I was hoping someone can help me with this. I'm trying to replace a heater/AC control unit in an older car. The mode doors are controlled by 2 12v actuators. the 1st has 2 positions the second 4. They operate by applying 12v+ to the terminals. Giving me a total of 6 to power on and off. I don't need to reverse or control speed, just turn on and off. I've checked the load on both and the Max. was 3.5A. So far I have looked at H-bridge setups and get more confused with every link or post I read. Basically all I need is the 74HC_HCT595 shift register I'm using to act as a switch to control the mode doors. I know I can use relays but I'm trying to avoid that if possible. Reason being 6 outputs for mode doors, 4 for blower control, 1 AC power relay, 1 AC clutch, and so on. Really didn't want a box of 12 plus relays that are prone to failure in the given environment.
Sounds like you need an array of Darlingtons or MOSFETs? You only need H-bridge if you need to reverse the polarity of the motor supply.