2 stage Fan control

I'm having trouble getting my 2 stage fan setup to work. I have it wired for the 2 speed/series 3 relay setup and I have added a trinary pressure switch to ground relay 1 for low speed during a/c operation. I've got terminal 42 on c1 blue controlling relay 1 and terminal 33 c2 red controlling relays 2 and 3 with the tune set to command 1 at 185*-283* and command 2 from 200*-283*. I can command the relays with VCM scanner and everything works as it should, fan 1 on gets me low speed on both fans and then fan 1 on with fan 2 on gets me high speed on both fans. During normal operation fan 1 control works as it should for low speed but I never get fan 2 control to automatically command the other 2 relays for high speed. I also noticed my fan 1 command on the scanner flickers on/off while being commanded but fan 2 never gets commanded. I'm hoping it is something simple in the tune. I've attached my tune file and a log. Thanks for any help!


1968 Chevelle swapped with
99 Silverado 5.3L with ecm and harness

It's the 99 OS. Efans work best on blue/red PCMS with a 02 OS.

Change your A/C > Hardware > Type Fitted to analog. Also the fan off temps need to be lower than the fan on temps.

Compare your fan settings to a stock 1999 F-Body, as there are some other settings to change for the A/C.

Russ Kemp