Hi all,

I'm working on a '73 K20 with an L83 and ECU out of a 2017 Silverado 1500. I've installed two discrete Spal fans on two relays and wired both relays to be triggered by X1 pin 59 on the factory '17 ECU, and set up the calibration like any other discrete fan setup I've run before. The issue is I don't see the ECU actually trigger the fan output in VCM Scanner, and no matter what, with that calibration, I have 3V at the fan output pin. I switched it back to PWM in the tune to verify the ECU output wasn't fried, and I was going to let the relays buzz for a little bit just to make sure it was working as expected. With it configured like that, I see the fan output PID actually change in VCM Scanner, and the relays turn on normally at the target temperature, no buzzing! The issue I have now is that they don't shut off once it cools, even after the ECU sees some vehicle speed.

Any help would be appreciated. I've attached tunes and logs from the discrete and PWM configurations.

KinnardK20_ConfiguredFanOutput5_Discrete.hpt
Fan5Log1.hpl
KinnardK20_ConfiguredFanOutput8_PWM.hpt
Fan8_TestDrive_FansStuckOn.hpl