go through and into the door and connect to the timer. we need to know that wire is intact

Dave

[paltibine]

I’ve finally traced the wire all the way back to the control panel and the wire itself is fine. I can buzz the spade connector that connects to the motor terminal right onto the control board.
Does that mean it’s the control board or the motor?
I had a look at the control board and the device that is connected to that pin and it looks perfect.
Is there any way to test the motor? What voltage would it need that terminal to be connected to to make it turn?

[electrofix]

its a 240 v motor

i would measure the wire that comes down from the timer

put one meter lead on earth then measure voltage on the wire both when you switch on and as its running a programme

Dave

[paltibine]

Thanks Dave, I’ve done that. That wire always seems to be 0V.
Given that the other connection to the pump is always at 240V shouldn’t that make the pump run?
But it seems to be 0V all the time, when I first turn the machine on and when I would expect that motor to be running?

[electrofix]

should make it run

never had a motor coil fail but theres always a first time

do you get any resistance readings across the motor terminals

cant find any diagrams for a 4 terminal motor the only one i can find has 3

Dave

[paltibine]

Although the motor has 4 terminals, two of them are connected together so it’s effectively 3 terminal. There are only 3 wires to it.
With all the wires disconnected but still with the black box connected the only meaningful reading I got was about 2 ohms between terminals 1 & 4 which are next to each other on the right hand side. The black/grey wire we’ve been following is connected to terminal 1.

[electrofix]

the black box has that got any readings through it from the white wire ?

Dave

[electrofix]

the black box is the motor starting relay and they are still available

Dave

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