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Discussion Starter #1
In the process of doing some troubleshooting and general tune-up/clean-up work, I had the ignition coil off my S3 to clean it up and also clean the terminals, and the contacts on the wiring harness that go to the coil terminals. After hooking everything back up, I have no movement of the tach. :( The only thing I can think of is that one point I heard one spark sound while I had the coil out, I assumed a contact had shorted to the body or another contact. How much voltage does the coil send to the tach? Could I have over-voltaged the thing if the lead going to the tach touched a positive lead somewhere?

On a not-really-related note, my fuel pump saga continues to deepen. Now I see that terminal #87 on the driver relay *does* get voltage with the ignition on....about half a volt. Whaaaa??? Even just putting 12 volts directly to the #87 lead at the drive relay only gives me half a volt on the line going to the fuel pump, like there's something in the circuit causing major resistance. And I hear a relay clicking up in the engine bay when I jumper #87 to a positive lead, but I've determined it's neither of the relays on the right front fender well and I don't see a relay anywhere else. Weird. I'm about ready to tear the car apart, rip out every last single shred of wiring, and put in a completely new harness. :p
 

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The coil sends a 12V pulse to the tach off the - terminal.

That deal with the terminal sounds like a nasty short or an incorrectly connected wire somewhere. (on a - where it should be + or vice-versa)

Either way, it needs to be located before it really hurts something, or better yet, starts an electrical fire.
 

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Discussion Starter #3
Well, I'm pretty sure it was one of the loose leads touching something it shouldn't have (it happened when I was moving stuff around down there and not paying attention to where the leads were), so not necessarily a fault anywhere. So it comes off the negative terminal of the coil, and it's the full 12 volts? Doesn't seem like it would be possible to fry it then.

Forgot to mention, I have four leads connected to the positive terminal and two connected to the negative, is this the right number? I was pretty sure I kept all the wires handy, and I checked several times and don't see any loose ones hanging around.
 

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my tach has intermittent failure. works fine sometimes and goes dead sometimes. i can find the sender for this at the coil? which wire is this in the engine bay?

TIA --guido
 

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from coil, negative terminal, in my Alfa it was white wire going from coil along radiator to the drivers side firewall (already with some other wires)
 
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