Fluctuating speedo (1972 swb series 3)

My speedo intermittently fluctuates anything from a 5 mile to a 20 mile wobble. It all started to happen when I had the garage add in a cigarette lighter (which could be coincidental). They have suggested to buy a new speedo head.

I have two issues:

1. Which is the right speedo head for my landy?
(current speedo does not have a trip meter and is in mph)
2. Do I really need a new speedo head?

If anyone could help me I would be very appreciative, as i do not want to throw money at the landy when it might not need it.
I put enough in it for petrol

had they taken instrument panel out as if they did probably disturbed speedo cable. possibly head but new with trip about £120 but try cable first

I trapped the cable when I was messing around with the dash, bounced around all over the place. Free'd it off so it wasn't trapped and had no twists or kinks and it was fine.

Spyderman said:

I trapped the cable when I was messing around with the dash, bounced around all over the place. Free'd it off so it wasn't trapped and had no twists or kinks and it was fine.

Click to expand...

As above, mine was fine till about 40mph, when it said you were doing between 30 and 50!
The above was the prob.

Be glad that yours shows a speed....

Mine has read 0 for the past few months....

I would say its almost certainly the cable that's at fault, if it's been disturbed go over it again and make sure its correctly routed with no twists or kinks before you spend any money.

If the cable was removed it's easy to not quite put it back properly. Pull the cable off the head and reseat, making sure the plastic bit clicks in properly. I ended up lifting a rear wheel and getting my son to spin it to rotate the cable inner while fitting to the head to make sure the squared off bit engaged properly. If it doesn't work try a new cable before replacing the head.

Thanks everyone, I will have a look at the cable over the weekend. It will be my first go at doing anything myself (apart from moving a door handle from one door to the other) so lets hope it all goes well.

mine was not working at all, was fluctuating as you described, I bought a new cable and it made no difference

I dismantled the head and found that the little steel dish which is attached to the needle was rubbing. hard to describe but because it rubbed it would stop moving, then jump as it freed up

I think the speedo works via two magnetic heads which spin next to the dish (magnetic bits are attached to the cable) and drag on it

its a fiddly job, but not actually that hard and my speedo is fine now

45mins work roughly


*edit to say that the cable did actually have an issue, but someone pushed too hard on the back of the speedo head