The fan blower stays on after I have turned off the AC & heater.

If you have a fan that has different speed settings (1234, or low med high etc) and the only one that works is high - then the blower resistor pack has failed. If you have a climate control unit (where you just pick a temp you want) then the fan is controlled by the heating system and it sets fan speed. If you have climate control style try lowering the temp to a lower setting (current temp in vehicle) and see if fan slows down. If not then climate control unit or fan resistor bad. If dial type and you get nothing on lower settings (only high works like mentioned above) you need to change blower resistor. It is located under dash near the fan itself. Look for small unit bolted in duct near fan with wire plug going to it.

try to unplug the resistor blower fan resistor. if fan shut off replace the resistor bank/

sometimes,and some cars have a blower motor resistor that goes bad.Check and see if you have one,replace

Sounds like someone needs to do some more troubleshooting first. Changing the cluster is not a simple matter since your mileage will be different. And the cluster is on a different circuit that the ac so one should not affect the other.

Due to the age of your vehicle, the brushes in the fan motor are worn out. you will have to replace the fan motor, it is not serviceable.

You may need a resister for the heater fan motor.

I would need more info to give any advice.
I assume you mean the blower for the ac and heater.
How is it not working but works on high ?
And what power are you turning off that makes it blow harder ?

First check the 15 amp HVAC fuse located in the main fuse block inside the car on the passenger side of the center console, under a cover. If the fuse is good, then the problem may either be the HVAC blower switch (which is the fan blower selector switch), the fan blower motor resistor, or the fan blower motor. An auto repair manual will explain and illustrate for you the steps on how to check each of these components.

Even after pushing the ac light switch on, the fan blower selector switch has to be turned on as well (working) because it provides an electrical path to the positive side of the battery to complete the circuit and turn the ac light on. What the ac light switch does is provide the electrical path for the ac compressor clutch to come on through the ac control relay which is controlled by the car's PCM(computer) when you want ac, but the ac light switch still needs to run through the fan blower selector switch to receive its power. You can turn on the fan without the ac light switch because it gets its ground path(negative) from the blower motor. So the blower motor has to work in order to provide a ground path for the fan blower selector switch to be functional. You could have a faulty blower motor which is why no air blows through the vents. The fan blower motor is located inside the car on the passenger side underneath the dash at the bottom end of the glove compartment box. You'll see it. It's right above where a person rests their feet on the floor. Therefore, if your 15 amp HVAC fuse is good, check to see if you have voltage at the blower motor connector. Unclip the connector and with the ignition on and the fan blower switch moved to any one of the first 3 selections, check for voltage using a multimeter. The voltage will vary because there is a blower motor resistor. Voltage should be higher on setting 3 than 1. If you do have voltage at the blower motor connector, check for a faulty blower motor. The auto repair manual will tell you how to do it using jumper wires.

It's normal that your car is running hot because the radiator fan works in conjunction with your ac compressor. If the ac is on, the radiator fan will be on and therefore the engine coolant temperature will stay in it's normal operating range. If the ac is off, the radiator fan will stay off as well and the engine coolant temperature gauge will begin to rise and show pretty hot (especially at idle). It will do this up until a certain degree then the radiator fan should turn on thermostatically and stabilize the temperature. It's scary and I know what your saying because it does that to my car if my ac isn't on. Don't worry it won't overheat.

If it is eatc ,the blower speed controller is probably shorted to power ,causing the blower to stay running with the a/c off.

blower motor,relay fuse