5V VAC? Or do you mean 5V DC? Do you have a 5V AC transformer or where is it coming from?
The LED is a power indicator, it is not for showing station status, it merely indicates the 5V line is available.
COM is connected to one of the 24VAC wires. If you don’t provide AC voltage to the 24VAC in terminal,, there won’t be any voltage output. 5V is only used for signal logic, it is not used to power the sprinkler solenoids.