Starter Won't Crank on Very Cold Weather

[DaVisionary]

Greetings, I am hoping someone might have run into this issue before and can provide any insight...

I noticed the explorer had a hard time starting on the cold, tested the battery and it was bad so I replaced it. Then after two days of not running, the explorer wouldn't start the morning. I thought I had a parasitic drain. Hooked up voltmeter, and verified there was no drain after modules went to sleep, about 45min - hour. Reading was right around .01 milliamps. I thought perhaps I had left something on, so I recharged the battery and dismissed it. Recently when we had below freezing weather the car would not start even when hooked up to a jump starter. (ran fine night before). Tried to manually jump the starter motor by using a screw driver and touching the positive terminal on the solenoid to the starter, and I heard a constant whirring from the solenoid/starter instead of the usual cranking sound. Next morning temps where above 30 degrees, car started just fine.

So I think I isolated the problem to the starter/solenoid, the starter relay and everything in between. Ordered a starter and plan on swapping it in the next few days. Does anyone know what would be failing under cold weather?

Thanks in advance.

 

[Boomyal]

Sounds like you made the right diagnosis.