RPMS read only when cold?!

[ChachiS13]

I posted this somewhere else but figured this is best spot to ask

Heres my setup:

1990 240SX with SOHC ClusterBlacktop SR with E5 ECUApexi AVC-R

Ok, installed my AVC-R and it will only read RPM's when car is first started. Before my instalation of the AVC-R I have never had a way of reading RPMs in my car so I dont know if the problem is new

Once car is at operating temp, the RPMs start flickering random numbers until it eventually just reads 0 RPM

If I shut car off and let it cool off for a sec, it will start reading again then shut off after a couple seconds. So Ive come to the conclusion that this happens when something gets heated.

Any ideas?

[ETTInnov04]

Why are you still running the SOHC tach? As for your AVC-R are you sure you tapped into the correct wire? I know it sounds stupid but a lot of time you spend most of your time trying to figure out the stupid problems.

[ChachiS13]

Im running the SOHC tach cause I ran out of money and not having a tach was the least of my problems cause I was gonna install the AVC-R which has a tach reading

Im sure I connected it to the right wire. Im using the Apexi Diagram and it is the yellow/red stripe wire on the ECU. Also it reads RPMs perfect when its working, but then dies away. Its real frustrating. Im gonna swap ECU's with someone and see if maybe the ECU just goes wierd when it heats up, but I doubt it