well I pulled the air handler cover off today, saw the wiring diagram that shows the thermostat wiring and case grounding etc., and it shows a bundle of wires/plug that represents the speed control circuit/s but doesn't show any detail on them at all. the wiring diagram was on another little cover and under that was a transformer, a large bundle of wires and a circuit board with 8 DIMM switches. All down but #7 up. The chart on the blower motor said;1-off and 2-off meant my outdoor unit is a 3 ton which it is. the largest on the chart.3-off and 4-off meant my airflow setting was on "normal" at 400 cfm/ton.5-off and 6-off meant my cooling off delay was selection-none, nominal airflow-100%. Not exactly sure what all that means.7-on and 8-off meant my aux heat airflow was "med-high" 1125 CFM.I put #3 up/on to get airflow setting "HIGH" 450 cfm/ton, 150 CFM total gain, but that only changes the speed when it's cooling and compressor running. It does blow noticeably faster though.I put the #7 switch down/off to set my aux-heat airflow to "high", 1350 CFM. It did not change the speed of the ON fan speed at all, with thermostat switch set to COOL or OFF, and I'm not about to put the HEAT on to test that speed, cause it was already getting hot enough in the house with the AC off in south florida! LOL! I left aux-heat speed on high though, just because. I would have liked if I could have tricked my air handler into thinking there was a bigger unit outside to get a bigger tonnage multiplier on my CFM for cooling, but nope! already have the biggest!So... the fan speed still ramps down A LOT when the cooling compressor circuit gets denergized and it just runs on ON fan speed. I had previously guessed it to be at about 80-90% but I was just noticing the difference at the vents before. Actually standing next to the air handler, you can hear that it really slows down a lot. Probably 50% or lower.There is no wiring diagram that shows what the wires in the large bundle of wires are, but I'm sure it's probably as simple as jumping 2 of those wires together to get 100% fan speed? either hardwired or with a switch in between? and either manually controlling that switch or finding something else to control it such as one of the thermostat wires and a contactor/relay? even if I just end up with a manual switch on the side of the air handler to bypass the speed control I'd be fine with that. I really only have a problem with the heat build up during the summer months when I'm gaming and multiple ppl in the room, so I could just go in the closet and flip the switch on when I need it.EDIT: ok I have since learned that the cooling off delay keeps the blower motor blowing faster for a while after the compressor gets shut off. It's on no delay now. my other options are;5-on and 6-off = 90 sec delay / 100% airflow5-off and 6-on = 180 sec delay / 50% airflow5-on and 6-on = ENHANCE / ENHANCEI tried all the settings and can't figure out what the enhance setting is, but it doesn't keep the fan running full speed when compressor is turned off. The 90 sec delay DOES keep the blower motor blowing full speed for 1.5 minutes after compressor shuts off. The 180 sec delay keeps the fan running at the same 50% ON speed that I hate for 3 minutes if set to AUTO. If set to ON it just keeps going 50% like it always does. I want to find a way to extend that 90 sec delay at 100% airflow, indefinitely.
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In my experience, the choice of direction determines where the inevitable dust build-up will occur. Dust seems to accumulate wherever the air enters the case.
With fans blowing in, you tend to get the most dust build up right in front of the fan. You wouldn't want this happening on the heat sink of your CPU, as the dust acts like an insulating blanket.
On the other hand, with fans blowing out, you get dust in the case near every possible way for air to get in. One place this can be a problem in a PC is when the air comes in through the openings for removable drives.
Probably the best design I've seen involves having two fans, one blowing in and the other out. The exhaust fan sits near the heat sink of the CPU to ensure good air flow there, w/o the dust problem, and the other fan pulls air into the case to keep the pressure in the case high enough to prevent sucking air (and dust) in through all the other openings.