mystery si board

[mike65italy]

Ok here is my problem. I have just replaced the dash on my car, marked all the connections with tape labeling them where they went for the installation, and I figured i would change out the si batteries since I had the cluster out. Took apart the cluster to find out that there where no batteries on the si board, and everything was working fine. I had tach signal, economy gauge was working, fuel and temp working just fine. All this with no batteries in the si board. But there is the space and connectors for the batteries, just no batteries. Since I had the batteries, I installed them. Put everything back together, and now my tach and econometer do not work anymore. I checked to make sure I reconnected the c101 or whatever it is on the passenger side that feeds the signal to the tach and econometer, and it is connected. Checked the fuses, and they are fine. I double checked the connection on the back of the cluster, wiggled it around a bit, and everything is connected. Im at a loss here, it was working fine before with no batteries, now I installed batteries and it doesnt work.

I know power is going to the tach, becuase when i shut off the vehicle it jumps a little before settling resting. I had disconnected the battery during the dash install to keep anything from shorting. Can that send a signal to the ecm for some reason, and should I try disconnecting and reconnecting the battery?

Im just really confused.

Thanks.

[mike65italy]

Any of the veteran e30 drivers know anything that could have done this???

[Gregs///M]

Make sure you plugged your coding plug back in.

[reelizmpro]

First you have to ask yourself how is it working fine without the batteries? It probably has an aftermarket battery less SI board from Programa. A picture would have helped here. Not sure why you would try to install batteries when it was working perfectly fine but live and learn.

[mike65italy]

coding plug is installed correctly.

And if it was a battery less si board, wouldnt it have resistors then? I looked up the Programa si board and they still look like they have batteries. And I installed batteries because the dipsh*t PO had done the external battery mod, but had taken the external battery box. And I hadnt realized this till I began to research E30's more. And before I installed ther batteries the temp and fuel gauge were all over the place. So that may be why I installed batteries into the SI board. But thanks for the input.

[reelizmpro]

Beyond the correct polarity, did you verify that the Li Ion batteries were charged?
You probably have separate issues with the speedo and/or cluster traces. Time to troubleshoot.