ATA 76

When DEECs are installed, sometimes the operating switch in the throttle quadrant (#12) for the ground bypass valve will have to be adjusted. This is because of the revised fuel scheduling in the DEEC. It can cause the ground valve to remain open when the engine speed is well above the 52% N1 speed cutoff due to actual throttle arm position. This will show up as a “BLEED AIR OVERPRESSURE” light or a large increase in airflow from the gaspers due to increased bleed air supply.
The easiest way we have found to adjust the switch position is to run the R/H engine and mark the throttle quadrant at 52% N1. Next, shutdown the engine. Remove the electrical connector from the valve (P348) and run a test lead from pin “A” to the cockpit. Move the switch until 28VDC is not present @ pin “A” with the throttle @ 52% position or greater.