98 Volvo S70 Electric fan stays on

I have a 1998 Volvo S70. My electric fan stay on after I shut off the car for about 5 mins or more. I can actually go into it before its been ran and turn the key on motor off and then shut it off and the fan stays running for a few mins. Never did that before. I changed out the tempature switch but nothing. I actually have a tempature code coming up which is causing my check engine light to stay on. If I erase the code the light shuts off but within a min its back on with the same code saying something that the voltage too low. Brand new sensor but still no fix.
Any ideas anyone...please. Battery keeps running low and its brand new and I know its cause of the fan

Thanks!!

Low voltage could also mean no voltage. I'd check the wiring near the temp. switch. Does your car have a coolant temp gauge? If so, does it work? If the gauge isnt working, the wires are probably broken somewhere.

Actually from what my brother in law tells me is that the gauge now doe work better since the replacement so Im guessing it isnt a broken wire?