Troubleshoot the Neutral
Outdoor lights won't light? Equipment won't run?
And it doesn't make any sense because the voltmeter says there is good voltage present?
Then troubleshoot the neutral. Sometime we forget it takes at least two wires to make a circuit.
If you read the necessary line voltage between hot and a ground but the equipment doesn't operate, check for a good neutral all the way back to the panel.
Especially in damp locations and outdoor circuits; be sure to check for loose wire nuts, loose terminals or corroded wires on the neutral side of the circuit as well as the 'hot' side.