'90 tach noise filter wiring

[tkelly27]

My tach give the faintest sign that it might work every so often. Reading up about it, I found the noise filter and it looked ok. However, I found that the previous owner decided it would be a good idea to chop all the wires and reconnect them. All 3 going into the harness have detached. They are all white, I have no idea what to do with them. Is there marking on them? Will I hurt something if I try all 9 combinations available to me? I have a multi meter, can I use that to figure it out?

 

[luv2rallye]

Yes you can damage something. The noise filter is just a resistor in series with a capacitor (other side of capacitor is connected to the case which is bolted to ground). With this knowledge and your meter, you can then tell which wire coming from the noise filter is what. One white goes from the junction of the resistor and capacitor to the tach (and A/T unit if you have it). The other side of the resistor has 2 white wires. One goes to ECU pin 109 (this wire is shielded along with the wire that goes to the tach). The other white wire also connected to this resistor side goes to ignition coil pin 3.