12v orig sensor signal to 5V sensor signal | FerrariChat

12v orig sensor signal to 5V sensor signal

Discussion in '308/328' started by DanielGA, Jun 30, 2025.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

  1. DanielGA

    DanielGA Karting

    Mar 19, 2018
    144
    Midwest
    Full Name:
    Daniel A.
    All,

    I am converting my Mondial/308 engine to a modern ECU.

    The oil temp + oil pressure sensor original to engine are single-wire and 12volt I presume. This means ground is the chassis and 12v signal comes from the gauge...so as the sensor varies the resistance the gauge displays different values based on the voltage from 0-12v. This is my understanding.

    The AEM ECU I am using, like most ECUs today, supports 0-5V signals. How do I connect the 12v sensor to it?

    I think the solution is a pull-down resistor circuit (two resistors in fact) so that I can still feed the gauge but also produce a 5V signal. Anybody have experience with this?
     
  2. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,711
    The twilight zone
    Full Name:
    Help me get this thing finished! https://gofund.me/39def36c
    Not a pull down resistor, a voltage divider and make sure the resistors are pretty high value compared to the the resistance of the sensors so it doesn't affect the gauge readings. I have an AEM in my car and have the oil temp connected this way.....I don't recall what resistors I used and I'm sure they are heat shrinked so I can't just look, I can maybe ohm them. But like sensor>200k>ECU>100k>gnd (use the ECU sensor gnd) will convert 12 (13,8 when the alternator is on) to 4 (or 4.6). I'm 3/4 remembering the the gauge is sending 8V to the sensors though, so 100k>ecu>100k> gnd to make it 4V Is what I think I did so I only needed to buy 1 pack of resistors.


    I'm surprised you're installing an AEM as they are obsolete since holley bought them out....and made me very sad
     
  3. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,711
    The twilight zone
    Full Name:
    Help me get this thing finished! https://gofund.me/39def36c
    I guess the question I have is... where's the build thread? I'd love to see what you're building :)
     
    26street and flyngti like this.

Share This Page