Aprilaire Model 8570 - Manual (Page 29)

Symptom Cause
Miswiring – Check wire colors to verify I- at AHC is connected to I- at
thermostat and I+ is connected to I+.
No RH display, no outdoor AHC power source – When wired to the Model 8570 thermostat, the AHC
temperature display must be wired to a continuously ON power source. Use voltmeter to verify
presence of 24VAC (nominal) at AHC.
AHC not operating correctly – check red diagnostic light on AHC.
No RH display, outdoor temperature OK No valid reading available – run fan for at least 40 seconds.
RH display, outdoor temperature @ 20°F AHC set for manual mode of operation. Wire an outdoor sensor to the AHC
or wire an outdoor sensor to the thermostat.
- 25 -
TROUBLESHOOTING – AHC CONNECTION