MK Grid Fuse Modules - any tips

[JohnW2]

Hi folks,

Any tips? MK Grid (modern) fuse modules. I know that it is often a pain to get the fuse out, but I've just encountered one which has, so far, beaten me. It's the 'ususal' (at least, for me) problem - undoing the screw brings the fuse carrier out about 3-4mm, but the screw then 'disengages' and just 'spins' and the fuse carrier won't come out. It screws back in fine (pulling the fusecarrier back in), and I've been through the 'screw in, screw out' cycle umpteen times - but the fuse holder won't come out, despite the maximum amount of 'brute force' which I dare (or, have so far dared!) to apply. Short of just increasing the amount of brute force until I probably break the thing, does anyone have any other tips or ideas?

Kind Regards, John

 

[securespark]

Have you tried unscrewing it and pulling it at the same time?

 

[JohnW2]

Have you tried unscrewing it and pulling it at the same time?

Yep, unfortunately, many times - that seemed like the most obvious thing to try. Maybe I just have to keep trying!

The saving grace is that the urgency has gone out of the situation (although I obviously need to resolve the issue). The fuse hadn't blown at all - I have subsequently discovered that the circuit wasn't working because some kindly soul has switched off an isolator

Kind Regards, John

 

[EFLImpudence]

I cannot help. Some just seem to be like that.

Presumably not made very well.

 

[JohnW2]

I cannot help. Some just seem to be like that. Presumably not made very well.

Thanks. That's what I feared. I guess I'll just have to increase the level of brute force until either it comes out or breaks - I'll report back It's hard to imagine what it's 'catching' on; the screw is certainly 'disengaging' from whatever it screws into.

Kind Regards, John

 

[333rocky333]

Put a screwdriver behind the carrier side and lever out as you turn the screw.
To be honest usually after that there knackered, when you break one open you will see why, there are two small exposed live pins and im sure they weld on to the fuse after use
I have encountered the same about twenty times now, however i have one sheered from new on the van just through trying to fit a lower rated fuse

 

[JohnW2]

Put a screwdriver behind the carrier side and lever out as you turn the screw.

I tried that, but was frightened to lever any more violently, because I felt (I now think correctly) that I would break off the 'lip'. However, as below, I now realise that trying to pull/lever before the screw is fully undone is probably futile, and probably could only damage the carrier - one needs to fully undo the screw before applying any violence!

To be honest usually after that there knackered, when you break one open you will see why, there are two small exposed live pins and im sure they weld on to the fuse after use. I have encountered the same about twenty times now, however i have one sheered from new on the van just through trying to fit a lower rated fuse

I have actually now triumphed, with brute force (pliers tugging on carrier, after fully undoing screw), without doing any obvious damage. Asabove, if what I'm seeing is typical, I don't think that pulling/levering whilst undoing the screw is appropriate, since one is then merely trying to break the carrier from the screw. Once the screw is fully undone (and 'disengaged') it seems that what's holding the carrier in is whatever plug/socket arrangement it has at the back (I presume the 'pins' you mention), which is incredibly tight. Even having got this one apart (and 'in and out' a few times), it's still very tight, so I'll probably replace it (if I can find one that isn't so tight!

Kind Regards, John

 

[333rocky333]

I now realise that trying to pull/lever before the screw is fully undone is probably futile,

The thing works like a worm drive surely you would have to lever while you turn otherwise you damage the thread housing and the screw breaks out.

The screw shouldnt come right out but when it unexpectedly does which ive only encounterd once , you can eventually take the carrier right out and just slide it in and out, refitting the screw may secure it, but personally i to would maybe replace it, i also found sometimes there was no output anyway once the problem occured

 

[JohnW2]

I now realise that trying to pull/lever before the screw is fully undone is probably futile,

The thing works like a worm drive surely you would have to lever while you turn otherwise you damage the thread housing and the screw breaks out.

It acts as a worm drive for that first 3-4mm of fuse carrier movement, and that part of the exercise always seems to work fine (at least, for me) - but, as I said, after that, the screw clearly disengages from whatever it was 'worming' and becomes totally loose (i.e. 'just turns and turns' without doing anything, but remains 'captive'). It's then that one discovers that the carrier is 'stuck' in by it's pins/socket or whatever - from which sufficient force will free it. However, at least whilst the screw remains captive, the carrier does not come completely out.

Kind Regards, John

 

[333rocky333]

Oh I get you now, i cant say ive noticed the screw turn and turn i thought it just stopped, but i get what you mean, that normally after a point it releases and the draw slides in and out.
I take it your draws still captive then, so you cant see the innards, I will take a pic of the "pins" when i have time for you to diagnose the problem
I take it youve tried it without a fuse incase the fuse is slightly longer than normal

 

[333rocky333]

Oh I get you now, i cant say ive noticed the screw turn and turn i thought it just stopped, but i get what you mean, that normally after a point it releases and the draw slides in and out.
I take it your draws still captive then, so you cant see the innards, I will take a pic of the "pins" when i have time for you to diagnose the problem
I take it youve tried it without a fuse incase the fuse is slightly longer than normal

Edit
I was in buckinghamshire last week, thought of you

 

[JohnW2]

Oh I get you now, i cant say ive noticed the screw turn and turn i thought it just stopped, but i get what you mean, that normally after a point it releases and the draw slides in and out.

Yep, that's exactly what I meant. The screw 'wormed out' the carrier by 3-4mm and then 'released' it, and then (in my case) just 'turned and turned'. However, although 'released' from that mechanism, that carrier/drawer was 'well stuck', I presume by those pins at the back.

I take it your draws still captive then, so you cant see the innards, I will take a pic of the "pins" when i have time for you to diagnose the problem

Yep, the drawer is still captive, so it would be interesting to see a piccie sometime. Mind you, I'm probably going to replace this one, anyway, so will be able to do some destructive examination of it

I take it youve tried it without a fuse incase the fuse is slightly longer than normal

Yep, it's exactly the same with no fuse - it just seems that the pins are an extremely tight fit in whatever 'sockets' they go into at the back.

Kind Regards, John

 

[JohnW2]

I was in buckinghamshire last week, thought of you

Probably not my bit of Bucks, though - I'm in the 'top-left-hand corner', yards from Oxfordshire and (if the wind is blowing in the right direction!) within earshot of the cars at Silverstone, in Northants! I can't say I get to Essex all that often, but FWIW I was born in East Anglia, albeit Norfolk!

Cheers, John

 

[333rocky333]

- it just seems that the pins are an extremely tight fit in whatever 'sockets' they go into at the back.

Kind Regards, John

Its not what youd expect, compared with previous models, theres no socket and pins, as such, i know the grid ones 90 degree out, but on the spur theres just two sort of pointed metal pins one left and one right, that just seem to jab into the fuse end, i think putting them in under load could easily arc and weld them, not suggesting thats been done in your case

 

[JohnW2]

Its not what youd expect, compared with previous models, theres no socket and pins, as such, i know the grid ones 90 degree out, but on the spur theres just two sort of pointed metal pins one left and one right, that just seem to jab into the fuse end, i think putting them in under load could easily arc and weld them, not suggesting thats been done in your case

Oh, I see. No, that's not what I was expecting. I was thinking that there was probably either some pin/socket arrangement, or else the fuse got pushed back into some sort of 'fuse holder clips/prongs' (as seen in plugs). If it's just pins 'jabbing into the fuse end', that makes it less clear what can be hanging onto my fuse carrier so tightly! As you say, mine clearly aren't welded, because I can put the fuse in and out, and it's still very tight.

Kind Regards, John