Pete_89t2 Posted July 17, 2020 Report Share Posted July 17, 2020 Hi, I've got a wired in G4+ Fury in my FD, and I'm attempting to use DI6 as the "A/C Request" function. Long story short, it's not working as expected but I think I know why - voltage on the DI6 input is a bit higher than it should be when the AC is switched on, and that voltage varies depending on AC blower fan speed. Here's the voltages I measured on DI6, car not running but with a trickle charger connected to the battery: A/C switch & Fan Switch OFF: 12.4V A/C switch OFF, Fan switch set at ANY speed: 12.4V A/C switch ON, Fan speed 1: 1.51V A/C switch ON, Fan speed 2: 2.16V A/C switch ON, Fan speed 3: 3.36V A/C switch ON, Fan speed 4: 3.14V What is the recommended work around for this? A relay would work, but would be a bit more difficult to physically wire, so I was thinking a few diodes in series to drop the voltage input to DI6 would be a better/easier solution. Question is what is the voltage threshold for the DI, and how many series diodes would I need to reliably pull the voltage down enough? Thanks! Quote Link to comment Share on other sites More sharing options...
Adamw Posted July 17, 2020 Report Share Posted July 17, 2020 Yes, it needs to be above 1.5V for one state and below 1.0V for the other state. So you need to get all the "ON" voltages lower. 4 diodes in series should do it. On our S6 plug-in the AC Request signal uses a 2.4V zener diode (backwards) and a weak path to ground, as below. But my diode theory is not strong enough to say this will work for your voltages - so use at your own risk. Our notes say on the S6 the AC request signal varies between 1.5 & 2.6V depending on fan speed so yours is a little different. Quote Link to comment Share on other sites More sharing options...
Pete_89t2 Posted July 17, 2020 Author Report Share Posted July 17, 2020 6 hours ago, Adamw said: Yes, it needs to be above 1.5V for one state and below 1.0V for the other state. So you need to get all the "ON" voltages lower. 4 diodes in series should do it. On our S6 plug-in the AC Request signal uses a 2.4V zener diode (backwards) and a weak path to ground, as below. But my diode theory is not strong enough to say this will work for your voltages - so use at your own risk. Our notes say on the S6 the AC request signal varies between 1.5 & 2.6V depending on fan speed so yours is a little different. Thanks, I didn't think of using a Zener diode & pull down resistor but that's a neat solution. Though the 4x series diodes should be physically easier to add inline to my wiring harness at this point. Quote Link to comment Share on other sites More sharing options...
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