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7.0 DIAGNOSTICS
Problem
Blower motor will not
operate or no air-flow
• Failed run capacitor (H voltage only)
• Failed motor (replace)
• Loose wiring connection or broken wire (check
connections & wiring)
• Failed transformer on outdoor unit (replace)
• Circuit breaker or fuse is turned off or has tripped due to
overcurrent or shorted circuit (check for shorts, reset
breaker)
• Belt loose, broken, or off (adjust or replace belt)
• Corrupted VFD program (reprogram)
• Failed VFD (replace)
Excessive vibration
• Blower wheel out of balance (replace or clean blower
wheel)
Water overflowing drainpan
• Plugged drain (clear drain)
• Unit not level (level unit)
Electric heater not heating
properly or not heating at all,
but blower motor is operating
• Over temperature limit has tripped (check for low
air-flow)
• Over temperature limit has failed (replace)
• Contactor has failed (replace)
• One or more heating elements have burned out (replace)
Coil is frozen up
• System low on refrigerant charge (check for leaks and
adjust charge)
• Dirty return air filter (replace filter)
• Inadequate air-flow due to incorrect blower sheave
adjustment (adjust sheave to achieve proper air-flow) or
excessively restrictive duct system (correct duct system)
• Belt loose, broken, or off (adjust or replace belt)
Excessive air-flow
• Incorrect blower sheave adjustment (adjust sheave to
achieve proper air-flow)
Water blow-off from coil
• Excessive air-flow (adjust sheave to achieve proper
air-flow)
• Contaminants on coil fans (clean coil)
• Damaged coil fins (comb out fins or replace coil)
TXV not controlling properly
• TXV bulb not positioned correctly or clamp not tight
(Check position of TXV sensing bulb and tightness of
clamp)
• Failed TXV (replace)
• Plugged TXV inlet screen (clean or replace screen or
replace TXV)
Possible Cause (Suggested Fix)
