Correct. On the 2010 Express Van, the ground is Pulse Width Modulated through the ECM. This is how fan duty cycle is controlled.
Since there are variations in clutch wiring colors (OEM, AC Delco, others), best way to identify wiring is via connector pin assignments (A through E) as shown in...
Here are the wire assignments from A (left) to E (right) based on your first photo:
A and B control the fan.
C, D and E is for the speed sensor.
Connector Pins
A. Fan PWM ground
B. Fan hot
C. Low reference
D. Signal (speed) hall effect sensor
E. +5V reference
Well, since I discovered this thread about 1 1/2 years ago, I finally completed my switchover to an EV clutch about four months ago and I do have to say, I'm extremely impressed with the performance so far. The thermo clutches just did not react fast enough under very heavy loads and an...