1989 240sx hatch, rb20det - tach issues

[Acecool]

Ok, I have an SOHC previously auto 240sx.

I have an aftermarket tach connected to pin 7 on ecu, power and ground from cigarette lighter = working perfectly.

I had my SR tach (7.5k red line, 9k limit) calibrated by Carl H, he says its working perfectly. I plug it into my cluster where I am getting 14v at IGN, 5.45v at TAM (decreasing in voltage as I give gas), and the ground is grounded because I used that connection to test power with voltmeter (I checked off of the screws that you screw it in with).

The SR tach does not get any signal, needle doesnt move. The DOHC tach that I also have also doesnt get signal. The aftermarket one works perfectly.

I tested each of them individually, without having the aftermarket one plugged in. I also tried plugging the aftermarket one in after no signal was being received. I get nothing.. Any ideas guys? Both Carl and I are stumped as to why the needle isnt moving.

[Acecool]

Bump... anyone know?

[l0nestar]

Is there an obstruction in the plug? Is a trace grounding out possibly with the OE tachs, but not the aftermarket unit?
I'm thinking extraneously here..

[Acecool]

I dont have them both plugged in at the same time. If I do, the aftermarket still works.

The plug is fine on the back of the cluster, because I can trace the signal from the ecu, to the screw on the back of the tach without issues. The tach when the car is turned on seems like the needle is being pushed to 0rpm... more force is applied. When car is off, the needle can be "flicked" around easily...

Ground is good in the back of tach, IGN gives the proper voltage when car is on/off...


I looked in the R32 FSM, and I cant find anything for the RB20DE/T regarding pin 7 on the ecu however on the 25, 26 etc it says the wire goes to the TACH, AND IT ALSO GOES TO (V) then to GROUND. Do I need to ground the signal wire after putting it through something or what is that about?

[Acecool]

Bump...