What is the voltage output of an Apple 85W MagSafe 2 model A1424 without a load?

I believe these are smart chargers, and initially only supply about 3 volts in order to power a power management chip inside the device to be charged. Once powered by the 3 volts, the power management chip inside the device then communicates with the charger verifying that the device is compatible to be charged, and if that fact is verified, only then will the charger output full charge voltage.

Additional info provided by @MarcWilson.

Based on the answers to this question the supply doesn't communicate with a power management chip - it simply looks for a resistance of approximately 40 kΩ between its output and ground, and if this is detected then the full output voltage is enabled.

Also based on the above answers, if you often measure 0.2 V rather than 3 V then an intermittent fault in the cable seems most likely.