19 replies to this topic

[mike.]

The MOT has ran out on my mini and its got a couple of minor issues that'll stop it from passing, but i'm at a loss of where to start fixing them. 

 

The speedo - Has a new cable fitted, its not broken and is well oiled/greased. The problem is the speedo doesn't work the majority of the time. Sometimes it'll work for 2 mins, then just drop off and not work again for a month. I've taken the speedo end off and been for a drive, the cable spun for a while and then stopped and I couldn't get it working again. What could the problem be here? The cable is engaged because you can't spin it by hand so what can make it work intermittently? Could the gearbox drive end be faulty?

 

The horn - Used to work fine, worked for the MOT last year, but recently I realised it wasn't working. I've tested the earth on it and thats fine, I tested the voltage and it's only getting 0.2v from the horn wire. So unless there is some huge resistance somewhere, the wire itself can't be broken if some voltage is getting to it. 

 

Where could the problem lie? My main beam flash (pulling stalk towards me) also doesn't work, despite the little tabs in the stalk making a good connection - could this be related? 

 

I took the cowling off and couldn't see anything blatantly loose or not connected, it all seems nice and clean in there. Am I right in thinking the horn is the black/purple wire? 

 

 

 

If there isn't an easy fix i'll just wire the horn through a push switch to get it through the MOT, but ofcourse i'd rather get it working properly off the stalk. 

 

Thanks!

[M J W J]

Check your fuses for the horn. I think you may find that your hazard lights don't work if the fuse to the horn has gone. 0.2v is what a lot of multimeters will just fluctuate by. If you are only getting that down it I would suspect that you have bad continuity down that wire.

 

As for the speedo not working it sounds like the drive gear is missing a few teeth. Either that or have you made sure that the cable is securely fixed to the gearbox and hasn't come loose there. If it lifts up it can disengage from the gearbox.

[lewBlew]

Pretty sure speedos aren't part of the MOT for a car. Obviously you want it fixed (and it's illegal to drive a car without one) but just so you know, it's not tested in the MOT.

[mike.]

Checked the fuses and they are ok, and hazard lights are working fine.  

 

The speedo - I think i've read speedos have been added to the MOT this year. I think I may be able to get away with it as the garage I take it to will drive it at most 10 metres in and out of their booth so may not realise its broke. Unless they'll check it on the brake roller I don't know. 

 

Can the speedo drive be changed easily? I see on minispares I don't think new ones are available, only second hand for £22! and they're out of stock...

 

I don't get why it works sometimes and not others. If it had teeth missing wouldn't the needle just jump around at least rather than just sit there doing nothing?

[KernowCooper]

If the cable is tight and correctly located its got to be in the speedo drive gears so undo the retaining bolt on the assembly and lift it out and check the nylon drive gear, and yes class 4 cars the speedo function is now a requirement but its only a test to see it working.

[mike.]

Ok well speedo drive is the main suspect then - Not looking forward to that giving how hard the cable itself is to get at!

 

Any other ideas on the horn? I'm at a loss with that.

[Dan]

  The horn and flasher are on the same fuse (the flasher is not on the same circuit as the rest of the lights) so if both have failed the problem is probably somewhere around the fuse holder.

[mattbeddow]

Surely if its illegal to drive a car without a working speedo, it would be an mot failure f they spotted it, regardless of wether it was in the test or not

[mike.]

No, theres a difference between whats legal and whats safe enough for an MOT. Legal stuff is enforced by police. 

 

I've been using a speedo app on my phone for a speedo which is about 5mph more accurate that my speedo anyway. 

 

I'll check out the fuses today - Wouldn't be the first time i've had a problem with a dodgy fuse box connection!

Edited by mike., 12 June 2013 - 08:17 PM.

[mattbeddow]

But surely if its not legal then its also not sefe enough for an MOT...

[Dan]

  No, the MOT doesn't claim to cover every part of the Construction and Use or Road Vehicles Lighting Regs.  It checks your car is safe, not legal.  It's the driver's responsibility to keep the car legal, the MOT makes sure it's safe enough to be around other people.  The speedo is now covered though, but has only been so for about the last 2 months.  It just has to work the accuracy isn't tested.

 

  It always amuses me that people just assume when their GPS or GPRS speedo shows a figure which is different from the mechanical one, the digital thing will automatically be the more accurate.

[mike.]

It always amuses me that people just assume when their GPS or GPRS speedo shows a figure which is different from the mechanical one, the digital thing will automatically be the more accurate.

 

Well that is an interesting thought... 

 

I'm basing it on the fact that my cars got a metro engine fitted and different size wheel/tyres than standard so assume the mechanical gauge is a bit off. 

[Dan]

  No you are probably quite right, don't get me wrong.  It's just funny that people, and I do it myself, are more comfortable believing something that relies on satellites and an unbelievable amount of maths than a simple device that essentially just counts how many times the wheels turn.  I've posted before about the way I think the accuracy of both machines behaves, I just find it odd.

[1984mini25]

Ok well speedo drive is the main suspect then - Not looking forward to that giving how hard the cable itself is to get at!

 

Any other ideas on the horn? I'm at a loss with that.

unscrew the cable for the gearbox end and give the cable and were it screws onto the gearbox a good clean, as if you have a bit of dirt/grit in the threads it will still screw on and feel like its on properly even though it isn't.

[mattbeddow]

Seeing as how the police use GPS to check your speed when they follow you, i think its safe to assume the gps is more accurate.

you have to remember that speedos deliberately over read so they air on the side of caution.
Could you imagine the fallout if it was discovered that everyone in a certain car were getting tickets at 30 when their speedos were reading 30 but the car was actually doing 35?