Tach Help!!! (I'm an f'in idiot)

#1

Well, another lunch hour at work trying to get something done on the car without taking weekend time away from the family gets me into serious trouble! What’s the one electronic thing on the car that’s really helpful on-track? That’s right, the tachometer. Now I don’t have one.

As one of my other threads alluded to, I’ve got this German who wants my cruise control. I don’t need it, so his silly money is an incentive to me. At lunch I went to remove the wiring harness from the car. I had already disconnected the servo and the wiring harness from the cruise control ECU. Today I removed the switch on the column, removed the switch on the clutch, and unplugged a ground underneath the panel that went to the bundle. One thing held me back–a blue and yellow wire to the back of the instruments. I cut this. Now my tachometer doesn’t work! Is this wire the culprit, and does anyone know what I need to splice it to? Tracing this wire it appears to go to the harness for the ECU, so it’s difficult for me to imagine how cutting it disrupted some circuit since the tack worked without the harness plugged in.

I also took a big wad of wires that went over the steering column to the radio. I had an after-market unit, so the wiring harness had been messed with before. I cut out a giant bundle of wires, but none went up to the cluster. I also pulled a bunch of wires out from above the steering column, some rather forcefully, so it’s possible I also dislodged something.

Thanks for any advice,

Sasha the Idiot

Post edited by: Ex36, at: 2006/03/03 14:12

Post edited by: Ex36, at: 2006/03/03 20:31

#2

Tach signal is a yellow/white wire that comes from the ECU.

#3

I see the reference to the yellow/white wire in my Bentley. Thing is, I didn’t touch the ECU or its wiring. I’ve also discovered that the blue/yellow wire I did cut is apparently sending a speed siganl from the cluster to the cruise ECU, so this doesn’t seem like a likely culprit for the tach not working. Since I’ve also noticed that the OBC gets an engine speed signal, and it, too, is no longer working after my butchering, I’m beginning to wonder if these two are related?

Sasha

#4

One more clue: today I noticed that the fuel economy meter is not working either. So, the OBC, the fuel economy meter, and the tach are all out.

Sasha

#5

Did you lose a ground somewhere?

#6

I figured it out. As I said in the original subject, I’m an idiot. After reading a bunch of the Bentley it hit me like a ton of bricks: the tach, fuel economy meter, and OBC all share a fuse, specifically the 7.5 Amp #21. After buying a new one, all seems to be fine! Thanks for your input.

Sasha

#7

I had the same problem after I got my car back from Chris Schimmel. The tach was not working so after spending about an hour looking upside down under the dash I checked the fuses and had two blown #7 and #21. Works fine now.

#8

Glad you fixed it man. Just hope the fuse was blown during the rewiring!
Ed

#9

I’m guessing the fuse was blown when I grabbed a huge bundle of wires and went snip with a wire cutter. And to think I had derided others for "thinning" out their wiring! Just shows how desperate I was to make some dough–$100 for all 6 speakers, the cruise ECU, and the cruise wiring harness. I almost have enough to finish my build. It’s funny that I’ll have a complete car, and no money for track time, while I know others who are taking their car that’s far from finished to the track every month.

Sasha

#10

OK, I’m going to revive this thread…

I have a German as well, who wanted the COMPLETE Cruise Control system, wiring harness and switches, you name it - I got the motor running today after having it out for a reseal/cleanup, etc. and I noticed the tach isnt working.

I checked the fuse box, admittedly, I do not know which one is for the tach but I found nothing blown.

I’ll recheck later tonight seeing that you guys say it’s fuse #7 and/or #21 - but if it’s not the fuse, what else could it be?

For reference, I REMOVED the plug, intact, from the rear of the instrument cluster that provides the speed signal to the CC ECU, I did NOT cut the wires…so do I need to put the plug back and snip the wires for some reason?

Again, I need to check my work over with a fine-toothed comb - but would like to know if anyone else has an idea of what else to look for. I will double-check the fuse box later tonight.

SEE YOU ALL AT CMP IN 5 DAYS…those that are planning to be there, anyway. :slight_smile:

#11

Tach is #10 and #21.

#12

That did it, thanks guys, you are da schizznit! :laugh:

I had briefly scanned over the fuses earlier but fuse #21 was the culprit, it was a “late-style” fuse that can’t be easily viewed through the blue tinted fuse cover, most of the others are the old style fuse where the element is exposed/visible from the top.

So -1 for me…ya’all are more than welcome to make a crack at me next weekend. :stuck_out_tongue: