(Be sure to visit the links given at the end of this post for more info.)
Saturday I finally made time to work on the odometer. There are two prevailing repairs talked about on the internet if you Google for “924 odometer repair.” Each fixes a different gear that goes bad. One is on a shaft connected to the top odometer numbers and the other is on a shaft driven directly by the worm gear connected to the speedo cable.
My repair wasn’t really about either of those, but about the small red worm gear at the end of the shaft driven by the worm gear. Confused? Good.
The little red worm gear had moved down the shaft and was not fully engaging its companion gear. Further the shaft it is on had quite a bit of side-to-side play (not up and down), so the white mesh gear that is driven by the speedo cable worm gear was loose and not making consistent contact. This caused a sad clicking noise whenever you drove the car.
Below is a picture of the disassembled speedometer.
(Note that the speedo is upside down on the table.)
By pushing the red worm gear back onto the shaft, and also moving the white gear on the shaft up in its place, this seemed to (1) stop the clicking noise and (2) made the red gear have constant contact with its mate.
I turned the assembly with a battery-operated drill at low speeds using a torx bit. I did this literally for an hour before beginning work to try and fully understand how the unit operated. Turns out the clicking noise was being caused by the red gear slipping out of its groove with its mate. Believe it or not, but none of the gears showed any signs of wear or cracking.
After experimenting with the position of the two gears on that shaft and being satisfied they were working I put a drop of epoxy onto the end of the red gear to keep it from slipping.
One other area that my repair differs from others is that I could not get the trip odometer numbers to work. Inside the white plastic housing with the two sets of numbers I could clearly see the gear between them moving, but the trip numbers just wouldn’t move. I stopped short of disassembling the remainder of the speedometer for fear of breaking it and losing calibration on the speedometer itself, which was previously working.
Since the trip numbers weren’t working I had no real way of seeing if the main odometer was working, since I didn’t want to hold a drill on it for 10 minutes for fear of stripping out the area where the speedo cable bit fits into.
So I decided to re-insert the speedo back in the cluster, button it up and try it out. Got it all back together and tried it out, and the main odometer numbers do in fact work now. It would be great to have the trip odometer, but someday I will have to buy a rebuilt unit or have this one refurbished to make that happen.
One other thing I did while the instrument cluster was out was to fix the temperature gauge. It had some sort of tab blocking the gauge, which probably means its readings were inaccurate. The following picture shows what it looked like.
Turns out it was a label that had come unglued over 23 years. When turned over it said “12V”. To get it out I had to do the same procedure as with the odometer, by patiently prying off the metal bezel surrounding it with a small flat-blade screwdriver, then pulling off the plastic cover, then turning over the gauge to let the label fall out.
Getting the instrument cluster out
Here is some background on getting to the speedometer. On my 1987 924S it was simply not possible for me to reach my hand under the dash and push out the tachometer, so as to gain access to the speedometer cable to remove it. Some other accounts I have read said this was no problem, so I’m assuming it was on earlier model 924’s. I even tried getting on my back in the floorboard to reach around the other direction, from the temp. gauge side. That was tight but not as bad.
But the speedo cable was on tight enough that with the tiny amount of space and leverage I had, I could not get it loose. Also there was not very much slack in the cable at all, so I couldn’t really just push it out and get to it that way. (Yes, I opened the hood and pushed through as much cable slack as there was, which was very little.)
So the only option left was to remove the steering wheel, signal/wiper controls and trim pieces and pull the instrument cluster out as a whole. Removing the steering wheel was very easy as is described elsewhere; you just remove the horn pad and take off the single 24mm nut holding the wheel on. (Make sure your front wheels are straight and mark the position of the wheel on the shaft with fingernail polish.) Then pull the wheel off.
Gently pry loose the 3 electrical connectors attached to the column’s turn signal and wiper switches with a small flat blade screwdriver. Then remove the two screws holding the top and bottom plastic trim pieces on. Be careful as there are tiny tabs that will break off. The bottom piece comes off relatively easily with some wiggling but the top piece is more fussy. Just be patient and don’t break anything. God only knows if you can even find these parts any more.
Remove the three screws holding on the column assembly and pull it out.
Next there are two screws in the top of the instrument cluster holding it in. Unless your car is like mine and they were missing. My car seems to have lots of missing screws and bolts. Remove those two screws and gently start working the cluster out. If your car is like mine and has a “dash cap” then you will have to work it past those pieces also.
If you’re right handed like me, twist the cluster clockwise so the tachometer is closer and gently reach your hand behind the speedometer and work that cable off by unscrewing the metal cap. I needed a small set of pliers to get mine free, so be careful of all those delicate wires back there.
Once the cable is free you can pull the cluster out a few more inches and disconnect all the electrical connections.
You would think that now it would be easy to get the gauge out, right? Yeah. The literal sticking point is that each gauge has a rubber strip around it helping to hold it into the cluster. So be careful working it out as the cluster housing is flimsy plastic.
Once your speedo is free you need a small flat blade screwdriver, such as a jeweler’s or eyeglasses size, to gently pry up the metal bezel a little bit at a time to be able to pull it off the front. Again this will take time and patience, but don’t worry about all the little marks and bends you are putting into the metal as they will not show when everything is put back together.
Take off the plastic cover and the inside trim ring. Then remove the two main screws in the back. On mine there was also a tiny circuit board held in place with two screws that I removed. The gauge will then slide out of its metal housing, ready to be poked and prodded.
I think I failed to mention that not only did my odometer not work, but at low speeds like under 25 mph, my speedometer needle would bounce. Try explaining that one to a cop. The only way to try and cure this, short of replacing the cable, is to try and lubricate it. So when reassembling everything, I followed the advice of others and put a few drops of automatic transmission fluid into the speedometer cable housing. The clearances were so tight inside the dash that I am unsure how much good that really did, but it is a good preventative step. And my needle no longer bounces, although that was possibly tied to the “clicking” I was getting where the odometer gear was slipping.
Oh, and one more thing. I have read that a common cause of odometer failure is resetting your trip ‘meter while the car is moving, causing one or more of the gears to strip. After seeing how many delicate plastic gears there are in that thing I can believe it. So I took the spring that causes tension on the reset shaft (sticks out of the front of the odometer) and moved it to hook behind it onto a piece of plastic so that there was no tension on the trip numbers and no way to push the button. Since my trip meter was not working anyway, why not?
Following are some other pictures of the process. I got so wrapped up doing the job I forgot to take a picture of the dash with the instrument cluster removed.
Horn pad off, about to remove 24mm nut holding the wheel on.
Wheel off, next are the trim pieces and column switch assembly. This was all pretty easy to do.
Woohoo, now the real fun can begin. Note the dash cap. Mine is in pretty good shape but on top of the dash there is a piece missing, so I will have to replace it at some point.
Links
Here are some links to other articles and pages I have found on this subject.
Speedometer Service/Odo Repair (this page has lots of great pictures – click on one to zoom)
Fixing a Broken Odometer (the text that goes with the above link’s pictures)
Clark’s Garage Message Board – Odometer not working
924Board.org – Odometer Repair
