As I said, a resistance in the range of 20 to 50 ohm is normal. Since you measured 40 ohm, it is ok and it shows your solenoid is NOT latching type (i.e. your solenoid is non-latching type). At any rate, as I suggested, you should measure voltages after solenoids are disconnected — so the resistance of the solenoids doesn’t matter in that case. When a zone is turned on, the voltage between COM to that zone port should be slightly lower than the input voltage. If not, I suggest that you submit a support ticket — a zone, when turned on, should output the input voltage minus a couple of volts; if not, I can’t explain it, and it’s best if you send it back to us for checking.