Narrative:

Prior to departure; the right pack was deferred due to a repeat write up that I had made indicating that the pack inoperative light and associated right pack off EICAS did not illuminate when the pack is selected off. We had been flying this aircraft all week so we were familiar with this particular issue. There is nothing wrong with the pack and there is nothing wrong with the light indicating the pack is off...there is something wrong with the pack controller or a sending unit which sends the signal to the pack light and EICAS.this had been discussed at length with several maintainers over the course of the week since this was a repeat discrepancy. Pack deferral requires fwd cargo a/C switch to be placed in the off position. In cruise at FL350 about 30 minutes prior to top of descent; fwd eqpt ovht EICAS illuminated. Followed QRH. Stby position of equipment cooling selector failed to resolve the ovht at the expiration of required five minute waiting period. Selected ovrd. Avionics began to fail. First officer wxr fail illuminated followed shortly thereafter by capt. HSI fading to black. Flight deck temp indicated 33 degrees C.due to night flight near convective activity and need for radar displays; beginning of loss of capt ADI; and potential to lose all avionics; I elected to re-engage the fwd cargo a/C and turn on the (deferred) right pack. Avionics displays immediately returned to normal and we continued the short flight to destination uneventfully. No emergency [stated with ATC].

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Original NASA ASRS Text

Title: B767-300 flight crew endured one pack operation in hot weather resulting in degraded avionics. System was restored to normal configuration.

Narrative: Prior to departure; the right pack was deferred due to a repeat write up that I had made indicating that the pack inoperative light and associated R PACK OFF EICAS did not illuminate when the pack is selected off. We had been flying this aircraft all week so we were familiar with this particular issue. There is nothing wrong with the pack and there is nothing wrong with the light indicating the pack is off...there is something wrong with the pack controller or a sending unit which sends the signal to the pack light and EICAS.This had been discussed at length with several maintainers over the course of the week since this was a repeat discrepancy. Pack deferral requires FWD Cargo A/C switch to be placed in the OFF position. In cruise at FL350 about 30 minutes prior to top of descent; FWD EQPT OVHT EICAS illuminated. Followed QRH. STBY position of equipment cooling selector failed to resolve the OVHT at the expiration of required five minute waiting period. Selected OVRD. Avionics began to fail. First Officer WXR FAIL illuminated followed shortly thereafter by Capt. HSI fading to black. Flight deck temp indicated 33 degrees C.Due to night flight near convective activity and need for radar displays; beginning of loss of Capt ADI; and potential to lose all avionics; I elected to re-engage the FWD Cargo A/C and turn on the (deferred) right pack. Avionics displays immediately returned to normal and we continued the short flight to destination uneventfully. No emergency [stated with ATC].

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.