Help please with econometer problem

[Sleepless]

Hello guys!
I own a BMW E30 318i (M40), late 1988 with only 62K kilometers.
The only thing which is not functioning properly is the econometer, which moves on the other side when I turn on the car but stays there regardless of the speed. The Si board batteries (NiCD) have been replaced and I also to replaced the tachometer/econometer combo instrument - nothing, the problem persists.
Any ideas?

Thanks in advance for your replies,

George

[paultv]

From the Wiki:

Econometer
The econometer is dependent on the tachometer and the speedometer; therefore, anything that stops these two will also affect the econometer.

However, if these two are working normally but your econometer is not (especially if it reads Minimum or Maximum, but nothing in between) then the fault usually lies in the interior circuitry; the econometer is not receiving a speed signal from the speedometer. This is most likely caused by failing/ burnt out circuitry, or leaking SI batteries, and the only practical solution is to replace the dash cluster.

Paul

[Sleepless]

Thanks Paul, I've already read the article. My Si board looks like new (no spilled battery fluids) and the batteries are also changed.

I don't know if the capacity of the batteries is correct because the were installed from the previous owner. The original Varta were 500mah NiCD, these are not NiCD for sure (NiMH) and probably have a higher capacity. Could this be the issue?

[paultv]

The battery capacity won't affect anything. If all else is functioning correctly, then the finger points to an onboard component failure.

You also may have a simple dry joint on the board - re flowing all the connections might fix it - bit of a long shot!

Brian may well pop up here with alternative advice.

Paul

[Brianmoooore]

NiMH batteries in place of NiCd and their capacity is irrelevant.
There is no electronic circuitry on the econo/tacho instrument itself. It is simply two independent analogue meters built into the same case.
The econometer does not use any signal from the tacho. circuity. It uses the fuel rate signal which comes from the engine ECU on a white/black wire that changes to yellow/white at the cluster, and a road speed signal that comes from the electronics on the speedo circuit board.
The one case I have had of a non functioning econometer on an otherwise fully working car was found to have an obviously damaged (burnt) component on the speedo board and another damaged component on the SI board. I didn't know which board had caused the damage to the other, so I took the easy route and changed the whole cluster.
Check that the throttle position switch for the throttle closed is working properly.

[Sleepless]

NiMH batteries in place of NiCd and their capacity is irrelevant.
There is no electronic circuitry on the econo/tacho instrument itself. It is simply two independent analogue meters built into the same case.
The econometer does not use any signal from the tacho. circuity. It uses the fuel rate signal which comes from the engine ECU on a white/black wire that changes to yellow/white at the cluster, and a road speed signal that comes from the electronics on the speedo circuit board.
The one case I have had of a non functioning econometer on an otherwise fully working car was found to have an obviously damaged (burnt) component on the speedo board and another damaged component on the SI board. I didn't know which board had caused the damage to the other, so I took the easy route and changed the whole cluster.
Check that the throttle position switch for the throttle closed is working properly.

Thanks a lot Brian, I was afraid that this would be the answer. I guess I'll have to live with it, because clusters in good condition are very rare to find (and very expensive too).

Cheers

[Sleepless]

Just a quick update on the issue

Finally, I managed to find a Motometer Si Board in good condition. I changed the batteries, swapped it with the old one (VDO) and voila: my econometer came back to life