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

[seeker]

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.

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]

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

 

[Cid]

Looks like an intermediate switch.

 

[chris gray]

are you swapping for a plastic switch?

 

[westward10]

Looks like an intermediate switch.

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

 

[seeker]

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]

are you swapping for a plastic switch?

Hi Chris yes MK Y1843

 

[seeker]

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]

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]

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]

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]

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]

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

 

[Lucien Nunes]

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]

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.

 

[westward10]

As you say he has viewed the switch upside down.

 

[Lucien Nunes]

Yes, I expect the common terminal is strapped to the adjacent blind one internally, and that each feeds separate moving contacts for L1 & L2. Then, to make an intermediate, the blind terminal is replaced by a normal one without the link, and both moving contacts have both a NO and an NC fixed contact, crossing over between L1 and L2. Some speculation here, as I don't think I've ever taken one of these apart. I might not even have seen one in the flesh.

 

[seeker]

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

There were wires in the untapped terminals. As I reported the old switch works. The old switch can take 7/8 inch depth of cable. Modern switches can hardly accommodate multi-wire cores as they are two small in both depth and width to hold the cores tightly. I have had to use connecter strip and reduce the old multi-wire cores to solid core. In the loft there are four or more junction boxes that are involved in the wiring. As the old switch worked fine, as far as I know I am not keen to interfere with the wiring. The house wiring is ok but owing to the use of wooden back boxes it is tricky to access them. The switchplate screws are of the wooden screw variety. On some backboxes I have had to plug the rear of the box as the sides of the wooden box have become too weak to take screws.

 

[seeker]

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

There were wires in the untapped terminals. As I reported the old switch works. The old switch can take 7/8 inch depth of cable. Modern switches can hardly accommodate multi-wire cores as they are two small in both depth and width to hold the cores tightly. I have had to use connecter strip and reduce the old multi-wire cores to solid core. In the loft there are four or more junction boxes that are involved in the wiring. As the old switch worked fine, as far as I know I am not keen to interfere with the wiring. The house wiring is ok but owing to the use of wooden back boxes it is tricky to access them. The switchplate screws are of the wooden screw variety. On some backboxes I have had to plug the rear of the box.

As you say he has viewed the switch upside down.

Yes, when a lightswitch is unscrewed to inspect its connection it is convenient to record the wiring as it is visible.

 

[Lucien Nunes]

So far, it seems that although it was working, you have a non-standard complement of cables, incorrectly connected to the original switch. You want advice how to correctly connect them to the new switch, without tracing anything. I don't think this is going to fly.

If the cable configuration was one of the popular recognisable ones, and/or correctly connected to the old switch, we'd be able to help but I think you would have been able to do the job anyway. It's not, so we can't assume anything, i.e. it's time to trace.

One last-ditch attempt - are you equipped with an ohmmeter or continuity tester to discover how the old switch functions? We could check the contact configuration relative to the blind terminal and deduce the functions of the cables. I know other posters are going to say get a spark in, and I'm inclined to agree, but it's not rocket-science!