DC to DC Converter

im facing an issue with DC to DC converters of C&D Technologies.

its about the failure of its output at either positive or negative terminal from regulated value(+12/-12 for 12v converter , and +15/-15 for 15v converter).

the output voltage drops to either zero or to level down the desired regulated voltage (it drops to 5 or 6V).

another mentionable point is that the output failure is only at one end either positive or negative, the other terminal operates properly.

if someone has used these converters, kindly share your experience or if someone gets the cause, inform it to me.

or if any new, more efficient DC to DC converter (that does not require an external fuse at input) is available, kindly inform me.

one more thing, the converter is placed on a circuit that has to be maintained at 60 degree centigarde temperature. im using industrial grade converter but still its facing the problem.

i think that the issue is because of the wrong selection of fuse and the other possible cause is continuous high temperature.

kindly elaborate the reasons in your opinion if you find them right or comment if you find them wrong.