Alternator Problems

My 73 Valiant has a on off type problem that only happend in the colder weather. I will start it up and all is fine good voltage regulator fine. After driving for some timee never the same the regulator kicks off and I am running on battery only. 5 to 7 mile down the road the regulator alll of a sudden pops back on all is well again. This is a problem driving in the dark and winter here in Wisconsin at 5:30 AM. have checked all the wires and cleaned all the contacts and the grounds. Had the alternator checked and all shows fine,even put another one on and same issue?? Any help would be great.