My grandson has a problem with the speedometer on his 1990 190E. Apparently one day last week while he was driving it at highway speed the needle began to wander up and down but mostly down until it went to 0. The car was still running along at the same 60km speed. I told him that my best guess would be the speedometer cable. The next day he texted me that the speedometer was working again but that afternoon it did the same as before and finally went to 0. He drives it to school everday and everyday the speedometer works for about 3 kilometers then wanders and quits.
Is this likely to be the cable or the speedometer itself?

 

So the speedometer works when transmission is cold it seems. I am not sure if the dial is powered or not. I assume not but have not seen a similar issue to base this on.
The mechanical part is hard to malfunction like this. It usually either works, works wobbly, or never works. Hard for it to cut out like your GS's car.

Just in case, you can jack up the car and check the securing nut at the transmission side but I doubt that is it.

May have to look at the wiring diagram at the cluster for this one. There may be a loose connection since you had to take it apart for the lighting fuse in the past couple years.

 

Dolucasi, I will have him come up for a visit now the snow is gone pretty much from the roads and he can jack it up in my garage. I find it odd that he says it comes and goes. If the cable was broken it seems to me it would just not work. Maybe with my woman's hands I didn't tighten the threaded nut down tight and it is loose allwoing the cable to slide back. But why only when it is cold does it work. I think the cluster might have to be pulled. He can learn to drive it on the tachometer like my husband did with his airplanes. LOL

 

Dolucasi, I will have him come up for a visit now the snow is gone pretty much from the roads and he can jack it up in my garage. I find it odd that he says it comes and goes. If the cable was broken it seems to me it would just not work. Maybe with my woman's hands I didn't tighten the threaded nut down tight and it is loose allwoing the cable to slide back. But why only when it is cold does it work. I think the cluster might have to be pulled. He can learn to drive it on the tachometer like my husband did with his airplanes. LOL

 

The only mechanical possibility I can think of on the transmission side is that the speedo cable is not fastened well enough and after a point is it is not spinning or rather it is slipping.
Only a very little likelihood for that, the way they are designed BTW.

On the cluster side, many would actually pay for your smaller hands to secure that speed nut. I'm sure you are OK there.
My simple Hanes electrical diagram does not show the speedometer as an electrical component that is powered up.
Which means it is just a magnetic coil gauge.

So if your transmission connection is not the culprit, I'm afraid you are in for a new speedometer or a repair of yours.

- Cheers!

 

Thank you. We will have a look and maybe replace the cable just to be sure. They are not that expensive.

 

Or, he can use his mobile phone's GPS, which often gives fairly accurate speed reading.

 

I feel compelled to warn you about the speedo cable replacement Laura. The aftermarket GEEMO (Sp?) ones are rather cheaply built. After my original started to be wobbly, I replaced my original with a Geemo one at around 180K miles.
Firstly, even though it was made specifically for a Manual transmission, compared to my original is was 5mm shorter. And the length needs to be very precise BTW. And after installation, the wobble was gone but it would make a winding noise behind the cluster. I think I either gave it away or chucked it. Also it did not have the padding the original had. Long story short the replacement from the dealer was about $140, twice the price of an aftermarket but it is a perfect fit and no more noises. It should outlast me and the car....

So my advice is to make sure and not damage the original during replacement and if you can get the Mercedes one where you are via mail, I would highly recommend it. This is all assuming dealership still has them. They may gone NLA. Perhaps the Classic center in SoCal can help you. They ship parts all over the world and do not mind doing so.

Happy Friday!

 

Thank you. I have a GPS he can use also. No cell service in my area. Too remote I guess and I use a land line.LOL

 

Thank you. I have been looking on the net and it seems the speedometer for the auto transmission ones are indeed NLA. I will check with the Classic Car Center and see what is available. It may not even be the cable son further investigation is necessary. I will get back when I have had a look with the GS. Thanks.
I just looked at the MB Classic site and can't find a aut trans cable. I see also that Bilstein/Febi makes one? It is less expensive than the Gemma one also? Maybe worth a try if one is needed at all.