Toyota: 91 Camry LE... Strange radio/electricity problem??

I have a 91 Camry LE and have had unusual problems with my radio. It
is one of the larger radio/cassette player combinations. It has a
square LED display. I have had continuing problems with the radio
"cutting out" as I drive. I have had it repaired at an outfit that
specializes in auto radios and it worked for about 5 months after the
repair. Last Spring, it started with the same problem again.

Here is the strange part, now that I am in the throes of a typical
Houston area summer, the radio plays like a charm as long as I am
running my ac and the associated fan. It is as if the additional
electrical draw causes my radio to work correctly. I would like to
know what the possibilities are so that it will work all year round.

Thanks, Al Kondo