Fan doesn't spin with RAM, but does without.

I have a big problem. The CPU cooler on my Dell Latitude E6420 is not working anymore. Just no life in it. I did some troubleshooting and realized when the RAM is removed, it takes a few seconds and then the fan goes to full speed. That should rule out the fan being faulty.
As soon as RAM is inserted into the machine, nothing. As if the fan was dead.

Any ideas?