One way of checking for intermittent opens in signal or power wires is to use a load light at the plug that connects to the failed unit.
First of all, it will prove if a wire can handle the amperage load. Second, it gives you a visual indication of wire integrity while shaking down the wire bundle(s) that it runs through.
In this case, we had a 767-200 with a year long history of Thrust Reverser failures. This is a hydraulically driven system. It requires that the Isolation Valve in the pylon and two Sync Locks at the bottom of the engine have 28 VDC to operate. Lifting the T/R handle in the cockpit provided this power.
We opened some wing underside panels along with a top side panel above the pylon. We shook down everything we could get or hands on.
At no time did any lights flicker. No fix this time, but we've had luck using this method in the past.
During the APU engine start, the IGV (Inlet Guide Vanes) are supposed to be closed. This allows all incoming air to be directed into the combustion chamber. After start with a air demand (main engine start or air conditioning pack operation), the IGV vanes open allowing bleed air output.
