Originally Posted by muttsjet
...., can a relay just go bad,
You should be able to get another one at Pep Boys or NAPA expecially if you take the bad one with you. Just test the new one before you put it in to make sure it's pinout is the same as the one you're replacing. You can put a 9V battery across the coil terminals and should hear it click. The other way to check the pinout is to look for the European terminal numbers 85, 86, 87, 87a and 30 as illustrated below. The relay coil is between 85 and 86; the fan current flows from 30 to either 87 or 87a:
BTW, just to make sure you don't get sidetracked by something: when the A/C is on
it can force one of the cooling fan relays on to guarantee air motion through the condensor even when the coolant is not hotter than the radiator fan trip temperature. I believe it is relay D that gets this treatment.
But in the scenario you describe, if the A/C is off
the two fans should definitely go on and off together, either via the dash switch or the thermo switch in the radiator.