How Can I get my 2003 pontiac grand Prix cooling fans to work ?

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Check relays and fuses. Possible ECM/PCM driver is bad.

through the top. The fan usually has to be removed along with the fan shroud.

most of the time its in the radiator (side tanks)

The fan resistor block is usually located under the passenger side dash, on the side of the heating/cooling assembly. It is located there so the air blowing threw the duct will cool the resistor block to keep the wires from melting. If you don't readily see it by looking under the dash, you may have to remove the glove box to find it - hope this helps - good luck :O)

Yes. Remove the housing (not the hose) and you'll find the thermostat.

you need to replace the resistor
it's on the right side under the dash

the fan motor could just be bad, you can test this by removing the fan and connecting a wire to each terminal and to a battery. the wires hooked up one way will spin the fan and the other way will spin the fan backwards so you cant hook it up wrong. I hope that helps you out!

You would need to buy a factory service manual for that blend door diagram. Try eBay for a used manual set.

You probably need to replace the blower motor resistor. Located on the blower motor below your glovebox. about $25 for the resistor.