Unusual combined light switch/dimmer

TerryBn · Sep 17, 2023

The house I've just moved into is fitted with the light switches shown in the pics. They are fitted to each bedroom and the landing. The landing light is also switched from a second standard switch on the landing as well as a standard switch in the hall. So essentially 3 way switching. I can't find any info on the internet and wondered if anyone has any knowledge of them. At least one of them flickers in certain positions and I'm probably going to replace with standard switches. Although difficult to see, the second picture says they are fused and the replacement fuse is listed as Crabtree list no 6925. So I wonder whether they are Crabtree switches. Anyway, I would be grateful for any information. Thanks, Terry

westward10 · Sep 17, 2023

I suspect it is Crabtree. Cant say I've ever seen one like that before but there has been a multitude of dimmer switch styles produced, no reason why it cannot be replaced with a standard switch. Note which terminals the wires go to before disconnecting and we are always happy to advise.
Can you see any other part numbers?

brianmoooore · Sep 17, 2023

Definitely a Crabtree 6925. I have one in my hand as I type.
It's one of the first 'quality' dimmer switches produced, dating back to the early '80s or late '70s.
They are only suitable for use with incandescent lamps, and are likely to cause flickering with any other type.
The fuse was only fitted to protect the electronics inside, which is much more susceptible to surges than modern components, and the whole thing can simply be replaced with a modern 2W switch. No fuse required.

brianmoooore · Sep 17, 2023

@westward10 It was in the same box of bits that I dug the similar looking MK dimmer switches out of for Lucien, last year.

TerryBn · Sep 17, 2023

westward10 said:
I suspect it is Crabtree. Cant say I've ever seen one like that before but there has been a multitude of dimmer switch styles produced, no reason why it cannot be replaced with a standard switch. Note which terminals the wires go to before disconnecting and we are always happy to advise.
Can you see any other part numbers?

brianmoooore said:
Definitely a Crabtree 6925. I have one in my hand as I type.
It's one of the first 'quality' dimmer switches produced, dating back to the early '80s or late '70s.
They are only suitable for use with incandescent lamps, and are likely to cause flickering with any other type.
The fuse was only fitted to protect the electronics inside, which is much more susceptible to surges than modern components, and the whole thing can simply be replaced with a modern 2W switch. No fuse required.

Thanks for the quick response Brian and Westward10. Led bulbs are fitted at the moment which explains the flickering I guess. To me its somewhat odd having dimmers to the overheads in the bedrooms and the landing light, so will change to standard switches. Given that the landing is switched from 3 positions. Is there anything I need to watch for?
Perhaps I'll see if there's a museum that wants the old ones.

westward10 · Sep 17, 2023

Before you disconnect anything take pics. Note what terminal each wire goes in, if there are wires of the same colour put marker pen dots on them to differentiate.

brianmoooore · Sep 17, 2023

Dimmer is marked com, L1 and L2. New switch may be the same, or marked L1, L2 and L3.
If this is the case, then Com = L1, L1 = L2, and L2 = L3.

TerryBn · Sep 17, 2023

westward10 said:
Before you disconnect anything take pics. Note what terminal each wire goes in, if there are wires of the same colour put marker pen dots on them to differentiate.

Will do and thanks again.

TerryBn · Sep 17, 2023

brianmoooore said:
Dimmer is marked com, L1 and L2. New switch may be the same, or marked L1, L2 and L3.
If this is the case, then Com = L1, L1 = L2, and L2 = L3.

Thanks Brian. Does that mean I need a one gang two way switch for the landing?
But will the bedrooms be ok with a standard one gang switch?

brianmoooore · Sep 17, 2023

Landing will need to be 2W and, if the switches by the doors in the bedrooms are the only switch, then they can be 1W, but a 2W switch can be used instead. Most 2W switches have a terminal marked "use for 1W" or something similar. You might be able to get a better price if you buy all identical switches.