A DHC8 FO REPORTS FLYING AN ACFT WITH BOTH THE ENG ADAPTER DOOR OPEN/CLOSE INDICATOR AND ENG INTAKE HEATER INOP. MAINT DID NOT VERIFY OPERATION EACH FLT.

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WHILE PREPARING FOR A FLT ON OR AROUND JUL; I WAS THE FO ON A FLT THAT RECEIVED A RELEASE INDICATING THAT THE ENG ADAPTER DOOR OPEN/CLOSE INDICATORS WERE INOP FOR THE #2 ENG. IN REVIEWING THAT MEL THE FLT CREW UNDERSTOOD IT TO MEAN THAT THE ENG INTAKE DOOR OP HAD TO BE VERIFIED BEFORE EACH FLT AND SEPARATELY THE ENG INTAKE HEATER HAD TO BE VERIFIED OP. WE VISUALLY CONFIRMED THE DOOR OP BUT DUE TO AIR TEMP ABOVE 15 DEGS CELSIUS IT WAS IMPOSSIBLE TO TEST THE HEATER FEATURE ON THE GND (IT TURNS ON AND OFF AUTOMATICALLY). AS WE WOULD NOT BE ENTERING ICING CONDITIONS WE THOUGHT IT MEANT IT WAS ACCEPTABLE TO CHK THAT IN THE AIR. WE PROCEEDED WITH THIS UNDERSTANDING. IT WAS LATER BROUGHT TO MY ATTN THAT THIS WAS NOT AN ACCEPTABLE METHOD AND THAT THE HEATER NEEDED TO BE CHKED BY MAINT PRIOR TO EACH LEG WHICH WE DID NOT DO. I FEEL THIS WAS DUE TO A LACK OF CLARITY IN THE MEL PROC; AND HAVING AN MEL THAT WAS NOT POSSIBLE FOR THE CREW TO ACCOMPLISH. CONTRIBUTING TO THIS WAS MY SIMPLY FOLLOWING THE CAPT'S INSTRUCTIONS AND NOT REVIEWING THE MEL PROC PERSONALLY.