one hell of a tach problem

[Klits562]

this is for my friend He has a 90 hatch.He did a twin cam swap i think its an s14 ka24de.After the swap his tach of course didnt work so he bought a dohc cluster and that didnt change anything.So today we put his sohc cluster back in and tried the sohc to dohc write up on nico. We cut the yellow w/red stripe wire on the plug behind the cluster and we ran a wire from the plug to the ignition coil but we couldn't find the positive wire. He tried the black w/red stripe wire that he thought was the positive but car wouldnt start so we put the black wire back together and he tried another wire but idk what wire it was. that didnt work either.So he decided to run the wire to the ecu instead. He connected yellow w/red from the plug to the yellow w/red on the ecu and even that didnt work.Were completely stumped and have no clue what else it could be.

Cliff notes1.tach doesnt work sohc to dohc motor swap.2.swapped to dohc cluster that didnt work.3. swapped sohc cluster back in and did the sohc to dohc wiring from the nico write up didnt work.4. ran wire from plug on cluster to same colored wire on ecu(yellow w/red) didnt work either.

I suggested that he change the sub harness for the cluster from sohc to dohc but our junkyard that we go to said thats not whats wrong with it. Any suggestions?
Modified by Klits562 at 8:04 PM 10/5/2009

[Klits562]

come on someone help I've searched and i cant figure out wtf the problem is

[kikcaffine]

Plug a voltmeter lead into the wire comming off the ECU for the tach signal, it should be the under 6v setting when on the Multimeter. Make sure the car is running when you do it since its RPM based that increases the voltage. You should see the voltage of the wire start to increase as you rev it....

[rsagen]

check your wiring on your distrubutor, if that doesnt work, go get a cheap $25 aftermarket standalone tach from autozone. with the tach comes complete instructs to install it. on the distrubtor there should be a place marked "TACH" where the tach plugs into.

just my 3 cents

[snowboarder]

I just bought a 89 240sx with dohc motor. The digital HUD cluster SOHC tach didnt work. I wired my TAM to the ignition coil plug and it worked. This is how I did it.

Tools-Screw driversSplicerWire

1.) Pull out your cluster and find the yellow/red wire. If you can't find that then look behind cluster on the wiring board and it should say TAM on one of the cooper leads. There should be a screw attached to that lead. Follow that to the harness and that's your yellow/red wire. Now that you've located that wire we can move to the next step.

2.) Go to the engine bay and locate your ignition coil. The ignition coil has two plugs coming into it. One plug goes to your distributor and looks like a spark plug cable. IGNORE that. The other side is a 2 wire plug/harness. That's what your looking for. This is where it gets funny....The original dohc to sohc tutorial u followed says to splice into the positive. Well either I didn't splice into the right one or the tutorial is wrong but when I did this the first time it didnt work. A local mechanic told me that my tach should get signal from the negative of the coil and not the positive. Well basically what I did, was i tried both sides and one side worked.

3.) Once you've located the ignition coil harness and the TAM then you will need to connect them together with a wire. You have two options with the TAM side connection. You can wire it to the screw connected to the TAM cooper board lead. Or wire it to the actual yellow/red wire. (I screwed it in to the TAM screw on the board and snipped the yellow/red wire.) Then run that wire through your firewall to the ignition coil harness. Once you start your motor u should see your tach kick in. If you dont then try the other wire on the ignition coil. I know this is kinda ghetto but I GOT A WORKING TACH NOW!!!!

COST=0

[rsagen]

good job! now you can cut your tach wire to your computer lol and get rid of your governer (jk lol)