As I mentioned in the last post, the speedo has jammed with the needle stuck on 60 kph. It reads over 60 just fine but when the vehicle speed drops below this point, the needle obstinately stays in the middle of the dial.
The most likely cause is that the fly spring on the back of the needle has failed. There are some folks out there repairing period auto speedos so I figured if I can get the fly spring out I can order a replacement of the same rating from the UK… well that was the plan.
I found a very interesting article online by Anthony Rhodes on how to strip and rebuild a Jaeger speedometer. So after some bedtime reading, I was ready to go. This is perhaps the only repair on a Land Rover not requiring the use of a hammer!
Mechanical description from Mr Rhodes…
The speedometer (speed indicator, not odometer) functions in just the same way as a tachometer. The cable spins a thin bar magnet. Just in front of the bar magnet is a disk mounted on a spindle. Also attached to this, on the same spindle, is the pointer that is visible over the dial face. When the bar magnet spins, it causes the disk (drag cup) just in front of it to try to spin as well. The amount of twisting force (torque) imparted by the magnet to the disk is proportional to the rotational speed of the magnet. If the magnet spins twice as fast, the torque is approximately twice as great. The spindle is attached to a flat coiled return spring to resist rotation. The amount the spring winds is proportional to the torque. In this manner, the pointer moves progressively farther as the magnet spins faster. “
Speedo and manual
Remove the trip meter reset knurled screw
Remove the glass and bezel and… err, staple?
Mechanism removed from the case by way of extracting the 2 screws on the rear. With a bit of fiddling the trip reset shaft came out easily enough. The trip (top) and odometer (bottom) wheels can be seen behind the face.
To remove the face, the needle needs to be extracted. This is simply a press fit. With the needle pointing to 0kph I made a small scratch on the drag cup local to a landmark on the frame of the speedo. This will allow the needle to be refitted in the correct location.
With the needle removed (it simply pulls off) the two tiny screws holding the face on can be extracted…
… leaving just the mechanism. Now the fun begins.
Using the vice from the pillar drill to hold the mechanism, the trip reset shaft can be removed.
It’s important to take lots of reference photographs. The tiny split pin needs to be removed to free up the gear on the shaft.
Once the sprung steel pin (top middle) is removed from the nylon sleeve (top right), the whole shaft is withdrawn from the top of the mechanism.
Next to come off is the trip meter wheel assembly. A very, very, very, small spring needs to be removed first. This spring holds the brass pinion against the gear. It can just be seen to the left of the number 7 digit… and if it ends up on the floor… it’s lost forever.
Then the odometer wheels come off the base plate. Another tiny spring to be extracted.
This is where the magic happens… Drag cup and what’s left of the fly spring…
The drag cup lifts out and the rotating bar magnet is revealed.
An element of cleaning to the frame is required
The bar magnet lifts out and the frame is almost naked.
I could have gone further with the stripping down of things. The frame still has the 2 tufnol gears and pinions could be removed. The trip and odometer wheel sets cold also be rendered down to component parts. The purpose of the exercise; to access the fly spring has been achieved.
Upon assessment of the condition of the fly spring and a bit pf further reading, I don’t possess the mechanical means to establish which weight of fly spring to replace it with. It’s important the spring is of the correct rating otherwise the needle wont read correctly.
I have ordered a new old stock Land Rover speedometer from PA Blanchards.
The original unit will be sent for a full restoration by http://www.magnetic-speedometer-repair.com in the UK. He has the correct machinery to get calibration spot on where as I don’t.
Although I cant fix it myself, I really enjoyed the mechanical simplicity of the magnetic speedometer. It’s not all that hard to take apart, the only “special” tools required were a optometrists screw driver and a thin bradawl. I tried to avoid magnetised tools too. The face of the speedometer is pressed aluminium and very fragile so this needs some careful handling… as I learnt to my cost.
Time to put things back together.
