The car is a 1993 400E. Originally the odometer stopped working so I took the cluster out for repair by a specialist. He fixed an issue on one of the circuit boards and replaced a few gears. After installing it in the car and taking a few trips I noticed it would only work intermittently but would usually be dead. For example, it wouldn't work at all for a whole drive but would work perfectly the next drive, and so on. So I took the cluster back to the specialist where he tested it right in front of me. It worked perfectly and counted miles continuously when connected to his tester. The strange part is that the speedometer has always worked flawlessly/accurately, meaning its not likely to be the speed sensor. I'm almost certain the biodegradable wiring harness was replaced a few years ago because it seems to be in excellent condition.. so it can't be that. I tried researching info about the actual sensor sender on the transmission housing but I can't find any information about it. Its very confusing because the cluster is obviously receiving the speed signal because of the working speedometer. From what I've been told, that one signal supposedly drives the speedometer, which the odometer runs off of. I'm really not sure what to do next, as I know this issue is usually solved after replacing the broken gears.
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400E Very Strange Odometer Problem
- Thread starter Joncf
- Start date
Any chance you could temporarily swap in a spare/used instrument cluster from a different 400E/E420?
The biodegradable wiring harnesses are on the engine - there are two of them, one up top for the injectors/etc, and a lower one to the starter/alternator/etc. The harness which goes to the transmission (including the speed sensor) is totally separate, but I've not heard of anyone reporting failures of this harness - which is good, because it's been NLA for years.
The biodegradable wiring harnesses are on the engine - there are two of them, one up top for the injectors/etc, and a lower one to the starter/alternator/etc. The harness which goes to the transmission (including the speed sensor) is totally separate, but I've not heard of anyone reporting failures of this harness - which is good, because it's been NLA for years.
Unfortunately I don’t have an extra cluster to swap in. It doesn’t seem likely to be a harness/wiring issue. Wouldn’t the speedo be affected the same way if it was? Is the vehicle speed sensor on the transmission a replaceable part? I can’t seem to find anything on it.Any chance you could temporarily swap in a spare/used instrument cluster from a different 400E/E420?
The biodegradable wiring harnesses are on the engine - there are two of them, one up top for the injectors/etc, and a lower one to the starter/alternator/etc. The harness which goes to the transmission (including the speed sensor) is totally separate, but I've not heard of anyone reporting failures of this harness - which is good, because it's been NLA for years.
The speed sensor on the transmission is not available separately, it's an integrated part of the transmission wiring harness. You are correct, there is a single speed signal from the transmission to the cluster. The same signal drives both the odometer and speedometer. If the speedo always works, it's not the sensor.
Sounds to me like either one of the odometer gears is bad (maybe he didn't replace all of them), OR the electronics are faulty. You can buy a used cluster/speedo and then manually adjust the mileage to match your car - or, have a VDO shop adjust the miles.
Sounds to me like either one of the odometer gears is bad (maybe he didn't replace all of them), OR the electronics are faulty. You can buy a used cluster/speedo and then manually adjust the mileage to match your car - or, have a VDO shop adjust the miles.
Occasionally on my first drive on colder mornings my (electronic) speedo needle does not move at all while the odometer works normally.
Driving for 2-10 minutes and the needle always has started registering on its own and working normally thereafter.
Or a light tap to the left side of the dashboard above the speedo always gets it working normally as well.
Gotta’ be a mildly oxidized or slightly loose contact back there...
Driving for 2-10 minutes and the needle always has started registering on its own and working normally thereafter.
Or a light tap to the left side of the dashboard above the speedo always gets it working normally as well.
Gotta’ be a mildly oxidized or slightly loose contact back there...
