Speedo Jumps

[tom_kauf]

Hi everyone,
I'd like an opinion on a problem I have with my (85 190E) Speedo.
It works fine above 40kmh and seems accurate, but below 40kmh it jumps up and down. For example when braking at traffic lights, the needle will jump up and down between the 0kmh stop and the actual speed.

I checked the Haynes service manual, and I think it might be friction problem with the Speedo cable. Do you think that could be it?
I want to take apart the dash anyway.
Does the speedo cable actually go up to the speedo, or is it electric at that end?

Thanks for your help, :thumbsup:
Tom

 

[carabind]

I don't know if you have an electric or cable speedo- others far more knowledgable will know and be along soon. But if it is cable - I have suffered similar in the past. The inner cable does "dry out" with age and mileage, then tend to "flick" around within the outer cable rather than turn smoothly. The best way around this is to replace the cable.

Or, take the old cable out completely, pull the inner out and lubricate with some WD40 or similar. Look for any kinks or sharp bends in the outer cable - if severe, you'll need a new one, Be very careful to clean off any surplus lubricant at the speedo end - if too much gets in you'll ruin the speedo head. You can do a bit of diagnosis also, by connecting up the cable end to say an electic screwdiver and seeing how smoothly it turns before and after the lube.

 

[tom_kauf]

I don't know if you have an electric or cable speedo- others far more knowledgable will know and be along soon. But if it is cable - I have suffered similar in the past. The inner cable does "dry out" with age and mileage, then tend to "flick" around within the outer cable rather than turn smoothly. The best way around this is to replace the cable.

Or, take the old cable out completely, pull the inner out and lubricate with some WD40 or similar. Look for any kinks or sharp bends in the outer cable - if severe, you'll need a new one, Be very careful to clean off any surplus lubricant at the speedo end - if too much gets in you'll ruin the speedo head. You can do a bit of diagnosis also, by connecting up the cable end to say an electic screwdiver and seeing how smoothly it turns before and after the lube.

Some excellent ideas carabind,
I'll try the screwdriver trick, because I couldn't get the steering wheel off, to get to the Instrument Panel (I even broke a socket, that's how tight it was). That way I can start at the other end of the cable. It won't fully solve the problem until I get the whole cable out to lubricate it, but it's a diagnosis start.
I'm glad that lubricating it might solve the poblem, rather than having to get a new speedo.....we'll see how it goes.

Thanks,
Tom

 

[C220GJS]

You have a cable driven speedo on your car, and the symptoms you describe point to a dry cable.Buy or borrow a good quality socket for removing the steering wheel bolt and give it another try as you will not be able to lubricate the cable properly unless you can withdraw the inner cable.
Use something like silicone grease for lubrication,but do not use WD40 as it is not intended as a lubricant and dries out in a short time (it works ok as a penetrating oil for loosening parts and as a water dispersant for damp electrics;hence the name WD40).
Geo.

 

[tom_kauf]

You have a cable driven speedo on your car, and the symptoms you describe point to a dry cable.Buy or borrow a good quality socket for removing the steering wheel bolt and give it another try as you will not be able to lubricate the cable properly unless you can withdraw the inner cable.
Use something like silicone grease for lubrication,but do not use WD40 as it is not intended as a lubricant and dries out in a short time (it works ok as a penetrating oil for loosening parts and as a water dispersant for damp electrics;hence the name WD40).
Geo.

Oh, ok. I'll get some Silicon grease. The bolt for the steering wheel is an 10mm internal Hex head (in other words an Allen Key type). I couldn't get enough leverage with the short allen key, so I used a 10mm socket with a long extension. But I guess the socket wasn't made for those sorts of sideward forces.
Thanks C220GJS

 

[C220GJS]

Getting that bolt off is a two man job ,get someone to hold the steering wheel steady ,don't rely on the steering lock or you will damage it. You will need an allen head socket,a short extension and a breaker bar, it is very tight as you have found,when replacing the wheel the bolt should be torqued to 59lbft or 80Nm.
Geo.

 

[television]

These days its better to use Teflon,PTFE and silicon oils, very low friction and they do not go hard or dry out. Available from Cain saw people and Screw fix.

malcolm

 

[tom_kauf]

Hi malcolm & geo,
Oh, ok thanks. I'll look into the other types of oils.

Yeah, the Haynes service manual said to put the key in the ignition to avaoid the steering lock engaging. I think I will get an allen key Head for my ratchet, and it's good to know what to tourqe it to (i've got a tourqe wrench).

 

[tom_kauf]

EXCELLENT! I got the speedo out without removing the wheel.
The electric screwdriver trick showed me that the speedo gauge itself isn't jumping.
Now I just have to grease the cable and try it out.

(ignore the numbers, that's for the post where my 'EXH Temp' light isn't illuminating)

But I have one question. I have 3 Wires with a single pin, which went into position A and B, but the 3rd one was not connected.
Where could it go?

Every gauge was working, but it may have come off when i was removing the Speedo cable.

 

[tom_kauf]

Done

Hi everyone,
I've finished greasing the Speedo Cable and re-installing the Speedo cluster. I won't know if it worked until I drive it, which is another couple of weeks away because it still isn't registered yet.

Thanks for all your help ,
Tom