With the frame cleaned up a little bit the bar magnetic is dropped back into position
There is really no chance of salvaging the spring. It seems to be pressed into the brass ring on the drag cup… best leave it where it is for the time being
Drag cup sits neatly above the bar magnet. The bearing for the drag cup is a jewel in the centre hole of the bar magnet assembly.
I’ve learnt recently, the tiny springs are easy to remove than to refit. Both go back on without too much fuss.
Frame with full compliment of parts. It’s possible that the black numbers of the right of the frame (203 15) relate to the spring rating, or is it the 85 on the drag cup… answers on a post card please…
Trip reset shaft back in position. It got straightened before being refitted.
Now for the tiny split pin (at the end of the pointer)
Somehow I managed to change to the odometer to read 202 km… should be 20,202km. Not that it matters a great deal, it’s been round the clock twice !
The face is refitted. Another number… 46… could this be a spring rating?
Mechanism and bowl
Speedo frame, seal, glass and bezel.
The tangs on the back of the bezel are peened down with a parallel punch to keep it secure.
Back together and ready for shipping to the UK… and it’s the first and last time it will ready 120 kph! Hopefully 🙂
Hi l have just found the article on the jaeger speedo strip,
one thing l found on my speedo was the friction disc was rubbing in the magnet, l tried adjusting the setting where the needle spindle protrudes but it didn’t make any difference, on
close inspection l found the remains of the minute end of the spindle which had broken off allowing the friction disc to sit too low in the inner bearing surface and rub on the magnet, so l will now have to try and get the speedo repaired by a professional company, l found the photos and description brilliant, well done. I hope my comments help people my problem was easily missed being such a small part, also l need a new regulation spring, l was using the speedo for my classic motorcycle as it looked like the Smiths speedo.
Thanks again Dave Cox
Hi Dave, Thanks for leaving a message and the kind words, sorry it’s take as long as it has to respond. I was amazed the speedo is as serviceable as it is… but I never managed to get it to work accurately. I had a hard tailed BSA A10 long ago and that had a Jaeger speedo… off something. I sold it to a local collector when i left the UK and he was going to restore it back to original condition. It had a lovely engine, restored by SRM. All the best. Andy.
Les, really liked your tutorial. I have a Smiths speedo in my MGA, installed a new cable , now the speedo doesn’t register when driving, disconnected the cable while driving, it’s turning. Removed the speedo and hooked it up to a drill, it works, next thing I’m going to try is disconnect the cable from the trany and drive it with a drill. Do you have any thoughts on what is causing this , I’m out of ideas. Thanks in advance , Bill
Hi Bill, Sorry for the delay.
The first thing that springs to mind is; are you 100% sure the cable is engaging with the speedo head correctly? Does the odometer still work? It’s not unheard of for aftermarket speedo cables to be too short at one end or the other. If you’re sure the cable is engaged correctly then you’ve have done the obvious tests and diagnosed the speedo head is at fault. Without opening the thing up, its hard to pinpoint the issue though. The likeliest cause is that the fly spring on the back of the needle has failed and is jamming the needle on zero. Changing the spring isn’t all that complicated but you need a special machine to calibrate the drag cup so the speedo reads correctly. There’s a few good folks restoring Smiths and Jaegers in the UK.
Hope this helps and apologies again for the delay in responding.
Regards
Andy
Hello Little Green Landy
here is a German owner of a little green Frogeye Sprite who needs some help.
I read the tutorial from Mr. Rhodes and I read yours and looked at all the pictures. (Fine work!)
Many years ago my Speedo doesn’t work propery. No real speedo to read. The tripmaster was working pretty well. Becaus of that I handed it to VDO in Witer and got it back. It was working properly for a few weeks. Than the same stuff. Back to VDO: “You cable is to long and pushes the bearing out.”
I shortened the cable and nothing changed. So I didn’t make any further attempt to repair it. The tripmeter worked and that’s what I needed. As the tripmeter stopped working now I had to do something.
