Trinary switch install help

[Mayfield]

I have a 85 c10 with factory ac. I swapped a 5.3 4l60e from a 06 silverado last year. Trying to get my ac wrapped up before the summer heat kicks in.

I changed all the components out for new ones, except for the compressor that came with the 5.3. I'm running electric fans, that are pcm controlled. I installed a separate ground signal Relay for the trinary switch to turn on the secondary fan when pressure gets to high.
I mounted the trinary switch on the side of the drier where my binary switch was. I wired the switch up according to VA diagram. Simple & straightforward.

My problem is the switch does not seem to be working properly. The system is charged, compressor kicks in but the fan does not kick on or the compressor did not kick out when pressure got to high, blew a line. So I replaced the line, charged it back up, grounded the fan wires so the fan would run. Ac is nice and cold and pressure is stabilized.

So from what I have read, I can mount this switch on the drier, but that is the low pressure side, it will never reach enough pressure to kick the fan on or the compressor off right?
If this is the case, where are you mounting the trinary switch?
Or, is it possible I just have a bad switch? Any insight would be greatly appreciated.