I have a fairly new AC system installed. The outside unit is 3 years old, the air handler is 2 years old. They were replaced a year apart due to failure. Last summer, the dual run capacitor on the outside unit swelled and failed, causing the compressor to be able to start, but the fan wouldn't run. It only did it a couple of times over a 24 hour period before it was discovered. The dual capacitor was replaced, and the unit kicked on and ran fine for the remainder of the year.

Fast forward to 7 days ago or so. The AC will kick on at the preset temperature, and it will begin to cool; however, the light dim every 3-4 minutes like the compressor is trying to kick back on. When the outside unit first comes on at temp, the lights dim considerably more than what I'd deem to be "normal". The unit then does its cycle of off/on for about a half-dozen cycles, then it runs fine until it gets back down to the proper temperature. I should probably note that the outside fan continues to run unaffected at full speed during this entire process.

The air handler is in the attic--it is a Bryant unit, and seems to be fine. The outside unit is a Fedders, which I now understand is considered to be bottom of the line. Our haste to get the unit swapped out on a 105 degree day cost us dearly. What could be causing the problem, and what are my repair options?

If everything is installed right and the breaker box is big enough to handle the load,, the compressor SHOULD Not cause your lights to dim at all, what size in AMPS is your breaker box? Is your airhandler electric? Or gas heat? How many double pole breakers are in the box? And what do they supply, it sounds to me like you have more of an electrical problem rather than a AC prob.

The compressor is on a 30A breaker. I live in an 80 year old house with 2 panels. We rewired the entire house 2 years ago to even the load. The house has a 100A main, which feeds the main panel of 8 DP breakers, with all but 2 being double pole. There is a 60A double to feed the secondary panel, a 30A double for the dryer, a 30A double for the AC compressor, a 30A double for the water heater, a 20A single for our mother-in-law quarters, and a 20A single for the air handler (gas heat). There are two twins in the box (30/20), but neither the water heater nor the dryer are on at the time.

As for the lights, they have always dimmed just a little, which I expect. That unit is a huge load all at once on a small service like we have. Keep in mind, this unit has run for 3 years without issue (except the capacitor last summer).

Electrical load is always a concern, but we have very little on in the evening--clothes drying is in the early morning, as is hot water usage. It's a 3 ton unit using the "old standard" R12 (yes, we got screwed). However, this should still not cause the compressor to kick off and on, leaving the air handler and compressor fan running unaffected. Could low/high freon load be a culprit? I'm afraid to call out a tech because of the 36" of blown-in insulation we had put in last year. The air handler is dammed off, but it's 40' from the scuttle hole, so the tech will have to stomp through to get to it.