I'm working on a 2004 Mercury Grand Marquis. The blower motor has suddenly stopped working. All speeds were available and it was blowing cold air before the malfunction. It was blowing fine, shutdown, sat overnight, and the blower would not come on after it was started the next day. This vehicle is equipped with the temperature control option for the climate controls.
I've checked the fuses and relays, they're good. The fuses are intact and the relay was swapped with a known good unit.
Is there anything else to check before getting out the multimeter? I'd suspect the blower resistor, except the fan is not even working on high.
I've been cruising the forums, sounds like it might be the fan controller (present when equipped with automatic temperature control, in the same location the resistor would be otherwise). It's under the hood on the passenger side, on the firewall under two heater hoses which have to come off to get at it, to the right of the blower motor itself if you're facing towards the rear of the vehicle.
There was no ground on the blower motor connector, which indicated a bad blower speed control module. Module replaced with the redesigned part. Blower now works.