Problem with A/C Request on DI6, series 6 RX7

[Pete_89t2]

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!

[Adamw]

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.

 

[Pete_89t2]

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.