My fan runs as soon as I put in the battery.Hyundai accent2001

It is easier to cool a warm engine that to cool an engine at almost over heat condition. So manufacturers run the fan as soon as the engine gets to operating temperature and that gives the cooling system more control of the heat in the system

Radiator fan or AC fan? If its the radiator fan, you need first to check if its motor us OK. You can do this by hardwiring the electricl plug directly to the battery. Motor should run. If it doesn't, then this motor (fan) needs replacement.

If the motor runs fine when hardwiring, then you should have the car scanned for error codes. It is probably that the ECT (engine coolant temp sensor) is bad, thus the ECM never gets the signal "hey, I'm getting hot, turn on the radiator fan!"

disconnect the neg. battery and clean the connectors ECM

Unplug it & check power to the blower
& try battery voltage to the blower

Doesn't matter how you put power to
a blower or fan they are dc motors &
run either direction

check see if cooling fan running could have faulty cooling fan relay or fuse.if cooling fan dont run when ac on car will overheat.AC COMPRESSOR PUT LOAD ON ENGINE.

Check your radiator cooling fans to make sure they're coming on when thy're suppose to. As soon as you tur on the ac, on the radiator fan should come on. If it does try wiggling the wires for the fan to make sure it's not an intermittent problem(be careful, fan may be off and start unexpectedly).

I would have the whole charging system tested with a Volt Meter before you change anything else. You can test the Alternator with a Volt Meter while the engine is running. The Alternator should be putting out between 13-14 volts, anything less and you have a bad Alternator. Check all Battery, Starter, Ground connections for loose or corroded wires and tighten or clean as needed.

Check the fuel pump fuse and relay.

Under the dash fuse box ,fuse 15 (TCM ECT) is a combination of cluster, heater and headlights.probably a relay fuse!!!!! fuse 16is a relay fuse.

you have a bad fan swtich in the block or the therostat housing its an easy fix