Radiator fans do not turn on. 12V feed directly to fan will make the fan operate on 1999 Cadillac DeVille

So the fans check out I also tested the 3 Relays under the fans, check out ok too. Fans will also work if the air conditioner compressor is on. But not under normal driving with Air conditioner off. The car starts to over heat until it is moving then the temp comes down rather quickly. The fan circuit has a problem. So tracing back what’s next? So far I checked the fans, tested OK. Then tested each relay, tested OK. What feeds the primary circuit to the relays?

by in Castro Valley, CA on December 03, 2012
3 answers 1 comment
ANSWER by on December 03, 2012
Can't beat a GOOD scanner when checking these out!
ANSWER by on December 03, 2012
May have multiple sensors/switches for that car. Need to know circuit for fan controls to start. Coolant temp sensor , or rad. fan switch, Some cars have them seperate , others combined . Need to know which you have , then you can test properly.In the meantime--when you come to a stop , turn on the A/C or defrost.
COMMENT by on December 04, 2012
Thank You, I will investigate futher :-)
ANSWER by on December 04, 2012
agree with ziptie. get a diag and est so as to not waste time and $