[Richard]

you might think about a couple of things.

One, if there is a high resistance on the board between the incoming power and the outgoing to the compressor, not only would it result in a low amperage to the compressor, but the voltage going to the compressor would be reduced when the compressor was running. If you checked voltage at the compressor leads but without the compressor running, it would read the same as the incoming. Only under load would you detect a reduced voltage. If you look carefully at the board where the compressor plug is attached you will see two little gold colored dots. If you can get your probes on those dots, they are there for checking the board. Otherwise, you might can get your probes into the splices to measure voltage. If you do have a voltage drop on the board, the first place I would look is on the back to see if the circuitry is burned or compromised. The second likely culprit would be the compressor relay.

If the above test is inconclusive or not possible, I would switch the boards and see what happens.