Anyone willing to help me w.speedo problem?

I've posted a few threads between Tech and 328 forums about my speedo failure. I've established that the speedo and drive unit are fine so there's a wiring/connection problem somewhere, and I suspect it's between the passenger footwell and another connection I can't locate. Problem is, my electrical skills are rudimentary, and while I have a wiring diagram I'm unable to physically trace the routing of the wire from the sensor to the head so I can test connections.

Is there anyone relatively local that has the ability and willingness to spend a couple hours with me trying to locate where the problem is? I'll buy you lunch or a case of beer! I know I'm close to figuring this out but now I'm stuck!

Thanks

 

ability? yes.
willingness? no. not for lunch or beer.

 

Well that's all I'm offering. But thanks for the pointless reply

 

Dave is it possible to run a few wires from the sending unit to the speedo head and test it out. Even if you run the wires outside the car . Also check from the speedo head to the fuse block (pull fuse). Then from the fuse block to the sensor. If you are not blowing fuses then you either have a connector problem (need to clean all connector pins/sockets) or a intermittent short (or broken) sense wire. I would bet this is the problem. So if you run a new sense wire from the sensor to the head (direct) and it works then instead of finding the bad wire I would leave the replacement in.

 

Steve, thanks for the suggestions. I spent some time yesterday pulling the related connector behind the pass. footwell and testing the harness' two wires (RN & the other one, white striped green). One of the wires tested ok w.the ohmeter (got audio conf) but the other I only got a numerical read which was strange. So I think you're right that there's a short in the wire between the sensor connection and the 1st (moving twds the head) connector behind the pass. footwell.

I am going to run long wires to test from the sensor to the head today.

 

OK good luck and keep us posted. Although I didn't have this problem with my Fcar I did have a similar problem with my wife's Volvo. They have a sending unit mounted in the rear differential. She was getting an intermittent speedo and it was cause by a bad sensor wire. I ran a new one and it worked.

 

I had a friend who's an electrician come by yesterday. He's not a car mechanic but at least he understand electronics and circuits better than I and seems to know how to come at this from an elimination standpoint so he's digesting the wiring dgm and we'll get back into it over the wkend.

I did try running long wires from the sensor to the connection under the dash (since I didn't feel like the rigmorale of removing the gauge cluster AND deducing that since the speedo bench tested ok I could just go to that connector - kind of a cheap quick attempt I guess) but got nothing. My buddy seemed to question whether that would tell us anything as - he thought - we were only testing one side of the circuit. I think his conclusion as of yesterday was he needed to figure out where the other wire routes since it appears to run amok and hit lots of things. Anyway he seemed to have a methodical approach to how we'll trace it down so it's more than I can do.

Looking at the relay block we discovered that the unit for the headlight motor was not pushed all the way in - but the lights have been raising/stowing properly so it didn't seem relevant. I note this since the speedo routing runs through that relay it seems so, remembering a moment when the speedo was still intermittently working when I turned on the lights and there was an immediate (but perhaps coincidental) speedo affect (i.e. it jumped to life) I was hopeful that somehow pushing the relay in would be the problem. It didn't make sense esp since the lights came up, down, but what the hell - electrical issues can be mysterious.

BTW after all the hours I've spent on this by now I'd be happy to bring it to my wrench but he's 2 months backlogged, but graciously willing to talk me through as much as he can over the phone.

 

Fixed http://www.ferrarichat.com/forum/showpost.php?p=137756684&postcount=15