First off let me say thank you for providing this forum to help out us non-AC repair professionals.

I have a twenty-something year old International split system unit. It cools excellently when it works.

But here’s the problem: About a month ago I noticed that the house was getting warm. The outside compressor/fan unit was running fine but there was very little air coming out of the vents. I went under the house to inspect the blower fan and it was turning, although it did not appear to be at full speed. Without even thinking about the run cap, I assumed it was the blower motor itself. The motor was replaced the next day with a FASCO D721 ¼ hp, 1075 RPM, 3 speed motor. This motor called for a 5 MFD / 370 VAC cap, which was also replaced at the same time. The only difference was that they gave me a 5MFD / 440VAC cap (instead of 370 VAC), and they assured me that this cap would work fine and that the 470 VAC was simply the most that the cap could handle.

Anyway, the blower motor and cap were both replaced, and the AC seemed to work fine for about a week. A second problem then arose, in that the unit began to shut off before the thermostat told it to. If I had the thermostat set on 76 degrees, the entire unit might shut off at 78 or so. When I looked at the thermostat immediately after the unit stopped, it was flashing the compressor icon (as if it had experienced a power failure and now the compressor safety was engaged). The unit would then kick back in after the safety time had elapsed, but would only run for a period of time and then repeat this process.

After scratching my head for a few days, I then replaced the fan center itself, as the relay appeared to be getting hotter than it should have been getting (in my unprofessional opinion, anyway). This particular fan center contained the transformer for 24vDC power and the fan relay both mounted on a double gang electrical box plate/cover. The fan center was matched up value for value at the HVAC store and it was an exact replacement.

Now the entire unit has worked wonderfully for the last three weeks . . . until 2 days ago when I again noticed that there was very little air coming out of the vents (outside unit still chugging along faithfully). Since almost everything was practically brand new, I assumed that the run capacitor had failed. I got the exact replacement that the motor called for (5 MFD / 370 VAC) and replaced it 2 days ago. Just for grins and giggles, I also replaced the thermostat (only a 4 wire) at the same …read more

Source: DoItYourself.com