The problem was when AC was turned on it triggered both fans simultaneously with no work around.
Alex2550 mentioned these PWM units in his build thread and while searching found quite an informative corvette forum post about controlling these with arduinos so thought I’d pick one up to try and I’m very pleased.
Normally it’s wired direct to the battery with big 10g wire and controls 2 fans. PWM control is then wired to your ecu for control. I didn’t need the PWM output so just terminated the output in the loom. There’s PWM Spal fans available now with this type of controller box built in but the Modular isn’t smart enough to control a PWM fan.
With this unit wired between the fan relay and fan, it simply ramps up fan speed when it receives power and ramps down when power is cut.
There’s plenty of reports on the net of these failing and tonnes of aftermarket knockoffs for $40 or thereabouts.
I started searching genuine part numbers that weren’t in the early years 2006-2010 range that had mass recalls and issues and found one for $100 on Amayama.
Figured for that plus a couple of $$ of connectors I’d give it a go.
Only wired it into the larger spal so incase it failed the other fan will still work. Also wired in connectors so I can just bypass the whole unit if needed.
There’s also no references on how much amperage these can handle and guesses are that huge draw or failing fans are the cause of death of these.
Normall they’re mounted to the back of the fan shroud for cooling but I couldn’t make it work so mounted it in the front of the airbox for max airflow through the headlight.
It’s quite cool watching the large spal come on slowly and steadily ramp up to full speed. Now I can have both fans and AC all come on at once with headlights and volts barely dip at all.
