A/C unit fan not turning ON, get HOT

[jochoaee]

I need help troubleshooting my A/C. Last night, I got home and my entire house was hot. I looked at my thermostat at it was reading 84F (set point is 78F), but the A/C appeared to be running and not cooling. I went outside to look at the A/C unit and notice that the entire unit was HOT and the fan was not running. I turned off the unit for the night to prevent any further damage. This morning I turned the unit back on (Set FAN to ON position and switch to COOL). I saw the unit's fan turned on but after about 5 minutes and it turned off and seemed to be getting hot. Any suggestions anybody??

P.S. I had the fan motor replaced about 16 months ago.

thanks, jose

[LazyPup]

First off i would like to clairify one point, the fan/auto selector on the thermostate controls the inside blower fan only, it has nothing to do with the fan on the condensing unit outside.

When the thermostat is set to cool, the inside fan motor and the condensing unit, both compressor and fan start.

You stated that when you turned the system on the condensing unit compressor and fan started, then the fan motor overheated and stopped in a short time.

Normally when the fan motors overheat it is a result of one of two problems, either defective bearings in the fan motor, or more commonly a defective fan motor capacitor.

Begin by turning the power to the condensing unit off at the service disconnnect or the breaker. (VERY IMPORTANT: There are two breakers for your AC system, one for the inside unit and another for the outside unit. If you turn the power off at the electrical breaker you must measure the voltage across the primary terminals of the condensing unit contactor to insure you got the correct breaker turned off before attempting any service.)

Open the cover to the fan section and rotate the fan blades by hand. It it spins freely and no notciable wobble on the shaft the bearings are probably good.

Next, locate the fan motor capacitor in the compressor section electrical compartment. (normally there is a label on the inside of the cover that will indicate the layout of the components and there should also be an electrical schematic drawing.)

There should be two capacitors, one for the compressor and one for the fan motor.

DO NOT TOUCH THE CAPACITOR UNTIL YOU HAVE DISCHARGED IT, capacitors can store energy for weeks after they have been taken out of a circuit.)

Begin by locating the wires from the fan motor and follow them to the capacitor. The fan capacitor wire should be a brown wire, and their may be another brown wire with a white stripe.

Again, test the voltage at the contactor to insure the power is off, then using and old screwdriver that has a good insulated handle touch the tip of the screw driver across both poles of the capacitor to disharge it. You may see a small spark, that is ok.

Note the color and position of the wires attached to the capacitor, then remove the wires.

Using an analog (needle type, not a digital) ohm meter set on its highest ohm scale, touch the probes to the two terminals on the capacitor. If the capacitor is good the needle should rise quickly to about mid scale, then fall off slowly back to zero.

Reverse the probes and repeat the test, you should get the same result. If the needle rises and falls off the capacitor is okay.

If the needle does not move the capacitor is open--replace the capacitor.

If the needle moves to full scale and stays the capacitor is shorted and will need replacing.

If the capacitor checked okay and there were no broken wires the problem is in the fan motor. change the motor.