I was making a software change to filter the input signal because some cars seem to have noise on that line even when you turn the engine off, the fans keep running. Well I put that software change into one unit and will send that unit off to see if it fixes that problem in that car.
Anyway, I ran across a software bug that could cause the fans not to go on. It's a rare occurrence but I don't want anyone to have that problem. So I recommend you remove my solid state fan relay (painted brown) and use a standard mechanical relay until you send the solid state one back for a software update.
The problem can happen when one signal (the AC or otterstat) turns off and the other one turns on within 1 or 2 seconds of the first one turning off.
Sorry about this inconvenience.