Auto fan randomly working in 379 with Detroit 60

Checked voltages today.
5v at map sensor (boost)
0.83v at both coolant temp sensor and fuel temp sensor

Decided to swap the engine sensor harness and I'm getting the same readings. Idk what the coolant temp sensor should read for voltage honestly. Hopefully the harness did something, otherwise I'm sure it's be a bad ecm.

 

Swapped the engine harness. It did nothing.

Recently put new thermostats in and found out that I never had any in there. I really hate the previous owner.

Put a Horton fan switch in the thermostat housing. Doesn't turn on when it should. I'm going to put it next to the coolant temp sensor in the back of the head when I get home next. I think the thermostat housing never gets consistently hot enough to trigger it to open.

FYI the switch is NC 205 degree open and closes again at 194