I'll try the cigarette lighter trick tomorrow. I hope the one in the Merc fits because the Focus' is missing. Maybe the light being on all the time is what it does if it can't detect a complete circuit to the OBD port...? Like a fall back procedure or something. My guess would be thermostat or a slightly messed up fan resistor... There are no leaks under the car after sitting over night. I've gotten under it and seen nothing wet either. Water pump is an interesting one to. Worn impellers? Only pumps enough coolant to keep the engine cool above 1000rpm maybe? I haven't lost any coolant after 3 days of driving so I'm not sure of the head gasket. I went through that with the Ranger. I noticed it pretty quick.