Had several problems with cooling system on my 86. Changed radiator, clutch and thermostat, still had problems, turned out that new radiator was defective. Changed it again, now temp is fine. All along aux fan was working properly. Today, however, had car running for 10 minutes with A/C on, sitting in front of house, got in and saw gauge was almost near red! Got out and noticed aux fan did not turn on! What do I check with this problem? Getting frustrated!