I have a 240 wagon with a broken odometer, and a speedometer that will work under entirely random circumstances. The Speedometer, once working, will continue to work until the cars been shut off, the odometers never worked.

The odometer gears inside of the cluster looks fine, factory original stuff. I've had all contacts cleaned prior to re-assembly and a few bits in the teeth grooving cleaned up (the plastic circle the gear climbs around), fuses are in good shape too.

All other gauges and lights work fine so what could be causing this?

The trouble seems to be the speedometer not receiving power, or receiving inconsistent power despite all three wires going to it gripping their spots pretty good.

Somehow one of the speedometer pins wasnt making proper contact so O took care of that, it was one behind the face on the lower section.

If anyone has a fix or a known working speedometer they're willing to sell let me know.

 

I don't know specifically about your late 240 speedo, but on others, erratic problems are often due to old solder joints, and/or age-degraded capacitors.

 

I inspected the cluster again, the soldering points around the odometer motor look okay, capacitors arent in bad shape (but I honestly cant tell a good one from a cracked one).

The cables behind the speed sensor have a sag to them and a crack in the cover right behind the sensor. Previous owner did briefly fix the speedometer by tightening these up, I'm thinking thats where the issue is.

Hopefully I can run some tests this week using the cables by the spare wheel.

 

you can't see bad solder joints

a crack in the differential cover would let all the gear oil leak out.

 

I need to check the differential oil but from how the car feels it hasn't been leaking out, no unknown noises.

If the solderings old should I try re-soldering or just buy a known working speedometer?

 

I'm not sure you can just go out and buy a working speedo for a given version. My 92 740 has a flakey speedo, where the needle usually stops at 42mph and won't go any higher, I've recapped it already and that didn't help (several caps WERE swollen and crusty), so I probably need to pull it out again and resolder its whole board. the 91/92 740's have a unique speedo not interchangeable with later years and apparently they are notorious for doing this. but, 240's are different and I dunno what years are interchangeable
.

 

Hmm, when mine works it'd go up to wherever I was going, what are these "caps" that you speak of?

 

Check for bad wires coming from rear axle going into the car.

 

The two wires beside the spare tire are fine but I suspect they may not be making very good contact with the sensor.

If the wires are bad, what should I do to fix them?

 

They will look fine inside the car of course. Look FROM axle to car.

 

Chances are its the actual speedo. Swap for another one, but it has to be the right one. In your case ABS speedo so anything 1991?+ with ABS will work.

Again, get a multimeter, set it to ohms and learn how to trace a wire end to end. If you were motivated enough you can unplug wires at diff and check if anything comes out the other end where it plugs into the cluster! Get it?

 

Oui, my wording

I meant that the wires not making good contact are the ones to the rear axle , on the outside. No obvious frays but quite a sag to them.

I will plug my Mullimeter in when I find it in my mess of things.

 

one multimeter test would be to jack up one rear wheel with the other rear wheel carefully blocked, pull the speedo, and hook the multimeter up to the speedometer sender wires (the green-white and black wires at the 3-wire right angle connector, with it unplugged from the speedo), set the multimeter for AC Volts, and have someone spin that jacked up wheel (with the transmission in neutral), you should see maybe 1V AC pulsing as the wheel turns. if you see voltage pulses there, then the sender and wiring is fine, and your problem is definitely in the speedometer.

 

Oh and speedo model is printed on face. Varies by year and from wagon to sedan. Get it right!


Do not plug yellow wire for cluster to corner pin on cluster BTW! You get that wrong you can fry cluster.

 

ditto if the instrument panel doesn't have a tach, do NOT plug the red-white wire into anything, there's a place that LOOKS like it might go, but that also will fry stuff.

 

Right, this actually concerns me a bit though.

I'm not the first one to remove the cluster (as evidenced by a missing screw, small chip on the headlight panel, newer odometer gear, and missing metal bracket), someone else got there before me.

When I first removed the cluster I cant recall if the tach wire was plugged in, it shouldn't have been, this car never got a Tach until I installed one.

When I find my old Millimeter, or buy a new one, I will try to get some results in this week.

 

I saw your pics of dangling wires...

Scotch tape and label!

 

Yellow is speedo.

Yellow/red is shift indicator.

Red/ white is tach

I am 93.6% on those colors!

 

Augh, I should've brought some tape out, its all back together for now but when weather improves I'll get out there ASAP.

EDIT: My car will have an extra yellow cord for the cruise control, I'm certain that plugs into the bigger double spade, NOTHING touches the little one near the bottom beside the speedometer.

 

Yel goes to double spade. Speedo output.

Red/white goes to nothing unless you have tach.

Yel red goes to small spade on corner. Shift/overdrive indicator.