bosch rd 532 combi

[Hobo128]

Got call to boiler, no hot water or heating. got voltage into Boiler, got 240v from pcb to pump and about 200 ohms at pump. Fan works, gas valve works, ignition works as manage to get it fired up by chance, but then I shut it's self down. Pump didn't seem to be spinning though so I'm looking at that. Just a bit confused as has voltage from pcb to pump and resistance was okay.

Any ideas

 

[stevetheplumber]

If you have voltage and the pump isnt spinning theres a clue there

 

[kris]

Can u spin the pump shaft freely when powers off or is it stiff ,

 

[stani]

Just been to a 37CDi today, pump was free as a bird, but boiler would go to U6 and then shut down, voltage to pump, but didn't work, 15 mile trip for new pump and everything back to normal,
But, I always thought sequence required flow from pump before fan would run and boiler would fire, this didn't?

 

[Hobo128]

Can u spin the pump shaft freely when powers off or is it stiff ,

Yes, I can spin the pump, it's not stif

 

[Hobo128]

If you have voltage and the pump isnt spinning theres a clue there

Thought so, just though the resistance would be out though

 

[Hobo128]

Just been to a 37CDi today, pump was free as a bird, but boiler would go to U6 and then shut down, voltage to pump, but didn't work, 15 mile trip for new pump and everything back to normal,
But, I always thought sequence required flow from pump before fan would run and boiler would fire, this didn't?

It actually says in the manual that the pump is the first in sequence, this is what's confused me as the boiler did fire at one point.

 

[stani]

It does throw you a bit, but this would fire and then immediately overheat, no movement of water, had screwdriver on pump trying to listen for movement but nothing.

 

[Kevin D]

No flow or pressure sensor in that boiler, what's going to check the pump? The line in the manual is probably a cut and paste from something thirty years old. If the flow NTC senses any change in temp it will fire.

 

[Hobo128]

Okay to wrap up this post I ordered a new pump and changed it. Boiler fired up fine. In actual fact I only changed the head.
something to point out though, when I removed the old pump it wasn't seized up and it was getting voltage, I checked the resistance of it which was about 150 ohms (new pump was 180 ohms) so I think resistance was okay. The only thing was that the old pump smelt burnt,shouldn't the resistance of the old pump have been way out. Just not sure what was actually the problem with it