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Thread: tach wire location?

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Posts: 1-9 of 9
2013-02-08 18:00:27
tach wire location?
My tach is dead, and bought the car like that. Ive read every thread on here on dead/broke tachs and ended up changing out the cluster and ecu considering others members issues. Nothing, I also understand that the dizzy can cause this issu as well, I already have an extra just in case. What id like to do next is to see if theres a signal coming from the ecu like I should of done firstly but I dont know which wire to test and if there isnt a signal and possible harness damage how does one do a rewire?
2013-02-08 19:59:41
I know i seem impatient but is there a wire diagram available?
2013-02-08 20:31:16
There are wiring diagrams available. Check the Service Manuals section of the Manifesto.
Last edited by BenFenner on 2013-02-08 at 20-32-17.
2013-02-08 21:03:59
Well I pulled up the digital schematics for the digi cluster conversion but its for a b13, I have a b14. Im not sure where in that manifesto page to located thread that contains the wire im looking for. Im sure someone knows the color of the tach signal wire, anyone?
2013-02-08 21:13:37
It should be yellow.

It is one of only a few wires that connect to a (white?) plug under the radio area before going on to the cluster.
Last edited by BenFenner on 2013-02-08 at 21-14-45.
2013-02-09 00:08:13
Thanks I do appreciate you taking the time to help, but should I check the signal at the plug by the radio or by the back of cluster? If by any chance Does the wire continue to the dash as yellow? If you dont know its cool you helped enough as I didnt know there was a connector between the ecu and tach, ill check it out!
2013-02-09 03:34:33
Check it at the ECU. And keep checking down the line until you loose the signal. Although how you're checking for signal (oscilloscope?) is beyond me.
2013-02-09 15:39:25
Yeah ill just be checking for voltage rise with throttle by means of the multimeter. The car had a swap so its most likely a wire got pulled on, whats your theory on it being the dizzy, is that a common cause?
2013-02-09 16:09:20
First off, I don't think you can check the tach signal with a multimeter. I believe it is a PWM signal you'll need an oscilloscope to check.

As for the distributor thing, here are my thoughts on that.
The tach signal works like this... The engine turns the Cam Angle Sensor which sends a digital signal to the ECU for RPM. The ECU outputs an ignition signal to the coil (which goes on to feed the distributor, then the plugs) based on the RPM. Inside the ECU there is an inductive coil (or whatever circuitry) that picks up the signal to the coil. This in turn creates the signal for the tachometer and is output from the ECU. That means if for some crazy reason you're not getting a solid ignition signal to the coil then you can have issues with the tach. I don't see how a distributor could cause issues with the tach signal though. Sorry. And if the car is running really at all, then you should have a good tach signal.
Last edited by BenFenner on 2013-02-09 at 16-12-44.
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