So I opened my speedo and the first fault I saw was the missing screw that “fixes” the needle. The brass one on your first picture. As I understood I need it for adjusting the axial play of the needle. But what would be the right measure? Do you have any idea?
I minimized the play against “0” and took it back to the car. Tripmaster okay, speedo
goes over 160, High Beam and smashed to the post from the wrong side.
No, it’s not the spring I dismantled it a second time. I think it must be the axial play.
Thanks again for you very good report and pictures.
Regards
Ragnar
Little Green Landy 
It will need setting to Zero.
Do you know if there is a Transfer for the face?
For the gauges as well?
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Hi l have just found the article on the jaeger speedo strip,
one thing l found on my speedo was the friction disc was rubbing in the magnet, l tried adjusting the setting where the needle spindle protrudes but it didn’t make any difference, on
close inspection l found the remains of the minute end of the spindle which had broken off allowing the friction disc to sit too low in the inner bearing surface and rub on the magnet, so l will now have to try and get the speedo repaired by a professional company, l found the photos and description brilliant, well done. I hope my comments help people my problem was easily missed being such a small part, also l need a new regulation spring, l was using the speedo for my classic motorcycle as it looked like the Smiths speedo.
Thanks again Dave Cox
LikeLike
Hi Dave, Thanks for leaving a message and the kind words, sorry it’s take as long as it has to respond. I was amazed the speedo is as serviceable as it is… but I never managed to get it to work accurately. I had a hard tailed BSA A10 long ago and that had a Jaeger speedo… off something. I sold it to a local collector when i left the UK and he was going to restore it back to original condition. It had a lovely engine, restored by SRM. All the best. Andy.
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Les, really liked your tutorial. I have a Smiths speedo in my MGA, installed a new cable , now the speedo doesn’t register when driving, disconnected the cable while driving, it’s turning. Removed the speedo and hooked it up to a drill, it works, next thing I’m going to try is disconnect the cable from the trany and drive it with a drill. Do you have any thoughts on what is causing this , I’m out of ideas. Thanks in advance , Bill
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Hi Bill, Sorry for the delay.
The first thing that springs to mind is; are you 100% sure the cable is engaging with the speedo head correctly? Does the odometer still work? It’s not unheard of for aftermarket speedo cables to be too short at one end or the other. If you’re sure the cable is engaged correctly then you’ve have done the obvious tests and diagnosed the speedo head is at fault. Without opening the thing up, its hard to pinpoint the issue though. The likeliest cause is that the fly spring on the back of the needle has failed and is jamming the needle on zero. Changing the spring isn’t all that complicated but you need a special machine to calibrate the drag cup so the speedo reads correctly. There’s a few good folks restoring Smiths and Jaegers in the UK.
Hope this helps and apologies again for the delay in responding.
Regards
Andy
LikeLike
Hello Little Green Landy
here is a German owner of a little green Frogeye Sprite who needs some help.
I read the tutorial from Mr. Rhodes and I read yours and looked at all the pictures. (Fine work!)
Many years ago my Speedo doesn’t work propery. No real speedo to read. The tripmaster was working pretty well. Becaus of that I handed it to VDO in Witer and got it back. It was working properly for a few weeks. Than the same stuff. Back to VDO: “You cable is to long and pushes the bearing out.”
I shortened the cable and nothing changed. So I didn’t make any further attempt to repair it. The tripmeter worked and that’s what I needed. As the tripmeter stopped working now I had to do something.
So I opened my speedo and the first fault I saw was the missing screw that “fixes” the needle. The brass one on your first picture. As I understood I need it for adjusting the axial play of the needle. But what would be the right measure? Do you have any idea?
I minimized the play against “0” and took it back to the car. Tripmaster okay, speedo
goes over 160, High Beam and smashed to the post from the wrong side.
No, it’s not the spring I dismantled it a second time. I think it must be the axial play.
Thanks again for you very good report and pictures.
Regards
Ragnar
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