Ive got some A/C problems....

car 1: rapidly on/off alternating about every 5-10 seconds. Just had a refill.

car 2: Checked the coupling and it engages when power is applied (when its out of the car). But when its in the car it wont engage. System is empty as when I went for a refill, they emptied it again because it was not working.
Checked the sensor on the compressor itself and was fine.

I also cannot find checking procedures of the transistor/resistor that sits under the dashboard inside the blower housing.
regulyator-skorosti-motora-otopitelya-mitsubishi-legnum-ec5w-6a13-1_96.jpg

Do we have a A/C controler / ecu, or is this the A/C unit in the dashboard itself?

Any other tips that I can check?