I bought a 2003 sprinter that had no response when the key was turned. Dash lights came on, and the engine cooling fan came on full blast. The previous owner had already replaced the faulty steering column fuse block which can cause this problem. So we had to dig deeper!

Info on this particular issue:
If you have this issue coupled with the cooling fan on full blast, it indicates an issue with the ECU (brain of the van). A communication failure with the ECU causes the van to go into a failsafe mode: blasting the cooling fan just in case the van is overheating (cause it doesn't know what the sensors are saying to the ECU).

Often the issue is in the fuse block on the bottom of the steering column- a problematic connection here interrupts communication with the ECU. Some people find that the issue remains once the fuse block is replaced. That was the case with my van. In this case, take a close look at the ECU (located under the dash to the left of the drivers seat). Look for any signs of corrosion, bent pins, missing pins, shake the ECU (there should be no rattling sounds).

Do you have this issue? What have you done to troubleshoot it?