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RH77 · 05-19-2008, 12:44 AM

So, I spent most of the evening trying to diagnose the low fan speed issue for the A/C

I cracked-open the furnace blower cover and found the schematics. According to the wiring, the relays should allow full speed in A/C. It wasn't working. The wiring made no sense either -- color-coded motor wires weren't translating into expected speed output. The circuit board was thought to the be culprit.

Thanks to HVAC-Talk.com, the techs there helped trace it back to the thermostat. There was a dual-speed dip-switch that needed flipped. In the meantime, I ran all current through the "heat" side of the relay since the board was likely slowing it down unnecessarily. It was an intimidating looking SPDT switch relay, but had the strongest output at the heat connector.

Now, I'm pleased to report actual flow of cool air in the upper floor, corner of the house.

Why this whole essay?

The higher speed pulled a LOT of humidity out of the house and cooled it down in a reasonable amount of time.

Bottom Line: The Cool-N-Save. Determining savings will be tough without an unmodified baseline. If it's more (using last years climate data), then we know that either 1) the blower is using more juice, or 2) the CNS is BS.

Stay Cool

RH77

EDIT: Safety First -- I disconnected the power at the breaker box first. Just if someone goes fooling with wires.

05-19-2008, 12:44 AM	#42 (permalink)
RH77 Depends on the Day Join Date: Nov 2007 Location: Kansas City Area Posts: 1,761 Teggy - '98 Acura Integra LS Sports Cars 90 day: 32.74 mpg (US) IMA - '10 Honda Insight EX Team Honda 90 day: 34.76 mpg (US) Tessie - '06 Acura TSX Base 90 day: 28.2 mpg (US) Thanks: 31 Thanked 41 Times in 35 Posts	So, I spent most of the evening trying to diagnose the low fan speed issue for the A/C I cracked-open the furnace blower cover and found the schematics. According to the wiring, the relays should allow full speed in A/C. It wasn't working. The wiring made no sense either -- color-coded motor wires weren't translating into expected speed output. The circuit board was thought to the be culprit. Thanks to HVAC-Talk.com, the techs there helped trace it back to the thermostat. There was a dual-speed dip-switch that needed flipped. In the meantime, I ran all current through the "heat" side of the relay since the board was likely slowing it down unnecessarily. It was an intimidating looking SPDT switch relay, but had the strongest output at the heat connector. Now, I'm pleased to report actual flow of cool air in the upper floor, corner of the house. Why this whole essay? The higher speed pulled a LOT of humidity out of the house and cooled it down in a reasonable amount of time. Bottom Line: The Cool-N-Save. Determining savings will be tough without an unmodified baseline. If it's more (using last years climate data), then we know that either 1) the blower is using more juice, or 2) the CNS is BS. Stay Cool RH77 EDIT: Safety First -- I disconnected the power at the breaker box first. Just if someone goes fooling with wires. __________________ *“If we knew what we were doing, it wouldn't be called research” ― Albert Einstein* _ _ Last edited by RH77; 05-19-2008 at 12:46 AM.. Reason: Safety First