wiring new lightswitch to replace old MK 4526 2 way 2 gang

seeker · Dec 22, 2018

Hi I am replacing all the lightswitches in a C1950 bungalow. The photo below is of a 2 way 2 gang MK 4526. It has a row of terminals at the top labelled: Common, 2,Common,2. The bottom row is unlabelled. I need to know how to connect a new MK lightswitch.

[ElectriciansForums.net] wiring new lightswitch to replace old MK 4526 2 way 2 gang

A drawing of the existing wiring is below. Please note that switch terminals 1 and 3 are untapped hence no screws.

Also note that the three cord (no earth cable ) has red ,white, and blue cores.

westward10 · Dec 22, 2018

If terminals 1 and 3 are untapped how have you got wires in them?

Cid · Dec 22, 2018

Looks like an intermediate switch.

chris gray · Dec 22, 2018

are you swapping for a plastic switch?

westward10 · Dec 22, 2018

Cid said:
Looks like an intermediate switch.

Can't be if two of the terminals don't serve a purpose.

seeker · Dec 22, 2018

westward10 said:
If terminals 1 and 3 are untapped how have you got wires in them?

Hi Westwood10. Puzzling but, but my drawing is an accurate reproduction of the way the switch was wired. The terminal holes are 7/8 inch deep. The wires are flex so could be just a "push fit". Anyway that is the way the lightswitch was wired.

seeker · Dec 22, 2018

chris gray said:
are you swapping for a plastic switch?

Hi Chris yes MK Y1843

seeker · Dec 22, 2018

westward10 said:
Can't be if two of the terminals don't serve a purpose.

The location is two way not intermediate, but as I reported the untapped holes wer being used. It would be nice to get information from MK.

telectrix · Dec 22, 2018

don't think you'll get anywhere without a spark visit to test/trace the cables, see what they do, then wire new switch as needed.

seeker · Dec 22, 2018

telectrix said:
don't think you'll get anywhere without a spark visit to test/trace the cables, see what they do, then wire new switch as needed.

I have already, replaced the three core cable with new three core and earth as the blue core (and only the blue core) in the original installation had crumbled to nothing if touched. I took the uptmost care to make sure that the wiring in the loft was connected in the same way as before. What I am requesting is information about how the old switchplate can be wired to a new switchplate (as the old switchplate worked OK). I have established connection to the 2nd switch that is to a garage external light (2 way) So the other switch should work as there are only two terminals (unmarked) to connect to below the top row.

westward10 · Dec 22, 2018

The untapped holes cannot have been in use and I could certainly give a good prediction of where the conductors should go but as Tel says in #9 only someone on site can guarantee correct connections. Cables with red, white and blue cores are probably long past their reasonable service life and you are indicating crumbling insulation which suggests the installation needs urgent attention for continued safe use.

Lucien Nunes · Dec 22, 2018

Noting that the OP has already replaced the red/white/blue triple, that colour combination was used with plastic insulation briefly in the 60's, and all examples of that cable I have seen have been in good condition.

This is one of the first versions of the familiar MK 2G switch, from before the triangular layout. AFAIK where it says 'Common 2 way' that all refers to the terminal with the screw. Simply ignore the presence of the untapped brass bush. Then, L1 and L2 are the terminals at the bottom of each gang. In that case although Seeker seems to have taken care to note what was where, I also suspect an error in that the switch was probably upside down. Agree that on-site testing is required to verify, as there are too many question-marks. If wires were indeed poked into the untapped holes, whoever fitted it didn't do it right even though it worked.

I don't think we have one of these in the museum. Perhaps I could persuade Seeker to post it over once the mystery is solved (all costs reimbursed of course).

westward10 · Dec 22, 2018

Red, white and blue was also used in rubber cables which probably explains the deterioration.

Lucien Nunes · Dec 22, 2018

Indeed - it was the standard colour code for triple TRS and very smart it looks at the terminations. I have been searching for a decent length in good nick and found some nicely protected within 3/4 slip conduit serving a remote pushbutton station for a starter. Haven't pulled it out yet.

westward10 · Dec 22, 2018

Lucien Nunes said:
Noting that the OP has already replaced the red/white/blue triple, that colour combination was used with plastic insulation briefly in the 60's, and all examples of that cable I have seen have been in good condition.

This is one of the first versions of the familiar MK 2G switch, from before the triangular layout. AFAIK where it says 'Common 2 way' that all refers to the terminal with the screw. Simply ignore the presence of the untapped brass bush. Then, L1 and L2 are the terminals at the bottom of each gang. In that case although Seeker seems to have taken care to note what was where, I also suspect an error in that the switch was probably upside down. Agree that on-site testing is required to verify, as there are too many question-marks. If wires were indeed poked into the untapped holes, whoever fitted it didn't do it right even though it worked.

I don't think we have one of these in the museum. Perhaps I could persuade Seeker to post it over once the mystery is solved (all costs reimbursed of course).

So you are saying common two way is no more than the common terminal with the opposing two your commonly known L1 and L2.