I have a mighty mule 572 gate opener it started to really struggle opening and closing the gate, I got a new arm under warranty replacement that still did not fix the problem. I checked my charging system, my batteries and power to the circuit board and all check out, what I did notice is the black and red wire (power wires) going to the arm only read 1.18 volts DC when activated, I assume this voltage should be 12 volts. What would cause this?
I am sorry to say that I would not be certain.
Anything on that board look damaged?
Also does that board directly power the arm? or does it run a relay?
-If so the 1.18VDC may be triggering that.
Excessive droop in the supply voltage to a device suggests a fault in the upstream supply system, such as might be caused by corroded connections, fractured wires, weak battery, or other such faults. I’d suggest measuring voltage directly across the battery terminals (not across wires connected to the terminals, the actual terminals themselves…) when operating and seeing to what extent it droops. It should measure approximately 12-13.5v without load, and not dip below maybe 10-ish under load.
Assuming that checks out, try looking for voltage drops in the supply connections under load. Connections and wires (ideally) are supposed to exhibit zero voltage drop under load, so the further from that ideal that reality is, the more problems one’s going to have.
The board seems to support dual arm configuration. Do you get same voltage reading if you connect the arm motor to the “SECONDARY” terminal? If not, then could suspect that the H-bridge FET(s) (Q1 to Q4) have got damaged.