Replacing a Switchmaster 300 heating timer

Postby mdfenemer » Fri Jun 27, 2008 5:44 pm

Hi, My switchmaster 300 timer (the brown one with the dial on the left and rocker switch on the right) has stopped working. The timer face no longer turns. So I thought i would replace it, I went to B & Q and got a Sunvic 107XL.

I opened up the Switchmaster and saw that the baseplate,which was a lot bigger than the new one but had the same number of terminals labelled in the same way as the new sunvic ..N L 1 2 3 4.

I connected up the sunvic in the same way as the switchmaster was wired.. The timer unit came on but it did not fire up the boiler....

On closer inspection I noticed that the swichtmaster also has a link wires connected fom N to 2 and a wire from L to 4 and that there was no pin 3 on the back of the switchmaster.

I thought I would be clever and just take the wires off agian and wire them into the Sunvic 107xl in exactly the same order taking into account the missing pin3 and link wires . the Sunvic came on every time but when scrolling through the modes still the boiler did not fire.....So I have now taken back the sunvic back to b & Q to exchange it thinking that I had brought the wrong type...As I looked at the other makes on the shelf I realised that they are all the same....

Does anybody know how to wire these new type of timers to my aging Baxi WM30/3RS boiler which only has two wires from the switchmaster to the boiler itself and of course those link wires..... the power itself comes from a fused spur and of course will be connected to N and L. that bit I do understand.


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Simply Build It

Postby Paul4Lola » Mon May 26, 2014 6:48 pm

Hi, I have come across your question and wondered whether you ever received an answer. ?
I have a similar unit and my timer has stopped as well.
As yet I have not looked around but wondered if the replacement you found was any good ?
Please advise

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