Diode volt drop

[jimbo84]

The vax spotwash has packed up a couple of months out of warranty so pulled it apart. It’s failing to pump water.

Voltage to the water pump before the diode is 230v voltage after the diode is only 139v, way under.

The pump was quite hot. Tried it direct to a 230v supply, it sounds like it’s pumping but failing to move water.

Replacement pumps are available for a good price but don’t want to knacker the new one by sticking it on the end of a bad diode and it being under voltage.

Any ideas?

The pump


The diode, numbers read IN4007 MIC

 

[ajlelectronics]

Are you reading AC? A diode will half wave rectify it, leading to the result you see, as you are only now getting half of the waveform.

 

[jimbo84]

Are you reading AC? A diode will half wave rectify it, leading to the result you see, as you are only now getting half of the waveform.

Yeah AC. That confirms the reason then. I’ll get a new pump ordered. Thanks

 

[Robert Weaver]

Them pumps likely include a one way valve, so when the plunger oscillates back and forth under the half wave rectified voltage, it effectively pushes water in the direction the valve opens. Could be a broken valve.
I think I have a in4007 if you need voltage drop value, or a free diode.

 

[qwakers]

i had the same issue. the cheapest pump from ebay is better than the original and still working fine.

 

[carbon]

Remove the two screws on the one end of the pump and check the valves inside. Possibly one isn’t shutting correctly. Make a note of which way it goes back together.

 

[Turbo]

The pump will not work on direct ac power.
The diode is there to cut half the ac wave. That means the dc coil in the pump only gets power on half the wave, acting on the plunger inside to make it pump.
Those pumps usually have a mini circuit board with a few diodes on them, that looks very basic.

 

[jimbo84]

I’ve pulled apart the pump, there was a little valve stuck to the opening of the pipe so I’m hoping that was all it was. I’ll connect it back in later and see if it pumps water.

 

[jimbo84]

Rebuilt and working as it should.

Thanks to everyone who posted in the thread, I’ve learnt something and saved some money so happy days.