I am trying to wire a extra fan motor in and I am looking for a hot wire on when the truck is running that can support 40 amps 1989 chevy 2500 4x4 5.7

hot terminals and dead battery indict a very high discharge like a dead short in the lectrics

Another possibility is a restriction in air flow thru the radiator. The condenser puts extra heat thru the radiator with the ac on.

Its either the fan switch is bad,,or a fuse,,or the fan motor its self is bad,I would check fuse 1st,,2nd unplug fan motor run a hotwire to it and see if it turns,,if it does than you know its the switch for the fan. If it dont turn with separate hot wire ,,than its the fan go bad.

I had a similar problem. Is your temperature gauge pegged to the right as very hot? Or reads always cold, even when hot. If it is a 3100 motor their is a coolant temperature gauge sending unit under the air breather intake that is right next to where you replace the thermostat.

Get a haynes repair manual at a parts dealer, Amazon, or your public library.
On the Chevrolet Lumina, Monte Carlo, & Impala FWD 1995 to 2005 it's under section 3-8 on page 3-6. It goes into great detail, and it's too complicated to explain here. If your sensor is bad, but the wires and fuses are good then the fans won't run.

Your second fan only runs when the air compressor is turning, If your ac compressor is not running then the sensor will not have the passenger fan run.
You have to see if the fan motors are good and then the wiring is good, and no fuses blown. You might blow fuses so have extra blue ones if I remember right. Recheck fuses after testing.

CHECK COOLING FAN FUSE AND RELAY.IF BOTH ARE GOOD.HOT WIRE COOLANT FAN.IF FAN DONT RUN FAN MOTOR NEEDS REPLACING. IF FAN MOTOR RUN WHEN YOU HOT WIRE IT.YOUR FAN MOTOR ELECTRICAL WIRES DAMAGED OR HAS SHORTS OR THE COOLANT TEMPERATURE SENSOR FAULTY.

try to see if ur heater core is pluged up sumtimes that can cause ur car to over heat. hope this helps

Have you had the blower motor switch replaced? I had a Chevy Silverado and the low worked but no other settings. It is a pretty quick fix and reasonably cheap.

IT IS LOCATED ON DRIVER SIDE OF ENGINE BEHIND THE THERMOSTATE HOUSEING IT HAS TWO WIRES YELLOW AND BROWN HOPE THIS HELPS .
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there is a fan control relay under the dashboard with the other relays check that then check the temperature contreol module theat is located in the engine compartment
--------------- there is a 2 speed sensor/sender on the lower part of the radiator, facing the driver. It's on the tube at the end of the radiator. The fan motor has three leads, an orange, which should be hot, and is monitored by a 40 amp fuse located either on top of the battery, or with the fuse modules/relays under the dash. (according to the book, I still can't find mine, it may be NEXT to the battery. The negative must be thru the chassis, so it would be a good idea if, at temperature, with two hots going to the motor, look for a shorted ground. If one of the hots isn't, then the sensor or 40 amp is bad. After those are ruled out, it's the motor.

use a test light the wire from the battery should be hot all the time the wire that goes to the solenoid should be hot when the key is turned over to start and the wire going to the coil should be hot when the key is in run.