84 m50 swap speedo not working through c3 or c6

[Rdreas]

IMG_20140729_001941 by Rdreas, on Flickr
As the title state I noticed when I was taking the car around the block that the speedometer wasn't working. Originally I had pin 14 of the x20 hooked to one of the green output pins on the cluster. Didn't work... So tonight I was doing some searching and found threads mentioning going through pin 26 of the yellow c3 connector on the back of the cluster. So then I thought maybe my car is just special so I went through the ETMs and am still stumped. I even thought it could be an issue because I also swapped in a 3.25 LSD. Checked both speed signal sensors I have and when the wheels turn the resistance comes and goes as it should. Could this be my SI board??
And just in case here are the etms for my car to save you some searching.
Screen Shot 2014-07-30 at 11.08.56 PM by Rdreas, on Flickr
and the c6 wire was blue/yellow.
Screen Shot 2014-07-30 at 11.09.56 PM by Rdreas, on Flickr
so then I tried the brown/red wire on the c3.. and still no luck
Any help would be much appreciated.
Car is an 84 325e with a m50tu swap from a 95 vert

[justin_l_]

Did it work before?

[Rdreas]

Did it work before?

I can't say for 100% sure bought the car with a dead m20 but I bought the cluster from an e30 shop near by... My tach works perfect and fuel works too.temp and econo gauges even jump a lil but speedo doesn't move..

[justin_l_]

Do you have access to another cluster you can try? There are a couple guys in Atlanta I believe. SI boards are common so it may be the issue. You should be able to check for a signal the the cluster with a multimeter. That would tell you if your getting a signal from the diff.

[Rdreas]

Do you have access to another cluster you can try? There are a couple guys in Atlanta I believe. SI boards are common so it may be the issue. You should be able to check for a signal the the cluster with a multimeter. That would tell you if your getting a signal from the diff.

I have my OG cluster but 5k tach.. when I was looking at Si boards last night they didn't say anything about speedometer though... Found a link about tracing it back to the cluster so I'm gonna try that tomorrow.

[justin_l_]

Could be a loose or dirty grounding nut on the back of the cluster.

[M3PO]

I have an 84 also. I also swapped to a newer cluster and I have a 3.25 LSD. My speedo has always worked with both clusters and both diffs. It is not related to the swap.

The only speedo related thing that needs to be addressed with the swap is sending the VSS signal to the ECU so you don't have a reduced rev limit.

[Gregs///M]

SI board has nothing to do with the speedometer circuit.

The brown/red wire from the rear diff runs to the C2 plug, pin 12. That is speed signal input. You are sending speed signal to an output, which doesnt make sense. The speedo needs speed signal in. Check the brown/red wire at C2 to verify you are getting pulsed signal there when wheels are spinning.

Double check fuse 10, 12, and 21 are working or the speedo will not work.

[Rdreas]

SI board has nothing to do with the speedometer circuit.

The brown/red wire from the rear diff runs to the C2 plug, pin 12. That is speed signal input. You are sending speed signal to an output, which doesnt make sense. The speedo needs speed signal in. Check the brown/red wire at C2 to verify you are getting pulsed signal there when wheels are spinning.

Double check fuse 10, 12, and 21 are working or the speedo will not work.

Thats what I thought, thanks for the confirmation. It makes since and now that I look at it, it's clearly marked signal in but isn't the signal going from the cluster out to the e36 ecu to tell it the speed? You honestly just made me take a harder look at that etm. Hopefully i can figure this out tomorrow, I've been slacking and i have to move the car out of its bay by next weekend.

[Rdreas]

So another few days slacking, but finally got it together today and played around some. checked continuity from the diff to the c2 and it was good so I swapped in my eta cluster it came with and gave it a try to see if my speedo was going bad. Still nothing, so I pulled my cluster out and took it apart but everything except my odometer gears looked good.
IMG_6331 by Rdreas, on Flickr
IMG_6332 by Rdreas, on Flickr
IMG_6333 by Rdreas, on Flickr
As always Help is much appreciated.
Thanks, Ryan.

[Rdreas]

The brown/red wire from the rear diff runs to the C2 plug, pin 12. That is speed signal input. You are sending speed signal to an output, which doesnt make sense. The speedo needs speed signal in. Check the brown/red wire at C2 to verify you are getting pulsed signal there when wheels are spinning.

Double check fuse 10, 12, and 21 are working or the speedo will not work.

Gotta say you solved my problem. I never checked my fuses because I had previously tested my entire fuse box and they were all good... So I completely missed the fact that fuse 12 was missing. Run to napa and put my speed signal wire to the input instead of the output and voila! Speedometer works! Can't believe I've let a missing fuse send me on such a wild goose chase oh well. Gregs///M if your ever in Atlanta I owe you a beer.

[2mAn]

So are you driving it now?