96 JXA cooling fan won't start HELP

My JXI conv. Sebring's cooling fan starts 2% of the times it should. The car doesn't overheat if it is moving but does in a stop and go traffic (and I live in LA) so there's a lot of that. How should I strart narrowing down the causes? I have a repair manual for the car so I can probably change whatever needs to be changed if I knew where to start. Please help, I have no other means of transportation.

Thanks,