Lighting hit very close to our house and caused damage to our modem and other pc. Since then, our fan to our Central air does not turn off. The only way to get it to turn off is cutting power to it. Anyone know if there is a easy do-it ourself way to fix this?






















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Is it affecting just the evaporator unit (inside) or the condensing unit (outside)? Without looking at the system to diagnose it I would say 1; inside only. probably fryed the thermostat; outside or both, probably a stuck contactor.

The contactor relay in the outside unit is a double pole contact that supplies 240V to the compressor and condensing fan (outside unit). Usually there is a start-up capacitor for the compressor and fan motor, it's a dual capacitor, a cylindrical looking device that stores voltage, and basically "jump starts" the compressor and fan. Never touch one, even with the power off. Usually when a cap goes bad, these devices fail to start. If the outside contactor was fried, stuck energized, you would hear the compressor humming, and it would likely get very cool in the house. By the way, if you go poking around in the outside unit, kill the power. The knife switch or breaker is usually right close to the unit. The thermostat's job is to send low voltage AC (typically 24 VAC) to the outside unit's contactor relay. It also sends a signal to the blower motor in the air handler (inside unit)
The inside blower motor in the Air Handler, is controlled by an electronic timer, usually mounted on a printed circuit board. It is usually set up to keep the blower motor running a few minutes after the outside unit shuts off. This is done for efficiency, as the evaporator is still rather cold when the outside unit cuts off. Also, there is a protection circuit in there that delays the re-start of the compressor in the outside unit in the event of an intermittent loss of power. Usually they are set to delay restart the compressor for 3-5 minutes. This is so when power is restored, you don't put massive surges on the system. I would check the electronic controls in your air handler. They are sensitive to transient pulses.

I would check my address book for the number of my A/C service company......

I have a service contract for all my appliances, which includes the 2 A/C's. The only time i crack the covers on them is if i'm desperate, like a Saturday, when you can't even make a service call till Monday morning. The high temps have both A/C's working overtime. Had 1 gas failure, a couple of starter caps, and 2 contactor relays. I was able to repair 1 relay by cleaning the contacts. Once a lizard got in there and fried himself, and my contactor relay. My A/C's are what i call "entry level" units, not a super high priced deal, 14 SEER, but they are coming up on 7 years old. I have a split floorplan, and the house originally had 1 4 ton unit, which was very ineffective at cooling the house. We re-engineered it with a 3 1/2 ton, and a 2 ton, and split the duct work so it cools more evenly. A few more returns would make it better, i'm too lazy to go in the attic.