Odometer Rebuild Leads to MPG & OBC Problems?

[nitroracer]

I removed the instrument cluster from my 87' IS last week to rebuild the odometer with some new gears from garagistic. While the gears were easy to swap out, I managed to take one step forward and two steps back. When I re-installed the cluster in the car the odometer still did not work, and I lost my previously functioning MPG gauge and OBC functions related to mpg and fuel.

For the odometer, I was able to move the gears by hand and spin the numbers up. Leading me to believe the problem could be with the odometer drive motor itself. Any other ideas here? The speedometer itself works fine, just no recording of the mileage.

The MPG gauge was working before I pulled the cluster and now it swings between 0-Max MPG. No throttle but moving is infinite mpg, but any throttle and the gauge plummets to zero. So I still have some sort of signal or connection, but I don't know what to check here.

The OBC functions were working before I removed the cluster as well, MPG, Range, etc. Now those are not changing or not reading anything at all. I was thinking this maybe related to the single wire plug that goes into the back of the cluster in the green connector? I moved it to a different location but didn't have anything change in the way it operates.

Any help would be appreciated. I pulled the cluster back out and broke out the multimeter to start fishing around.

[jlevie]

If the SI board batteries are old, pulling the cluster for any length of time can push them over the edge and affect the MPG gauge, temperature gauge, tachometer, or OBC. Or any combination of those.

[Poorboyz]

Contact Gregs///M on here. He rebuilds these cluster. I just had my rebuilt by him and he does top notch work.

GL

[nitroracer]

Taking a closer look at the SI board, I think mine may have been replaced or rebuilt at some point in its life. There is a translucent red coating over most of it, and the batteries are newer lithium cells each reading 3.03-3.04 volts. I don't see any obvious blown or burnt out components.

[Tom.]

tighten the ground nut on the back of the cluster, and also loosen the screws on the plastic cover that covers the gears. also try backing the tiny little o-ring that holds the gears on the shaft off a little bit.

[nitroracer]

I fixed the problems with the OBC and MPG gauge, the green connector that plugs into the back of the cluster wasn't seated properly and had missed the pin it should have been plugged into. Reset that and the functions returned.



Still no working odometer yet. I did notice that I need to bring the two pins holding the gear stacks closer together in order to install the plastic cover. Is that typical? I can still turn the gears by hand, but the motor does not appear to do so. Maybe I can test the motor with a pair of test leads and a 12v source.

[Gregs///M]

I can tell you that your SI board is dead or near death. The red coating was applied during production of the SI board in the 1980's. Battery voltage of around 3.00 volts indicates a dead battery. New batteries have voltage around 3.25V.

Also, there is a plastic cover with two screws that protect your odometer gears. If you over tighten those screws, the odometer will not work. Back those screws out and barely tighten them, that usually works.

The green connector is simply speed signal OUT to the cruise control. It should not have anything to do with the OBC or MPG gauge. Those are both powered and controlled by the SI board so I suspect you will see failure again soon unless you replace SI batteries.

[nitroracer]

Thanks for your input Greg. I'll get a new pair of batteries before these ones completely fail on me.