odometer is working intermittently

Post by **januwan** » 17 Jul 2021, 12:28

A few days ago I zeroed my odometer (the car was stopped) and my odometer stopped working. I thought the gear was broken but the next day, after driving to my office and leaving the car in the parking lot (exposed to the sun) it started to work again. The same happened already three times. In the morning it does not work but when I drive home it does.
I was told it could be an ABS module. I upgraded mine a few years back.
Any help greatly appreciated.

Post by **misha** » 17 Jul 2021, 13:36

Odometer on 850 have nothing to do with abs...as long as speedometer works.

If speedo is working intermittently along with odometer...that would be the sign of bad abs module or abs sensors.

Do you have abs/tracs light ON when engine is running?

Post by **januwan** » 17 Jul 2021, 14:12

No, I don't have any warning light ON and the speedometer is working fine.

Post by **misha** » 17 Jul 2021, 14:40

Then ...it's gears in odometer...which will fail completely...pretty soon.

Post by **januwan** » 17 Jul 2021, 15:16

Why would it work when the car is hot? Those plastic gears do not expand to engage at the higher temperature and contract at lower one. It looks more like an electrical connection.
I agree that it would indicate gears failure especially when I noticed it after zeroing the trip counter

Post by **misha** » 18 Jul 2021, 03:14

Don't know why but mine did that too...and pretty soon they failed completely at 181k km.

Post by **RickHaleParker** » 18 Jul 2021, 04:12

januwan wrote: 17 Jul 2021, 15:16 Those plastic gears do not expand to engage at the higher temperature and contract at lower one.

A plastics without a coefficient of thermal expansion ... wow! You got a name for that wonder plastic?

Post by **abscate** » 18 Jul 2021, 05:26

RickHaleParker wrote: 18 Jul 2021, 04:12
januwan wrote: 17 Jul 2021, 15:16 Those plastic gears do not expand to engage at the higher temperature and contract at lower one.
A plastics without a coefficient of thermal expansion ... wow! You got a name for that wonder plastic?

ShrinkRap....a new genre of Psychologist Musicians

Post by **januwan** » 18 Jul 2021, 10:27

The gears are made out of ABS (most likely) which will expand 10 µm per 1 °C. This would result in 200-300µm expansion which cannot be the reason my odometer does not work properly. That is what I was trying to say. Of course, plastics expand but in this case, it is negligible.
It is better to say nothing if you don't have anything constructive to add.

Post by **RickHaleParker** » 18 Jul 2021, 17:22

januwan wrote: 18 Jul 2021, 10:27 but in this case, it is negligible.

If it is in good condition. Right on the edge is another matter. Clearly, it is not in good condition.

What drives the odometer? Pictures are worth a 1000 words.