'86 740 GLE speedometer/tachometer

It's easy to put the tach wire on in the wrong place. If you do, then you can ground the ignition signal, which results in no start. Sounds like you still have the tach wire in the wrong place, just not as wrong. The speedometer power, ground and signal are all connected in the one 3 or 4 pin plug that connects on the bottom edge of the speedo, so it's hard to connect in such a way as to kill the sender. However, it's not the greatest system, so the connections can be poor.

I figured out what I did. I went to the junkyard and got another cluster, there are 2 connections at the top of the speedometer. When I took the cluster apart I put the 2 wire on the wrong side. I really screwed up. So something is definately fried, just don't know what yet. It's obviously whatever connects to the other end of those 2 wires, just don't know what yet. Maybe the speedo sending unit. Any ideas?

I figured out what I did. I went to the junkyard and got another cluster, there are 2 connections at the top of the speedometer. When I took the cluster apart I put the 2 wire on the wrong side. I really screwed up. So something is definately fried, just don't know what yet. It's obviously whatever connects to the other end of those 2 wires, just don't know what yet. Maybe the speedo sending unit. Any ideas?

I figured out what I did. I went to the junkyard and got another cluster, there are 2 connections at the top of the speedometer. When I took the cluster apart I put the 2 wire on the wrong side. I really screwed up. So something is definately fried, just don't know what yet. It's obviously whatever connects to the other end of those 2 wires, just don't know what yet. Maybe the speedo sending unit. Any ideas?

Did you blow the fuse?

Checked all the fuses in the dash. When I hook up the wire on the back of the speedo the car stalls, it won't even start when it's hooked up. I disconnect the wire and it starts and runs fine.