ok heres the deal, i replaced the batteries on the board for the instrument cluster reinstalled it and now nothing works from the gas/temp to the speedo/tach, i did some research and on bigcoupe group they say batteries usually dont fix the tach/speedo , because its the leaked batterie acid causing the problem , so my car is going back on the road in a month and i need to have my speedo working i called BMW and the cost of a new board is 700.00 cnd my pinion thats a rip off , another route would be programa or bav auto witch are still in the 300.00 us range and not as bad but , there is a guy on ebay selling refirbushed ones for my 03/86 build date for 70.00 us, weird thing is my board looks diff then most i see,if in my situation what would you do,personally BMW is out of the picture to much $$$ , should i try the ebay special or should i just spend the $$ at bavauto or programa, i dont wanna spend the money and have something that dosent work!
anyone out there that went thru this already?
ps ill post a pic of my board

http://memimage.cardomain.net/member_images/8/web/2204000-2204999/2204493_30_full.jpg

http://memimage.cardomain.net/member_images/8/web/2204000-2204999/2204493_31_full.jpg

Worse to worse, you could use an aftermarket speedo for the time being.

Here is a little better price, $240:

https://www.autohausaz.com/search/product.aspx?sid=5wt21uemdda4yzelonuntjqq&makeid=800003@BMW&modelid=1012565@635CSI&year=1986&cid=18@Electrical%20%26%20Vacuum&gid=4529@SI%20Board

Apparently, 12/85 is the change over date between the separate SI board and the single board like you show. However, my '87 has different batteries in a different location.

Were the tach/speedo bad before replacing the batteries, or stop working after installation?

http://bigcoupe.com/ims/pic.php?u=21GvpX2&i=222 (http://bigcoupe.com/ims/pic.php?u=21GvpX2&i=222)

My batteries were 3 volt lithium, what were yours?

well i got the car passed down to me about a year ago and quickly got it driveable , the tach was cuting in and out at first the stoped working and would some times kick in then cut out , then towards the end of the summer the spedo started bouncing every once in a while , this whole time the si lights were acting eractic, so i did some research and figured it was the batteries . . . . . . .

batteries were 1.2v ni-cad

so basicly i figure the boards shot when i put it in i couldnt test the speedo tho just the tach , i had no steering wheel and the gas and temp gauge did budge and i know i must have a 1/2 tank and i let the car run a bit, i soldered the batteries in myself thinking if the was the cure id save the money on the board but apparently im going to have to buy the damb thing , biggest piss off is i fucked up the needle on the speedo (didn't have a work bench so i used the futon) in the process

im thinking or replacing the sensors for the speedo and tach just to rule them out they could be kickin in an out intermitently, plus there original anyway