TOP TIP - Y Plan motorised valve actuator

[malc_p]

Just fixed my mother-in-law's central heating!
She had exactly the same prob I had 4 years back - heat not getting to the radiators although boiler, pump, stats etc working fine and no airlocks.
Checking the pipes into and out of the three-way valve, it's HOT from the pump, HOT to the Hot Water cylinder and COOL to the radiators. The actuator was not moving under any conditions although all the electrical signals to it were correct. The normal advice would be to replace the actuator - at 75quid plus VAT.
Now, I'm not a plumber but have been an electrical engineer in the past so thought "let's have a shufty". Long story short, one of the microswitches was not operating correctly. Unsolder it and replace it with a 50p job from Radiospares, BINGO!
Exact same as the problem with my system, so it looks like a common fault.
SO - if you have a multimeter and a soldering iron, ***isolate the electric supply to the system*** and check that the microswitches operate when you click them, save yourself some money.

 

[seco services]

don't make any sense at all.
if the heating pipe wasn't getting hot then as you say the motor wasn't working.
so what has the micro switch got to do with the motor not moving across as the microswitchs aren't activated till the motor has moved the valve across.

 

[MANDATE]

I think it does make sense! Power to drive the motor goes through the first microswitch, so if this is faulty on the related contacts the motor won't move. (2 sets of contacts) Likewise if the other set of contacts in the same microswitch is faulty, it could explain why some valves won't go further than mid point.
Although the microswitch is triggered at mid point (switched from 'white wire to 'grey' it is active from the start.
I've only had a problem with second microswitch, which when triggered did not allow power out of the 'orange wire'.
This second microswitch, although triggered just after mid point is active from the start. It provides the power to the PCB for the modified voltage, which of course is no longer required, once the 'grey' has taken over from the 'white'

 

[seco services]

yes agree the way you have written it makes sense i couldn't get my head round how the op had put it.

 

[superdupergasman]

This tip works for s plan systems too...

I have never gotten just a new switch tho, just butchered a new valve and use inline connectors, then kept the motor for another repair.

 

[malc_p]

As Mandate said, the motor gets its power through the first microswitch's "Normally Closed" contacts from the CH wire (white in my case). So when CH was activated, the motor got no power so didn't move to the A/B position.
Took the switch to pieces, problem was burnt-out contacts, same as you get on ignition points on a car because of arcing.

 

[MANDATE]

The only down side to your tip is knowing which microswitchs to order and how long it takes to get them.
You would need to dismantle and accurately indentify type size etc, then wait how long?
Out of interest what MV have you got and which of radiospares 1000 microswitches did you use.