I have a Haltech Elite 1500 on my car and it looks like, by default, Haltech has the tacho connected to an digital pulsed output (DPO) configured as 8v pull-up in the NSP software. This has been working fine on my car, but I'm looking to see if I can free up the variable pull-up DPO. Does anyone know if the tacho input (I believe referred to as TAM in other threads) will work with a 12v pull-up DPO?

Since I'm looking to free up a 5v pull-up DPO, I also noticed that the thermo fans relay is connected to a 5v pull-up DPO. Anyone know if this relay would operate as expected if connect to a 12v pull-up DPO instead?

Appreciate the help.

 

I'm not sure about the Haltech side of things, but AEM ECUs use internal 12V pullup resistors for the tachometer output and that has worked with the tacho on my 1994 RX7 for 15+ years. For the fan trigger, the ECU driver doesn't need any internal pullup since the relay coil is receiving 12V to make it work. Be sure the ECU driver with 5V pullup can tolerate that the relay has 12V powering it, but that's a very common circuit so hopefully the Haltech can work with that.

 

Looking at this: https://www.rx7club.com/interior-ext.../#post12212569 and the 2 following posts you should be be perfectly OK feeding TAM from a12 V pullup output, short and long term.