Reusing ends to make up speedometer cable
 

Seems nobody has W124 cables in stock except a couple questionable Ebay listings. Mine was sheared right in the middle, but I pulled the ends and both look clean and intact. I've been driving with a GPS unit but that doesn't get the cruise control working!



Since it appears the inner square cable just plugs into the fittings on both ends as usual, is there any reason I can't carefully remove them, get a standard Dorman cut to length cable, and fabricate some sleeves to crimp/epoxy/otherwise attach the Mercedes ends?


Is the square cable maybe metric sized or something tricky like that?

Consider finding an inner cable from any other Benz of sufficient length and putting your ends on it. You may even be able to reuse one of its existing ends. I'm thinking that the Benz cable would be of better quality and the correct size for the casing. Worth looking into if a BMW cable would fit. Is there a manufacturer name on the casing?

I have a new cable pm me

This should be the correct transmission end.

Thanks for the pic, I'll jack up the car today and pull mine out to check, as I reinstalled it to keep crud out of the housing.

Ok, here are the ends of mine.

Transmission end OD is slightly under 16mm (probably 16mm bore in trans)
Inserted length including rubber 19mm, measured from corrosion line.
With rubber removed, overall length not including barb is 18mm.
Square cable is .100" across the flats.

This is Mercedes part #124 540 13 68 marked only with this number and the star.

Let me know if I captured it all or if you'd like more.

Thanks, your cable looks like it would work, but the nose is clearly different without the groove for the rubber part to snap into. That's not a big deal as it looks like an O-ring could be installed on the post, is that how it's intended to seal?

I'm not certain but I do see what you are talking about. An o ring is on the speedo end which looks like it serves no purpose?

I think that on my transmission that rubber end is what seals dirt from getting into the speedo gear, I think that probably putting a regular O-ring on the end of yours would probably do the same job. Otherwise they look pretty equivalent, I'm not sure why both exist and are different.

Success! Thanks Dieselbenz for sending the cable. I just popped the rubber end off the transmission end of my cable and installed it on the new one. There is no groove, but it doesn't need one to retain it as it's inside the bore.

There are several different bushings on the cable for the different route that it would take, but I just sliced them off. Speedo is working fine, though the needle was a bit slow to respond at first probably from years of being stationary.

Cruise control also works but was surging unless climbing a hill. However it also hasn't worked in years, and my testing was minimal. I'm making a trip to the city tomorrow where I can give it some exercise on the highway and see if it straightens out.

Hey hey great make certain the motor driving the cruse control is less than 1 amp or it will take out the power transistor. Those motors come appart easy enough and new Silicon lube should bring it back to under .1 amp draw.

Thanks for the tip, I will pop it apart and clean it up, also it looks like the common advice is to reflow the amplifier PCB and check for bad caps.

Looks like it's a simple DC motor on pins 4 - 5 of the actuator connector, I assume 12V and reversed with an H bridge, so just test it with plain 12VDC for current draw? No need to energize a clutch or anything?

I'll probably check that quick in the morning before I head off to the city tomorrow, so I know if I can try it out on the road or not.

Yes 12 vdc on 4 and 5 with you meter in series.

Only 150mA and seems to work well, tested the clutch as well.

The issue is likely that the needle is bouncing a little, I suspect the cable was a bit longer and I may have bent it a little tight while trying to find a route that protects it from road gravel. I thought I swept it in pretty gently but when I get home I'll jack it up and try to make an even gentler curve.

I noticed a new behaviour today, which was after coasting down to make a turn off the highway it seems to be downshifting to 1st gear and revving up a lot more when I accelerate. Before it would just lug up to speed in second unless I asked for more power, which I preferred on our icy roads.

Coincidence or is the speed sensor used in transmission control?

That’s cool you got this fixed. The needle bounce is likely some kind of binding in the sleeve as you suspect.

I am a little late to this thread. For future reference you can build up these cables by brazing them with a propane torch and brass wire. Get the tips clean and flux them up with borax laundry booster.

My dad helped me fix my Volvo speedo when I was 16 this way. RIP dad. The tip had broken off and he made a new one by silver soldering a square steel shaft to the end of the cable. The speedo worked again but it bounced. I never figured out why (I was just a kid and just kept driving the car). Reading your thread it occurred to me the cable was too long. Dad must have rebuilt it a tad too long and it was binding in the sleeve. That thing is like a big spring so it slingshots as it binds and makes the needle oscillate.

Bouncy needles can also be remedied with greasing the entire length of the cable. But I bet you’ve done that already. Likely it needs to have it is either too long or too short by a tiny amount. You can test the theory by loosening the yoke a bit and backing it out while driving it.

Did some troubleshooting on the bouncy needle today, yes it seems like the inner cable is a tiny bit too long. Loosening the nut and pulling the dash cluster out makes the needle run smooth and the cruise work perfectly.

I added some o-rings around the post to stand it off a bit, only works if the cluster is pulled out. Ground a very small amount off the end of the cable and now it works great with the cluster out and is marginal when pushed in. It worked then bounced again, then I tugged back on the outer cable a bit and it ran smooth.

Going to trim the inner cable a tiny bit more tomorrow and hopefully that will do it.

I decided something was up so rather than trim it further I grabbed my remaining half a cable and decided to attach it to the cluster, spin it with a drill, and move the cable in and out. Turns out that it ran the smoothest when it was under a little pressure, so something was up if the replacement was happier loose.

Pulled the inner cable and it turns out mine doesn't have this ferrule thing and it must have been rubbing against something when the cable nut was tightened.

Sliced it off so only the regular square end was present and now it runs super smooth :thumbup1:

Thanks for sharing! Glad you nailed it.